/*
 * repos.c: mod_dav_svn repository provider functions for Subversion
 *
 * ====================================================================
 *    Licensed to the Apache Software Foundation (ASF) under one
 *    or more contributor license agreements.  See the NOTICE file
 *    distributed with this work for additional information
 *    regarding copyright ownership.  The ASF licenses this file
 *    to you under the Apache License, Version 2.0 (the
 *    "License"); you may not use this file except in compliance
 *    with the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing,
 *    software distributed under the License is distributed on an
 *    "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *    KIND, either express or implied.  See the License for the
 *    specific language governing permissions and limitations
 *    under the License.
 * ====================================================================
 */

#define APR_WANT_STRFUNC
#include <apr_want.h>
#include <apr_strings.h>
#include <apr_hash.h>
#include <apr_lib.h>

#include <httpd.h>
#include <http_request.h>
#include <http_protocol.h>
#include <http_log.h>
#include <http_core.h>  /* for ap_construct_url */
#include <mod_dav.h>

#define CORE_PRIVATE      /* To make ap_show_mpm public in 2.2 */
#include <http_config.h>

#include "svn_hash.h"
#include "svn_types.h"
#include "svn_pools.h"
#include "svn_error.h"
#include "svn_time.h"
#include "svn_fs.h"
#include "svn_repos.h"
#include "svn_dav.h"
#include "svn_sorts.h"
#include "svn_version.h"
#include "svn_props.h"
#include "svn_ctype.h"
#include "svn_subst.h"
#include "mod_dav_svn.h"
#include "svn_ra.h"  /* for SVN_RA_CAPABILITY_* */
#include "svn_dirent_uri.h"
#include "private/svn_log.h"
#include "private/svn_fspath.h"
#include "private/svn_repos_private.h"
#include "private/svn_sorts_private.h"

#include "dav_svn.h"


#define DEFAULT_ACTIVITY_DB "dav/activities.d"


struct dav_stream {
  const dav_resource *res;

  /* for reading from the FS */
  svn_stream_t *rstream;

  /* for writing to the FS. we use wstream OR the handler/baton. */
  svn_stream_t *wstream;
  svn_txdelta_window_handler_t delta_handler;
  void *delta_baton;
};


/* Convenience structure that facilitates combined memory allocation of
   a dav_resource and dav_resource_private pair. */
typedef struct dav_resource_combined {
  dav_resource res;
  dav_resource_private priv;
} dav_resource_combined;


/* Helper-wrapper around svn_fs_check_path(), which takes the same
   arguments.  But: if we attempt to stat a path like "file1/file2",
   then still return 'svn_node_none' to signal nonexistence, rather
   than a full-blown filesystem error.  This allows mod_dav to throw
   404 instead of 500. */
static dav_error *
fs_check_path(svn_node_kind_t *kind,
              svn_fs_root_t *root,
              const char *path,
              apr_pool_t *pool)
{
  svn_error_t *serr;
  svn_node_kind_t my_kind;

  serr = svn_fs_check_path(&my_kind, root, path, pool);

  /* Possibly trap other fs-errors here someday -- errors which may
     simply indicate the path's nonexistence, rather than a critical
     problem. */
  if (serr && serr->apr_err == SVN_ERR_FS_NOT_DIRECTORY)
    {
      svn_error_clear(serr);
      *kind = svn_node_none;
      return NULL;
    }
  else if (serr)
    {
      return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                  apr_psprintf(pool, "Error checking kind of "
                                               "path '%s' in repository",
                                               path),
                                  pool);
    }

  *kind = my_kind;
  return NULL;
}


static int
parse_version_uri(dav_resource_combined *comb,
                  const char *path,
                  const char *label,
                  int use_checked_in)
{
  const char *slash;
  const char *created_rev_str;

  /* format: CREATED_REV/REPOS_PATH */

  /* ### what to do with LABEL and USE_CHECKED_IN ?? */

  comb->res.type = DAV_RESOURCE_TYPE_VERSION;
  comb->res.versioned = TRUE;

  slash = ap_strchr_c(path, '/');
  if (slash == NULL)
    {
      /* http://host.name/repos/$svn/ver/0

         This URL form refers to the root path of the repository.
      */
      created_rev_str = apr_pstrndup(comb->res.pool, path, strlen(path));
      comb->priv.root.rev = SVN_STR_TO_REV(created_rev_str);
      comb->priv.repos_path = "/";
    }
  else if (slash == path)
    {
      /* the CREATED_REV was missing(?)

         ### not sure this can happen, though, because it would imply two
         ### slashes, yet those are cleaned out within get_resource
      */
      return TRUE;
    }
  else
    {
      apr_size_t len = slash - path;

      created_rev_str = apr_pstrndup(comb->res.pool, path, len);
      comb->priv.root.rev = SVN_STR_TO_REV(created_rev_str);
      comb->priv.repos_path = slash;
    }

  /* if the CREATED_REV parsing blew, then propagate it. */
  if (comb->priv.root.rev == SVN_INVALID_REVNUM)
    return TRUE;

  /* We have idempotent resource. */
  comb->priv.idempotent = TRUE;

  return FALSE;
}


static int
parse_history_uri(dav_resource_combined *comb,
                  const char *path,
                  const char *label,
                  int use_checked_in)
{
  /* format: ??? */

  /* ### what to do with LABEL and USE_CHECKED_IN ?? */

  comb->res.type = DAV_RESOURCE_TYPE_HISTORY;

  /* ### parse path */
  comb->priv.repos_path = path;

  return FALSE;
}


static int
parse_working_uri(dav_resource_combined *comb,
                  const char *path,
                  const char *label,
                  int use_checked_in)
{
  const char *slash;

  /* format: ACTIVITY_ID/REPOS_PATH */

  /* ### what to do with LABEL and USE_CHECKED_IN ?? */

  comb->res.type = DAV_RESOURCE_TYPE_WORKING;
  comb->res.working = TRUE;
  comb->res.versioned = TRUE;

  slash = ap_strchr_c(path, '/');

  /* This sucker starts with a slash.  That's bogus. */
  if (slash == path)
    return TRUE;

  if (slash == NULL)
    {
      /* There's no slash character in our path.  Assume it's just an
         ACTIVITY_ID pointing to the root path.  That should be cool.
         We'll just drop through to the normal case handling below. */
      comb->priv.root.activity_id = apr_pstrdup(comb->res.pool, path);
      comb->priv.repos_path = "/";
    }
  else
    {
      comb->priv.root.activity_id = apr_pstrndup(comb->res.pool, path,
                                                 slash - path);
      comb->priv.repos_path = slash;
    }

  return FALSE;
}


static int
parse_activity_uri(dav_resource_combined *comb,
                   const char *path,
                   const char *label,
                   int use_checked_in)
{
  /* format: ACTIVITY_ID */

  /* ### what to do with LABEL and USE_CHECKED_IN ?? */

  comb->res.type = DAV_RESOURCE_TYPE_ACTIVITY;

  comb->priv.root.activity_id = path;

  return FALSE;
}


static int
parse_vcc_uri(dav_resource_combined *comb,
              const char *path,
              const char *label,
              int use_checked_in)
{
  /* format: "default" (a singleton) */

  if (strcmp(path, DAV_SVN__DEFAULT_VCC_NAME) != 0)
    return TRUE;

  if (label == NULL && !use_checked_in)
    {
      /* Version Controlled Configuration (baseline selector) */

      /* ### mod_dav has a proper model for these. technically, they are
         ### version-controlled resources (REGULAR), but that just monkeys
         ### up a lot of stuff for us. use a PRIVATE for now. */

      comb->res.type = DAV_RESOURCE_TYPE_PRIVATE;   /* _REGULAR */
      comb->priv.restype = DAV_SVN_RESTYPE_VCC;

      comb->res.exists = TRUE;
      comb->res.versioned = TRUE;
      comb->res.baselined = TRUE;

      /* NOTE: comb->priv.repos_path == NULL */
    }
  else
    {
      /* a specific Version Resource; in this case, a Baseline */

      svn_revnum_t revnum;

      if (label != NULL)
        {
          revnum = SVN_STR_TO_REV(label); /* assume slash terminates */
          if (!SVN_IS_VALID_REVNUM(revnum))
            return TRUE;        /* ### be nice to get better feedback */
        }
      else /* use_checked_in */
        {
          /* use the DAV:checked-in value of the VCC. this is always the
             "latest" (or "youngest") revision. */

          /* signal prep_version to look it up */
          revnum = SVN_INVALID_REVNUM;
        }

      comb->res.type = DAV_RESOURCE_TYPE_VERSION;

      /* exists? need to wait for now */
      comb->res.versioned = TRUE;
      comb->res.baselined = TRUE;

      /* which baseline (revision tree) to access */
      comb->priv.root.rev = revnum;

      /* NOTE: comb->priv.repos_path == NULL */
      /* NOTE: comb->priv.created_rev == SVN_INVALID_REVNUM */
    }

  return FALSE;
}


static int
parse_me_resource_uri(dav_resource_combined *comb,
                      const char *path,
                      const char *label,
                      int use_checked_in)
{
  /* In HTTP protocol v2, this uri represents the repository itself,
     and is the place where custom REPORTs get sent to.  (It replaces
     the older vcc uri form.)  It has no trailing components.  */

  if (path[0] != '\0')
    return TRUE;

  comb->res.type = DAV_RESOURCE_TYPE_PRIVATE;
  comb->priv.restype = DAV_SVN_RESTYPE_ME;

  /* We're keeping these the same as the VCC resource, to make things
     smoother for our report requests. */
  comb->res.exists = TRUE;
  comb->res.versioned = TRUE;
  comb->res.baselined = TRUE;
  /* NOTE: comb->priv.repos_path == NULL */

  return FALSE;
}


static int
parse_baseline_coll_uri(dav_resource_combined *comb,
                        const char *path,
                        const char *label,
                        int use_checked_in)
{
  const char *slash;
  svn_revnum_t revnum;

  /* format: REVISION/REPOS_PATH */

  /* ### what to do with LABEL and USE_CHECKED_IN ?? */

  slash = ap_strchr_c(path, '/');
  if (slash == NULL)
    slash = "/";        /* they are referring to the root of the BC */
  else if (slash == path)
    return TRUE;        /* the REVISION was missing(?)
                           ### not sure this can happen, though, because
                           ### it would imply two slashes, yet those are
                           ### cleaned out within get_resource */

  revnum = SVN_STR_TO_REV(path);  /* assume slash terminates conversion */
  if (!SVN_IS_VALID_REVNUM(revnum))
    return TRUE;        /* ### be nice to get better feedback */

  /* ### mod_dav doesn't have a proper model for these. they are standard
     ### VCRs, but we need some additional semantics attached to them.
     ### need to figure out a way to label them as special. */

  comb->res.type = DAV_RESOURCE_TYPE_REGULAR;
  comb->res.versioned = TRUE;
  comb->priv.root.rev = revnum;
  comb->priv.repos_path = slash;

  return FALSE;
}


static int
parse_baseline_uri(dav_resource_combined *comb,
                   const char *path,
                   const char *label,
                   int use_checked_in)
{
  svn_revnum_t revnum;

  /* format: REVISION */

  /* ### what to do with LABEL and USE_CHECKED_IN ?? */

  revnum = SVN_STR_TO_REV(path);
  if (!SVN_IS_VALID_REVNUM(revnum))
    return TRUE;        /* ### be nice to get better feedback */

  /* create a Baseline resource (a special Version Resource) */

  comb->res.type = DAV_RESOURCE_TYPE_VERSION;

  /* exists? need to wait for now */
  comb->res.versioned = TRUE;
  comb->res.baselined = TRUE;

  /* which baseline (revision tree) to access */
  comb->priv.root.rev = revnum;

  /* NOTE: comb->priv.repos_path == NULL */
  /* NOTE: comb->priv.created_rev == SVN_INVALID_REVNUM */

  return FALSE;
}


static int
parse_revstub_uri(dav_resource_combined *comb,
                  const char *path,
                  const char *label,
                  int use_checked_in)
{
  /* format: !svn/rev/REVISION

     In HTTP protocol v2, this represents a specific revision in the
     repository.  Clients perform PROPFIND and PROPPATCH against it to
     read and write revprops.  (This uri replaces baseline (bln) and
     working baseline (wbl) forms.)
   */

  svn_revnum_t revnum = SVN_STR_TO_REV(path);
  if (!SVN_IS_VALID_REVNUM(revnum))
    return TRUE;  /* fail */

  comb->res.type = DAV_RESOURCE_TYPE_VERSION;
  comb->res.versioned = TRUE;
  comb->res.baselined = TRUE;
  /* exists? need to wait for now */

  /* which baseline (revision tree) to access */
  comb->priv.root.rev = revnum;

  /* all resource parameters are fixed in URI. */
  comb->priv.idempotent = TRUE;

  /* NOTE: comb->priv.repos_path == NULL */
  /* NOTE: comb->priv.created_rev == SVN_INVALID_REVNUM */

  return FALSE;
}


static int
parse_revroot_uri(dav_resource_combined *comb,
                  const char *path,
                  const char *label,
                  int use_checked_in)
{
  /* format: !svn/rvr/REVISION/[PATH]

     In HTTP protocol v2, this represents a path within a specific
     revision.  Clients perform PROPFIND and GET against it to read
     versioned file/dir properties and file contents.  (This uri
     replaces baseline collection (bc) forms.)
   */

  /* Right now, we treat 'rvr' URIs exactly the same as 'bc' ones.
     Same expected format, same utility, etc.  */
  return parse_baseline_coll_uri(comb, path, label, use_checked_in);
}


static int
parse_txnstub_uri(dav_resource_combined *comb,
                  const char *path,
                  const char *label,
                  int use_checked_in)
{
  /* format: !svn/txn/TXN_NAME

     In HTTP protocol v2, this represents a specific uncommitted
     transaction.  Clients perform PROPFIND and PROPPATCH against it
     to read and write txnprops during a commit.  They can also issue
     a DELETE against it to abort the txn.
   */

  if (path == NULL)
    return TRUE;  /* fail, we need a txn_name. */

  comb->res.type = DAV_RESOURCE_TYPE_PRIVATE;
  comb->priv.restype = DAV_SVN_RESTYPE_TXN_COLLECTION;
  comb->priv.root.txn_name = apr_pstrdup(comb->res.pool, path);

  return FALSE;
}

static int
parse_vtxnstub_uri(dav_resource_combined *comb,
                   const char *path,
                   const char *label,
                   int use_checked_in)
{
  /* format: !svn/vtxn/TXN_NAME */

  if (parse_txnstub_uri(comb, path, label, use_checked_in))
    return TRUE;

  if (!comb->priv.root.txn_name)
    return TRUE;

  comb->priv.root.vtxn_name = comb->priv.root.txn_name;
  comb->priv.root.txn_name = dav_svn__get_txn(comb->priv.repos,
                                              comb->priv.root.vtxn_name);

  return FALSE;
}


static int
parse_txnroot_uri(dav_resource_combined *comb,
                  const char *path,
                  const char *label,
                  int use_checked_in)
{
  /* format: !svn/txr/TXN_NAME/[PATH]

     In HTTP protocol v2, this represents a path within a specific
     uncommitted transaction.  Clients perform PUT, COPY, DELETE, MOVE
     against it to modify the path.
   */
  const char *slash;

  /* Note that we're calling this a WORKING resource, rather than
     PRIVATE, so that we can let prep_working() do the same work for
     us that it does on DeltaV 'working resources'.  */
  comb->res.type = DAV_RESOURCE_TYPE_WORKING;

  /* ...but setting this restype can let parse_working() know whether
     this is a !svn/wrk/ (DeltaV) or a !svn/txr (protocol v2) */
  comb->priv.restype = DAV_SVN_RESTYPE_TXNROOT_COLLECTION;
  comb->res.working = TRUE;
  comb->res.versioned = TRUE;

  slash = ap_strchr_c(path, '/');

  /* This sucker starts with a slash.  That's bogus. */
  if (slash == path)
    return TRUE;

  if (slash == NULL)
    {
      /* There's no slash character in our path.  Assume it's just an
         TXN_NAME pointing to the root path.  That should be cool.
         We'll just drop through to the normal case handling below. */
      comb->priv.root.txn_name = apr_pstrdup(comb->res.pool, path);
      comb->priv.repos_path = "/";
    }
  else
    {
      comb->priv.root.txn_name = apr_pstrndup(comb->res.pool, path,
                                              slash - path);
      comb->priv.repos_path = slash;
    }

  return FALSE;
}

static int
parse_vtxnroot_uri(dav_resource_combined *comb,
                   const char *path,
                   const char *label,
                   int use_checked_in)
{
  /* format: !svn/vtxr/TXN_NAME/[PATH] */

  if (parse_txnroot_uri(comb, path, label, use_checked_in))
    return TRUE;

  if (!comb->priv.root.txn_name)
    return TRUE;

  comb->priv.root.vtxn_name = comb->priv.root.txn_name;
  comb->priv.root.txn_name = dav_svn__get_txn(comb->priv.repos,
                                              comb->priv.root.vtxn_name);

  return FALSE;
}


static int
parse_wrk_baseline_uri(dav_resource_combined *comb,
                       const char *path,
                       const char *label,
                       int use_checked_in)
{
  const char *slash;

  /* format: ACTIVITY_ID/REVISION */

  /* ### what to do with LABEL and USE_CHECKED_IN ?? */

  comb->res.type = DAV_RESOURCE_TYPE_WORKING;
  comb->res.working = TRUE;
  comb->res.versioned = TRUE;
  comb->res.baselined = TRUE;

  if ((slash = ap_strchr_c(path, '/')) == NULL
      || slash == path
      || slash[1] == '\0')
    return TRUE;

  comb->priv.root.activity_id = apr_pstrndup(comb->res.pool, path,
                                             slash - path);
  comb->priv.root.rev = SVN_STR_TO_REV(slash + 1);

  /* NOTE: comb->priv.repos_path == NULL */

  return FALSE;
}


static const struct special_defn
{
  const char *name;

  /*
   * COMB is the resource that we are constructing. Any elements that
   * can be determined from the PATH may be set in COMB. However, further
   * operations are not allowed (we don't want anything besides a parse
   * error to occur).
   *
   * At a minimum, the parse function must set COMB->res.type and
   * COMB->priv.repos_path.
   *
   * PATH does not contain a leading slash. Given "/root/$svn/xxx/the/path"
   * as the request URI, the PATH variable will be "the/path"
   */
  int (*parse)(dav_resource_combined *comb, const char *path,
               const char *label, int use_checked_in);

  /* The number of subcompenents after the !svn/xxx/... before we
     reach the actual path within the repository. */
  int numcomponents;

  /* Boolean:  are the subcomponents followed by a repos path? */
  int has_repos_path;

  /* The private resource type for the /$svn/xxx/ collection. */
  enum dav_svn_private_restype restype;

} special_subdirs[] =
{
  /* Our original delta-V-ish protocol uses all these: */
  { "ver", parse_version_uri, 1, TRUE, DAV_SVN_RESTYPE_VER_COLLECTION },
  { "his", parse_history_uri, 0, FALSE, DAV_SVN_RESTYPE_HIS_COLLECTION },
  { "wrk", parse_working_uri, 1, TRUE,  DAV_SVN_RESTYPE_WRK_COLLECTION },
  { "act", parse_activity_uri, 1, FALSE, DAV_SVN_RESTYPE_ACT_COLLECTION },
  { "vcc", parse_vcc_uri, 1, FALSE, DAV_SVN_RESTYPE_VCC_COLLECTION },
  { "bc", parse_baseline_coll_uri, 1, TRUE, DAV_SVN_RESTYPE_BC_COLLECTION },
  { "bln", parse_baseline_uri, 1, FALSE, DAV_SVN_RESTYPE_BLN_COLLECTION },
  { "wbl", parse_wrk_baseline_uri, 2, FALSE, DAV_SVN_RESTYPE_WBL_COLLECTION },

  /* The new v2 protocol uses these new 'stub' uris: */
  { "me",  parse_me_resource_uri, 0, FALSE, DAV_SVN_RESTYPE_ME },
  { "rev", parse_revstub_uri, 1, FALSE, DAV_SVN_RESTYPE_REV_COLLECTION },
  { "rvr", parse_revroot_uri, 1, TRUE, DAV_SVN_RESTYPE_REVROOT_COLLECTION },
  { "txn", parse_txnstub_uri, 1, FALSE, DAV_SVN_RESTYPE_TXN_COLLECTION},
  { "txr", parse_txnroot_uri, 1, TRUE, DAV_SVN_RESTYPE_TXNROOT_COLLECTION},
  { "vtxn", parse_vtxnstub_uri, 1, FALSE, DAV_SVN_RESTYPE_TXN_COLLECTION},
  { "vtxr", parse_vtxnroot_uri, 1, TRUE, DAV_SVN_RESTYPE_TXNROOT_COLLECTION},

  { NULL } /* sentinel */
};


/*
 * parse_uri: parse the provided URI into its various bits
 *
 * URI will contain a path relative to our configured root URI. It should
 * not have a leading "/". The root is identified by "".
 *
 * On output: *COMB will contain all of the information parsed out of
 * the URI -- the resource type, activity ID, path, etc.
 *
 * Note: this function will only parse the URI. Validation of the pieces,
 * opening data stores, etc, are not part of this function.
 *
 * TRUE is returned if a parsing error occurred. FALSE for success.
 */
static int
parse_uri(dav_resource_combined *comb,
          const char *uri,
          const char *label,
          int use_checked_in)
{
  const char *special_uri = comb->priv.repos->special_uri;
  apr_size_t len1;
  apr_size_t len2;
  char ch;

  len1 = strlen(uri);
  len2 = strlen(special_uri);
  if (len1 > len2
      && ((ch = uri[len2]) == '/' || ch == '\0')
      && memcmp(uri, special_uri, len2) == 0)
    {
      if (ch == '\0')
        {
          /* URI was "/root/!svn". It exists, but has restricted usage. */
          comb->res.type = DAV_RESOURCE_TYPE_PRIVATE;
          comb->priv.restype = DAV_SVN_RESTYPE_ROOT_COLLECTION;
        }
      else
        {
          const struct special_defn *defn;

          /* skip past the "!svn/" prefix */
          uri += len2 + 1;
          len1 -= len2 + 1;

          for (defn = special_subdirs ; defn->name != NULL; ++defn)
            {
              apr_size_t len3 = strlen(defn->name);

              if (len1 >= len3 && memcmp(uri, defn->name, len3) == 0)
                {
                  /* If we find a slash after our special subdir, or
                     if we don't and this subdir isn't *supposed* to have
                     anything following it (such as the !svn/me
                     resource), hand off the custom parser for this
                     subdir type. */
                  if (uri[len3] == '/')
                    {
                      if ((*defn->parse)(comb, uri + len3 + 1, label,
                                         use_checked_in))
                        return TRUE;
                    }
                  else if (uri[len3] == '\0')
                    {
                      if ((defn->numcomponents == 0)
                          && (! defn->has_repos_path))
                        {
                          if ((*defn->parse)(comb, "", label, use_checked_in))
                            return TRUE;
                        }
                      else
                        {
                          /* URI was "/root/!svn/XXX". The location
                             exists, but has restricted usage. */
                          comb->res.type = DAV_RESOURCE_TYPE_PRIVATE;

                          /* Store the resource type so that we can
                             PROPFIND on this collection. */
                          comb->priv.restype = defn->restype;
                        }
                    }
                  else
                    {
                      /* e.g. "/root/!svn/activity" (we just know "act") */
                      return TRUE;
                    }

                  break;
                }
            }

          /* if completed the loop, then it is an unrecognized subdir */
          if (defn->name == NULL)
            return TRUE;
        }
    }
  else
    {
      /* Anything under the root, but not under "!svn". These are all
         version-controlled resources. */
      comb->res.type = DAV_RESOURCE_TYPE_REGULAR;
      comb->res.versioned = TRUE;

      /* The location of these resources corresponds directly to the URI,
         and we keep the leading "/". */
      comb->priv.repos_path = comb->priv.uri_path->data;
    }

  return FALSE;
}


static dav_error *
prep_regular(dav_resource_combined *comb)
{
  apr_pool_t *pool = comb->res.pool;
  dav_svn_repos *repos = comb->priv.repos;
  svn_error_t *serr;
  dav_error *derr;
  svn_node_kind_t kind;

  /* A REGULAR resource might have a specific revision already (e.g. if it
     is part of a baseline collection). However, if it doesn't, then we
     will assume that we need the youngest revision.
     ### other cases besides a BC? */
  if (comb->priv.root.rev == SVN_INVALID_REVNUM)
    {
      serr = dav_svn__get_youngest_rev(&comb->priv.root.rev, repos, pool);
      if (serr != NULL)
        {
          return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                      "Could not determine the proper "
                                      "revision to access",
                                      pool);
        }
    }
  else
    {
      /* Did we have a query for this REGULAR resource? */
      if (comb->priv.r->parsed_uri.query)
        {
          /* If yes, it's 'idempotent' only if peg revision is specified. */
          comb->priv.idempotent = comb->priv.pegged;
        }
      else
        {
          /* Otherwise, we have the specific revision in URI, so the resource
             is 'idempotent'. */
          comb->priv.idempotent = TRUE;
        }
    }

  /* get the root of the tree */
  serr = svn_fs_revision_root(&comb->priv.root.root, repos->fs,
                              comb->priv.root.rev, pool);
  if (serr != NULL)
    {
      return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                  "Could not open the root of the "
                                  "repository",
                                  pool);
    }

  derr = fs_check_path(&kind, comb->priv.root.root,
                       comb->priv.repos_path, pool);
  if (derr != NULL)
    return derr;

  comb->res.exists = (kind != svn_node_none);
  comb->res.collection = (kind == svn_node_dir);

  /* HACK:  dav_get_resource_state() is making shortcut assumptions
     about how to distinguish a null resource from a lock-null
     resource.  This is the only way to get around that problem.
     Without it, it won't ever detect lock-nulls, and thus 'svn unlock
     nonexistentURL' will always return 404's. */
  if (! comb->res.exists)
    comb->priv.r->path_info = (char *) "";

  return NULL;
}


static dav_error *
prep_version(dav_resource_combined *comb)
{
  svn_error_t *serr;
  apr_pool_t *pool = comb->res.pool;

  /* we are accessing the Version Resource by REV/PATH */

  /* ### assert: .baselined = TRUE */

  /* if we don't have a revision, then assume the youngest */
  if (!SVN_IS_VALID_REVNUM(comb->priv.root.rev))
    {
      serr = dav_svn__get_youngest_rev(&comb->priv.root.rev,
                                       comb->priv.repos,
                                       pool);
      if (serr != NULL)
        {
          /* ### might not be a baseline */

          return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                      "Could not fetch 'youngest' revision "
                                      "to enable accessing the latest "
                                      "baseline resource.",
                                      pool);
        }
    }

  /* ### baselines have no repos_path, and we don't need to open
     ### a root (yet). we just needed to ensure that we have the proper
     ### revision number. */

  if (!comb->priv.root.root)
    {
      serr = svn_fs_revision_root(&comb->priv.root.root,
                                  comb->priv.repos->fs,
                                  comb->priv.root.rev,
                                  pool);
      if (serr != NULL)
        {
          return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                      "Could not open a revision root.",
                                      pool);
        }
    }

  /* ### we should probably check that the revision is valid */
  comb->res.exists = TRUE;

  /* Set up the proper URI. Most likely, we arrived here via a VCC,
     so the URI will be incorrect. Set the canonical form. */
  /* ### assuming a baseline */
  comb->res.uri = dav_svn__build_uri(comb->priv.repos,
                                     DAV_SVN__BUILD_URI_BASELINE,
                                     comb->priv.root.rev, NULL,
                                     FALSE /* add_href */,
                                     pool);

  return NULL;
}


static dav_error *
prep_history(dav_resource_combined *comb)
{
  return NULL;
}


static dav_error *
prep_working(dav_resource_combined *comb)
{
  apr_pool_t *pool = comb->res.pool;
  svn_error_t *serr;
  dav_error *derr;
  svn_node_kind_t kind;
  const char *txn_name = comb->priv.root.txn_name;

  /* A txnroot object will already have the txn_name filled in, but a
     DeltaV 'working resource' will only have the activity_id at this
     point. */
  if (txn_name == NULL)
    {
      if (!comb->priv.root.activity_id)
        return dav_svn__new_error(comb->res.pool, HTTP_BAD_REQUEST, 0, 0,
                                  "The request did not specify an activity ID");

      txn_name = dav_svn__get_txn(comb->priv.repos,
                                  comb->priv.root.activity_id);
      if (txn_name == NULL)
        {
          return dav_svn__new_error(pool, HTTP_BAD_REQUEST, 0, 0,
                                    "An unknown activity was specified in the "
                                    "URL. This is generally caused by a "
                                    "problem in the client software.");
        }
      comb->priv.root.txn_name = txn_name;
    }

  /* get the FS transaction, given its name */
  serr = svn_fs_open_txn(&comb->priv.root.txn, comb->priv.repos->fs, txn_name,
                         pool);
  if (serr != NULL)
    {
      if (serr->apr_err == SVN_ERR_FS_NO_SUCH_TRANSACTION)
        {
          svn_error_clear(serr);
          return dav_svn__new_error(pool, HTTP_INTERNAL_SERVER_ERROR, 0, 0,
                                    "An activity was specified and found, but "
                                    "the corresponding SVN FS transaction was "
                                    "not found.");
        }
      return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                  "Could not open the SVN FS transaction "
                                  "corresponding to the specified activity.",
                                  pool);
    }

  if (comb->res.baselined)
    {
      /* a Working Baseline */

      /* if the transaction exists, then the working resource exists */
      comb->res.exists = TRUE;

      return NULL;
    }

  /* Set the txn author if not previously set.  Protect against multi-author
   * commits by verifying authenticated user associated with the current
   * request is the same as the txn author.
   * Note that anonymous requests are being excluded as being a change
   * in author, because the commit may touch areas of the repository
   * that are anonymous writeable as well as areas that are not.
   */
  if (comb->priv.repos->username)
    {
      svn_string_t *current_author;
      svn_string_t request_author;

      serr = svn_fs_txn_prop(&current_author, comb->priv.root.txn,
                             SVN_PROP_REVISION_AUTHOR, pool);
      if (serr != NULL)
        {
          return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                   "Failed to retrieve author of the SVN FS transaction "
                   "corresponding to the specified activity.",
                   pool);
        }

      request_author.data = comb->priv.repos->username;
      request_author.len = strlen(request_author.data);
      if (!current_author)
        {
          serr = svn_fs_change_txn_prop(comb->priv.root.txn,
                                        SVN_PROP_REVISION_AUTHOR,
                                        &request_author, pool);
          if (serr != NULL)
            {
              return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                       "Failed to set the author of the SVN FS transaction "
                       "corresponding to the specified activity.",
                       pool);
            }
        }
      else if (!svn_string_compare(current_author, &request_author))
        {
          return dav_svn__new_error(pool, HTTP_NOT_IMPLEMENTED, 0, 0,
                                    "Multi-author commits not supported.");
        }
    }

  /* get the root of the tree */
  serr = svn_fs_txn_root(&comb->priv.root.root, comb->priv.root.txn, pool);
  if (serr != NULL)
    {
      return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                  "Could not open the (transaction) root of "
                                  "the repository",
                                  pool);
    }

  derr = fs_check_path(&kind, comb->priv.root.root,
                       comb->priv.repos_path, pool);
  if (derr != NULL)
    return derr;

  comb->res.exists = (kind != svn_node_none);
  comb->res.collection = (kind == svn_node_dir);

  if (comb->res.exists
      && comb->priv.r->method_number == M_MKCOL
      && comb->priv.repos->is_svn_client)
    {
      /* mod_dav will now continue returning a generic HTTP_METHOD_NOT_ALLOWED
         error, which doesn't produce nice output on SVN, nor gives any details
         on why the operation failed.

         Let's error out a bit earlier and produce an error message that is
         easier to understand for both clients and users. */

      /* It would be nice if we could error out a bit later (see issue #2295),
         like in create_collection(), but mod_dav outsmarts us by just
         returning the error when the node exists. */

      return dav_svn__convert_err(
                  svn_error_createf(SVN_ERR_FS_ALREADY_EXISTS, NULL,
                                    "Path already exists, path '%s'",
                                    comb->priv.repos_path),
                  HTTP_METHOD_NOT_ALLOWED, NULL, pool);
    }

  return NULL;
}


static dav_error *
prep_activity(dav_resource_combined *comb)
{
  const char *txn_name;

  if (!comb->priv.root.activity_id)
    return dav_svn__new_error(comb->res.pool, HTTP_BAD_REQUEST, 0, 0,
                              "The request did not specify an activity ID");

  txn_name = dav_svn__get_txn(comb->priv.repos, comb->priv.root.activity_id);

  comb->priv.root.txn_name = txn_name;
  comb->res.exists = txn_name != NULL;

  return NULL;
}


static dav_error *
prep_private(dav_resource_combined *comb)
{
  svn_error_t *serr;
  apr_pool_t *pool = comb->res.pool;

  if (comb->priv.restype == DAV_SVN_RESTYPE_VCC)
    {
      /* ### what to do */
    }
  else if (comb->priv.restype == DAV_SVN_RESTYPE_TXN_COLLECTION)
    {
      /* Open the named transaction. */

      if (comb->priv.root.txn_name == NULL)
        return dav_svn__new_error(pool, HTTP_BAD_REQUEST, 0, 0,
                                  "An unknown txn name was specified in the "
                                  "URL.");

      serr = svn_fs_open_txn(&comb->priv.root.txn,
                             comb->priv.repos->fs,
                             comb->priv.root.txn_name, pool);
      if (serr != NULL)
        {
          if (serr->apr_err == SVN_ERR_FS_NO_SUCH_TRANSACTION)
            {
              svn_error_clear(serr);
              comb->res.exists = FALSE;
              return dav_svn__new_error(pool, HTTP_NOT_FOUND, 0, 0,
                                        "Named transaction doesn't exist.");
            }
          return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                      "Could not open specified transaction.",
                                      pool);
        }
      comb->res.exists = TRUE;
    }

  return NULL;
}


static const struct res_type_handler
{
  dav_resource_type type;
  dav_error * (*prep)(dav_resource_combined *comb);

} res_type_handlers[] =
{
  /* skip UNKNOWN */
  { DAV_RESOURCE_TYPE_REGULAR, prep_regular },
  { DAV_RESOURCE_TYPE_VERSION, prep_version },
  { DAV_RESOURCE_TYPE_HISTORY, prep_history },
  { DAV_RESOURCE_TYPE_WORKING, prep_working },
  /* skip WORKSPACE */
  { DAV_RESOURCE_TYPE_ACTIVITY, prep_activity },
  { DAV_RESOURCE_TYPE_PRIVATE, prep_private },

  { 0, NULL }   /* sentinel */
};


/*
** ### docco...
**
** Set .exists and .collection
** open other, internal bits...
*/
static dav_error *
prep_resource(dav_resource_combined *comb)
{
  const struct res_type_handler *scan;

  for (scan = res_type_handlers; scan->prep != NULL; ++scan)
    {
      if (comb->res.type == scan->type)
        return (*scan->prep)(comb);
    }

  return dav_svn__new_error(comb->res.pool, HTTP_INTERNAL_SERVER_ERROR, 0, 0,
                            "DESIGN FAILURE: unknown resource type");
}


static dav_resource *
create_private_resource(const dav_resource *base,
                        enum dav_svn_private_restype restype)
{
  dav_resource_combined *comb;
  svn_stringbuf_t *path;
  const struct special_defn *defn;

  for (defn = special_subdirs; defn->name != NULL; ++defn)
    if (defn->restype == restype)
      break;
  /* assert: defn->name != NULL */

  path = svn_stringbuf_createf(base->pool, "/%s/%s",
                            base->info->repos->special_uri, defn->name);

  comb = apr_pcalloc(base->pool, sizeof(*comb));

  /* ### can/should we leverage prep_resource */

  comb->res.type = DAV_RESOURCE_TYPE_PRIVATE;

  comb->res.exists = TRUE;
  comb->res.collection = TRUE;                  /* ### always true? */
  /* versioned = baselined = working = FALSE */

  if (base->info->repos->root_path[1])
    comb->res.uri = apr_pstrcat(base->pool, base->info->repos->root_path,
                                path->data, SVN_VA_NULL);
  else
    comb->res.uri = path->data;
  comb->res.info = &comb->priv;
  comb->res.hooks = &dav_svn__hooks_repository;
  comb->res.pool = base->pool;

  comb->priv.uri_path = path;
  comb->priv.repos = base->info->repos;
  comb->priv.root.rev = SVN_INVALID_REVNUM;
  return &comb->res;
}


static void log_warning(void *baton, svn_error_t *err)
{
  request_rec *r = baton;
  const char *continuation = "";

  /* ### hmm. the FS is cleaned up at request cleanup time. "r" might
     ### not really be valid. we should probably put the FS into a
     ### subpool to ensure it gets cleaned before the request.

     ### is there a good way to create and use a subpool for all
     ### of our functions ... ??
  */

  /* Not showing file/line so no point in tracing */
  err = svn_error_purge_tracing(err);
  while (err)
    {
      ap_log_rerror(APLOG_MARK, APLOG_ERR, APR_EGENERAL, r, "%s%s",
                    continuation, err->message);
      continuation = "-";
      err = err->child;
    }
}


AP_MODULE_DECLARE(dav_error *)
dav_svn_split_uri2(request_rec *r,
                   const char *uri_to_split,
                   const char *root_path,
                   const char **cleaned_uri,
                   int *trailing_slash,
                   const char **repos_basename,
                   const char **relative_path,
                   const char **repos_path,
                   apr_pool_t *pool)
{
  apr_size_t len1;
  int had_slash;
  const char *fs_path;
  const char *fs_parent_path;
  const char *relative;
  char *uri;

  /* one of these is NULL, the other non-NULL. */
  fs_path = dav_svn__get_fs_path(r);
  fs_parent_path = dav_svn__get_fs_parent_path(r);

  if ((fs_path == NULL) && (fs_parent_path == NULL))
    {
      /* ### are SVN_ERR_APMOD codes within the right numeric space? */
      return dav_svn__new_error(pool, HTTP_INTERNAL_SERVER_ERROR,
                                SVN_ERR_APMOD_MISSING_PATH_TO_FS, 0,
                                "The server is misconfigured: "
                                "either an SVNPath or SVNParentPath "
                                "directive is required to specify the location "
                                "of this resource's repository.");
    }

  /* make a copy so that we can do some work on it */
  uri = apr_pstrdup(pool, uri_to_split);

  /* remove duplicate slashes, and make sure URI has no trailing '/' */
  ap_no2slash(uri);
  len1 = strlen(uri);
  had_slash = (len1 > 0 && uri[len1 - 1] == '/');
  if (len1 > 1 && had_slash)
    uri[len1 - 1] = '\0';

  if (had_slash)
    *trailing_slash = TRUE;
  else
    *trailing_slash = FALSE;

  /* return the first item.  */
  *cleaned_uri = apr_pstrdup(pool, uri);

  /* The URL space defined by the SVN provider is always a virtual
     space. Construct the path relative to the configured Location
     (root_path). So... the relative location is simply the URL used,
     skipping the root_path.

     Note: mod_dav has canonialized root_path. It will not have a trailing
     slash (unless it is "/").

     Note: given a URI of /something and a root of /some, then it is
           impossible to be here (and end up with "thing"). This is simply
           because we control /some and are dispatched to here for its
           URIs. We do not control /something, so we don't get here. Or,
           if we *do* control /something, then it is for THAT root.
  */
  relative = ap_stripprefix(uri, root_path);

  /* We want a leading slash on the path specified by <relative>. This
     will almost always be the case since root_path does not have a trailing
     slash. However, if the root is "/", then the slash will be removed
     from <relative>. Backing up a character will put the leading slash
     back.

     Watch out for the empty string! This can happen when URI == ROOT_PATH.
     We simply turn the path into "/" for this case. */
  if (*relative == '\0')
    relative = "/";
  else if (*relative != '/')
    --relative;
  /* ### need a better name... it isn't "relative" because of the leading
     ### slash. something about SVN-private-path */

  /* Depending on whether SVNPath or SVNParentPath was used, we need
     to compute 'relative' and 'repos_basename' differently.  */

  /* Normal case:  the SVNPath command was used to specify a
     particular repository.  */
  if (fs_path != NULL)
    {
      /* the repos_basename is the last component of root_path. */
      *repos_basename = svn_dirent_basename(root_path, pool);

      /* 'relative' is already correct for SVNPath; the root_path
         already contains the name of the repository, so relative is
         everything beyond that.  */
    }

  else
    {
      /* SVNParentPath was used instead: assume the first component of
         'relative' is the name of a repository. */
      const char *magic_component, *magic_end;

      /* A repository name is required here.
         Remember that 'relative' always starts with a "/". */
      if (relative[1] == '\0')
        {
          /* ### are SVN_ERR_APMOD codes within the right numeric space? */
          return dav_svn__new_error(pool, HTTP_FORBIDDEN,
                                    SVN_ERR_APMOD_MALFORMED_URI, 0,
                                    "The URI does not contain the name "
                                    "of a repository.");
        }

      magic_end = ap_strchr_c(relative + 1, '/');
      if (!magic_end)
        {
          /* ### Request was for parent directory with no trailing
             slash; we probably ought to just redirect to same with
             trailing slash appended. */
          magic_component = relative + 1;
          relative = "/";
        }
      else
        {
          magic_component = apr_pstrndup(pool, relative + 1,
                                         magic_end - relative - 1);
          relative = magic_end;
        }

      /* return answer */
      *repos_basename = magic_component;
    }

  /* We can return 'relative' at this point too. */
  *relative_path = apr_pstrdup(pool, relative);

  /* Code to remove the !svn junk from the front of the relative path,
     mainly stolen from parse_uri().  This code assumes that
     the 'relative' string being parsed doesn't start with '/'. */
  relative++;

  {
    const char *special_uri = dav_svn__get_special_uri(r);
    apr_size_t len2;
    char ch;

    len1 = strlen(relative);
    len2 = strlen(special_uri);
    if (len1 > len2
        && ((ch = relative[len2]) == '/' || ch == '\0')
        && memcmp(relative, special_uri, len2) == 0)
      {
        if (ch == '\0')
          {
            /* relative is just "!svn", which is malformed. */
            return dav_svn__new_error(pool, HTTP_NOT_FOUND,
                                      SVN_ERR_APMOD_MALFORMED_URI, 0,
                                      "Nothing follows the svn special_uri.");
          }
        else
          {
            const struct special_defn *defn;

            /* skip past the "!svn/" prefix */
            relative += len2 + 1;
            len1 -= len2 + 1;

            for (defn = special_subdirs ; defn->name != NULL; ++defn)
              {
                apr_size_t len3 = strlen(defn->name);

                if (len1 >= len3 && memcmp(relative, defn->name, len3) == 0)
                  {
                    /* Found a matching special dir. */

                    if (relative[len3] == '\0')
                      {
                        /* relative is "!svn/xxx"  */
                        if (defn->numcomponents == 0)
                          *repos_path = NULL;
                        else
                          return dav_svn__new_error(
                                     pool, HTTP_NOT_FOUND,
                                     SVN_ERR_APMOD_MALFORMED_URI, 0,
                                     "Missing info after special_uri.");
                      }
                    else if (relative[len3] == '/')
                      {
                        /* Skip past defn->numcomponents components,
                           return everything beyond that.*/
                        int j;
                        const char *end = NULL, *start = relative + len3 + 1;

                        for (j = 0; j < defn->numcomponents; j++)
                          {
                            end = ap_strchr_c(start, '/');
                            if (! end)
                              break;
                            start = end + 1;
                          }

                        if (! end)
                          {
                            /* Did we break from the loop prematurely? */
                            if (j != (defn->numcomponents - 1))
                              return dav_svn__new_error(
                                         pool, HTTP_NOT_FOUND,
                                         SVN_ERR_APMOD_MALFORMED_URI, 0,
                                         "Not enough components after "
                                         "special_uri.");

                            if (! defn->has_repos_path)
                              /* It's okay to not have found a slash. */
                              *repos_path = NULL;
                            else
                              *repos_path = "/";
                          }
                        else
                          {
                            /* Found a slash after the special components. */
                            *repos_path = apr_pstrdup(pool, start - 1);
                          }
                      }
                    else
                      {
                        return
                          dav_svn__new_error(pool, HTTP_NOT_FOUND,
                                        SVN_ERR_APMOD_MALFORMED_URI, 0,
                                        "Unknown data after special_uri.");
                      }

                  break;
                  }
              }

            if (defn->name == NULL)
              return
                dav_svn__new_error(pool, HTTP_NOT_FOUND,
                                   SVN_ERR_APMOD_MALFORMED_URI, 0,
                                   "Couldn't match subdir after special_uri.");
          }
      }
    else
      {
        /* There's no "!svn/" at all, so the relative path is already
           a valid path within the repository.  */
        *repos_path = apr_pstrdup(pool, relative - 1);
      }
  }

  return NULL;
}

AP_MODULE_DECLARE(dav_error *)
dav_svn_split_uri(request_rec *r,
                  const char *uri_to_split,
                  const char *root_path,
                  const char **cleaned_uri,
                  int *trailing_slash,
                  const char **repos_basename,
                  const char **relative_path,
                  const char **repos_path)
{
  return dav_svn_split_uri2(r, uri_to_split, root_path, cleaned_uri,
                            trailing_slash, repos_basename, relative_path,
                            repos_path, r->pool);
}

/* Context for cleanup handler. */
struct cleanup_fs_access_baton
{
  svn_fs_t *fs;
  apr_pool_t *pool;
};


/* Pool cleanup handler.  Make sure fs's access ctx points to NULL
   when request pool is destroyed. */
static apr_status_t
cleanup_fs_access(void *data)
{
  svn_error_t *serr;
  struct cleanup_fs_access_baton *baton = data;

  serr = svn_fs_set_access(baton->fs, NULL);
  if (serr)
    {
      ap_log_perror(APLOG_MARK, APLOG_ERR, serr->apr_err, baton->pool,
                    "cleanup_fs_access: error clearing fs access context");
      svn_error_clear(serr);
    }

  return APR_SUCCESS;
}


/* Helper func to construct a special 'parentpath' private resource. */
static dav_error *
get_parentpath_resource(request_rec *r,
                        dav_resource **resource)
{
  const char *new_uri;
  dav_svn_root *droot = apr_pcalloc(r->pool, sizeof(*droot));
  dav_svn_repos *repos = apr_pcalloc(r->pool, sizeof(*repos));
  dav_resource_combined *comb = apr_pcalloc(r->pool, sizeof(*comb));
  apr_size_t len = strlen(r->uri);

  comb->res.exists = TRUE;
  comb->res.collection = TRUE;
  comb->res.uri = apr_pstrdup(r->pool, r->uri);
  comb->res.info = &comb->priv;
  comb->res.hooks = &dav_svn__hooks_repository;
  comb->res.pool = r->pool;
  comb->res.type = DAV_RESOURCE_TYPE_PRIVATE;

  comb->priv.restype = DAV_SVN_RESTYPE_PARENTPATH_COLLECTION;
  comb->priv.r = r;
  comb->priv.repos_path = "Collection of Repositories";
  comb->priv.root = *droot;
  droot->rev = SVN_INVALID_REVNUM;

  comb->priv.repos = repos;
  repos->pool = r->pool;
  repos->xslt_uri = dav_svn__get_xslt_uri(r);
  repos->autoversioning = dav_svn__get_autoversioning_flag(r);
  repos->bulk_updates = dav_svn__get_bulk_updates_flag(r);
  repos->v2_protocol = dav_svn__check_httpv2_support(r);
  repos->base_url = ap_construct_url(r->pool, "", r);
  repos->special_uri = dav_svn__get_special_uri(r);
  repos->username = r->user;
  repos->client_capabilities = apr_hash_make(repos->pool);
  repos->youngest_rev = SVN_INVALID_REVNUM;

  /* Make sure this type of resource always has a trailing slash; if
     not, redirect to a URI that does. */
  if (r->uri[len-1] != '/')
    {
      new_uri = apr_pstrcat(r->pool, ap_escape_uri(r->pool, r->uri),
                            "/", SVN_VA_NULL);
      apr_table_setn(r->headers_out, "Location",
                     ap_construct_url(r->pool, new_uri, r));
      return dav_svn__new_error(r->pool, HTTP_MOVED_PERMANENTLY, 0, 0,
                                "Requests for a collection must have a "
                                "trailing slash on the URI.");
    }

  /* No other "prepping" of resource needs to happen -- no opening
     of a repository or anything like that, because, well, there's
     no repository to open. */
  *resource = &comb->res;
  return NULL;
}

/* --------------- Borrowed from httpd's mod_negotiation.c -------------- */

typedef struct accept_rec {
  char *name;                 /* MUST be lowercase */
  float quality;
} accept_rec;

/*
 * Get a single Accept-encoding line from ACCEPT_LINE, and place the
 * information we have parsed out of it into RESULT.
 */

static const char *get_entry(apr_pool_t *p, accept_rec *result,
                             const char *accept_line)
{
    result->quality = 1.0f;

    /*
     * Note that this handles what I gather is the "old format",
     *
     *    Accept: text/html text/plain moo/zot
     *
     * without any compatibility kludges --- if the token after the
     * MIME type begins with a semicolon, we know we're looking at parms,
     * otherwise, we know we aren't.  (So why all the pissing and moaning
     * in the CERN server code?  I must be missing something).
     */

    result->name = ap_get_token(p, &accept_line, 0);
    ap_str_tolower(result->name);     /* You want case insensitive,
                                       * you'll *get* case insensitive.
                                       */

    while (*accept_line == ';')
      {
        /* Parameters ... */

        char *parm;
        char *cp;
        char *end;

        ++accept_line;
        parm = ap_get_token(p, &accept_line, 1);

        /* Look for 'var = value' --- and make sure the var is in lcase. */

        for (cp = parm; (*cp && !svn_ctype_isspace(*cp) && *cp != '='); ++cp)
          {
            *cp = (char)apr_tolower(*cp);
          }

        if (!*cp)
          {
            continue;           /* No '='; just ignore it. */
          }

        *cp++ = '\0';           /* Delimit var */
        while (*cp && (svn_ctype_isspace(*cp) || *cp == '='))
          {
            ++cp;
          }

        if (*cp == '"')
          {
            ++cp;
            for (end = cp;
                 (*end && *end != '\n' && *end != '\r' && *end != '\"');
                 end++);
          }
        else
          {
            for (end = cp; (*end && !svn_ctype_isspace(*end)); end++);
          }
        if (*end)
          {
            *end = '\0';        /* strip ending quote or return */
          }
        ap_str_tolower(cp);

        if (parm[0] == 'q'
            && (parm[1] == '\0' || (parm[1] == 's' && parm[2] == '\0')))
          {
            result->quality = (float) atof(cp);
          }
      }

    if (*accept_line == ',')
      {
        ++accept_line;
      }

    return accept_line;
}

/* @a accept_line is the Accept-Encoding header, which is of the
   format:

     Accept-Encoding: name; q=N;

   This function will return an array of accept_rec structures that
   contain the accepted encodings and the quality each one has
   associated with them.
*/
static apr_array_header_t *do_header_line(apr_pool_t *p,
                                          const char *accept_line)
{
    apr_array_header_t *accept_recs;

    if (!accept_line)
      return NULL;

    accept_recs = apr_array_make(p, 10, sizeof(accept_rec));

    while (*accept_line)
      {
        accept_rec *prefs = (accept_rec *) apr_array_push(accept_recs);
        accept_line = get_entry(p, prefs, accept_line);
      }

    return accept_recs;
}

/* ---------------------------------------------------------------------- */


/* qsort comparison function for the quality field of the accept_rec
   structure */
static int sort_encoding_pref(const void *accept_rec1, const void *accept_rec2)
{
  float diff = ((const accept_rec *) accept_rec1)->quality -
      ((const accept_rec *) accept_rec2)->quality;
  return (diff == 0 ? 0 : (diff > 0 ? -1 : 1));
}

static int get_svndiff_version(const struct accept_rec *rec)
{
  if (strcmp(rec->name, "svndiff2") == 0)
    return 2;
  else if (strcmp(rec->name, "svndiff1") == 0)
    return 1;
  else if (strcmp(rec->name, "svndiff") == 0)
    return 0;
  else
    return -1;
}

/* Parse and handle any possible Accept-Encoding header that has been
   sent as part of the request.  */
static void
negotiate_encoding_prefs(request_rec *r, int *svndiff_version)
{
  /* It would be nice if mod_negotiation
     <http://httpd.apache.org/docs-2.1/mod/mod_negotiation.html> could
     handle the Accept-Encoding header parsing for us.  Sadly, it
     looks like its data structures and routines are private (see
     httpd/modules/mappers/mod_negotiation.c).  Thus, we duplicate the
     necessary ones in this file. */
  int i;
  apr_array_header_t *encoding_prefs;
  apr_array_header_t *svndiff_encodings;
  svn_boolean_t accepts_svndiff2 = FALSE;

  encoding_prefs = do_header_line(r->pool,
                                  apr_table_get(r->headers_in,
                                                "Accept-Encoding"));

  if (!encoding_prefs || apr_is_empty_array(encoding_prefs))
    {
      *svndiff_version = 0;
      return;
    }

  svndiff_encodings = apr_array_make(r->pool, 3, sizeof(struct accept_rec));
  for (i = 0; i < encoding_prefs->nelts; i++)
    {
      const struct accept_rec *rec = &APR_ARRAY_IDX(encoding_prefs, i,
                                                    struct accept_rec);
      int version = get_svndiff_version(rec);

      if (version > 0)
        APR_ARRAY_PUSH(svndiff_encodings, struct accept_rec) = *rec;

      if (version == 2)
        accepts_svndiff2 = TRUE;
    }

  if (dav_svn__get_compression_level(r) == 0)
    {
      /* If the compression is disabled on the server, use the uncompressed
       * svndiff0 format, which we assume is always supported. */
      *svndiff_version = 0;
    }
  else if (accepts_svndiff2 && dav_svn__get_compression_level(r) == 1)
    {
      /* Enable svndiff2 if the client can read it, and if the server-side
       * compression level is set to 1.  Svndiff2 offers better speed and
       * compression ratio comparable to svndiff1 with compression level 1,
       * but not with other compression levels.
       */
      *svndiff_version = 2;
    }
  else if (svndiff_encodings->nelts > 0)
    {
      const struct accept_rec *rec;

      /* Otherwise, use what the client prefers to see. */
      svn_sort__array(svndiff_encodings, sort_encoding_pref);
      rec = &APR_ARRAY_IDX(svndiff_encodings, 0, struct accept_rec);
      *svndiff_version = get_svndiff_version(rec);
    }
  else
    {
      *svndiff_version = 0;
    }
}


/* The only two possible values for a capability. */
static const char *capability_yes = "yes";
static const char *capability_no = "no";

/* Convert CAPABILITIES, a hash table mapping 'const char *' keys to
 * "yes" or "no" values, to a list of all keys whose value is "yes".
 * Return the list, allocated in POOL, and use POOL for all temporary
 * allocation.
 */
static apr_array_header_t *
capabilities_as_list(apr_hash_t *capabilities, apr_pool_t *pool)
{
  apr_array_header_t *list = apr_array_make(pool, apr_hash_count(capabilities),
                                            sizeof(char *));
  apr_hash_index_t *hi;

  for (hi = apr_hash_first(pool, capabilities); hi; hi = apr_hash_next(hi))
    {
      const void *key;
      void *val;
      apr_hash_this(hi, &key, NULL, &val);
      if (strcmp((const char *) val, "yes") == 0)
        APR_ARRAY_PUSH(list, const char *) = key;
    }

  return list;
}


/* Given a non-NULL QUERY string of the form "key1=val1&key2=val2&...",
 * parse the keys and values into an apr table.  Allocate the table in
 * POOL;  dup all keys and values into POOL as well.
 *
 * Note that repeating the same key will cause table overwrites
 * (e.g. "r=3&r=5"), and that a lack of value ("p=") is legal, but
 * equivalent to not specifying the key at all.
 */
static apr_table_t *
querystring_to_table(const char *query, apr_pool_t *pool)
{
  apr_table_t *table = apr_table_make(pool, 2);
  apr_array_header_t *array = svn_cstring_split(query, "&", TRUE, pool);
  int i;
  for (i = 0; i < array->nelts; i++)
    {
      char *keyval = APR_ARRAY_IDX(array, i, char *);
      char *equals = strchr(keyval, '=');
      if (equals != NULL)
        {
          *equals = '\0';
          apr_table_set(table, keyval, equals + 1);
        }
    }
  return table;
}


/* Helper for get_resource(), called after COMB is fully parsed and prepped. */
static dav_error *
do_out_of_date_check(dav_resource_combined *comb, request_rec *r)
{
  svn_revnum_t created_rev;
  svn_error_t *serr;

  /* Do we have an X-SVN-Version-Name header? */
  if (! SVN_IS_VALID_REVNUM(comb->priv.version_name))
    return NULL;

  /* Note: LOCK and DELETE handlers already notice the header and do
     their own out-of-dateness checks.  MKCOL, COPY, MOVE don't supply
     the header at all, nor do MKACTIVITY, POST, or MERGE. */
  if (! ((r->method_number == M_PUT)
         || (r->method_number == M_PROPPATCH)))
    return NULL;

  /* Do an out-of-dateness check. */
  if ((serr = svn_fs_node_created_rev(&created_rev, comb->priv.root.root,
                                      comb->priv.repos_path, r->pool)))
    return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                "Could not get created rev of "
                                "resource", r->pool);

  if (SVN_IS_VALID_REVNUM(created_rev))
    {
      if (comb->priv.version_name < created_rev)
        {
          serr = svn_error_createf(SVN_ERR_RA_OUT_OF_DATE, NULL,
                                   comb->res.collection
                                    ? "Directory '%s' is out of date"
                                    : (comb->res.exists
                                        ? "File '%s' is out of date"
                                        : "'%s' is out of date"),
                                   comb->priv.repos_path);
          return dav_svn__convert_err(serr, HTTP_CONFLICT,
                                      "Attempting to modify out-of-date resource.",
                                      r->pool);
        }
      else if (comb->priv.version_name > created_rev)
        {
          svn_revnum_t txn_base_rev;

          txn_base_rev = svn_fs_txn_base_revision(comb->res.info->root.txn);
          if (comb->priv.version_name > txn_base_rev)
            {
              serr = svn_error_createf(SVN_ERR_FS_NO_SUCH_REVISION, NULL,
                                       "No such revision %ld",
                                       comb->priv.version_name);

              return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                          "Unknown base revision",
                                          r->pool);
            }
        }
    }
  else if (comb->res.collection)
    {
      /* Issue #4480: With HTTPv2 we can receive the first change for a
         directory after it has been made mutable, because one of its
         descendants was changed before changing the directory.

         We have to check if whatever the node is in HEAD is equivalent
         to what it was in the provided BASE revision.

         If the node was copied, we would process it before its decendants
         and we already performed quite a few checks when making it mutable
         via its descendant, so what we should really check here is if the
         properties changed since the BASE version.

         ### I think svn_fs_node_relation() checks for more changes than we
             should check for here. Needs further review. But it looks like
             this check matches the checks in the libsvn_fs commit editor.

             For now I would say reporting out of date in a few too many
             cases is safer than not reporting out of date when we should.
       */
      svn_revnum_t txn_base_rev;
      svn_fs_root_t *txn_base_root;
      svn_fs_root_t *rev_root;
      svn_fs_node_relation_t node_relation;

      txn_base_rev = svn_fs_txn_base_revision(comb->res.info->root.txn);

      if (comb->priv.version_name == txn_base_rev)
        return NULL; /* Easy out: Nothing changed */

      serr = svn_fs_revision_root(&txn_base_root, comb->res.info->repos->fs,
                                  txn_base_rev, r->pool);

      if (serr != NULL)
        {
          return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                      "Could not open the transaction revision "
                                      "for verification against the base "
                                      "revision", r->pool);
        }

      serr = svn_fs_revision_root(&rev_root, comb->res.info->repos->fs,
                                  comb->priv.version_name, r->pool);

      if (serr != NULL)
        {
          svn_fs_close_root(txn_base_root);
          return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                      "Could not open the base revision "
                                      "for verification against the "
                                      "transaction revision", r->pool);
        }

      serr = svn_fs_node_relation(&node_relation, rev_root,
                                  comb->priv.repos_path,
                                  txn_base_root,
                                  comb->priv.repos_path,
                                  r->pool);

      svn_fs_close_root(rev_root);
      svn_fs_close_root(txn_base_root);

      if (serr != NULL)
        {
          /* ### correct HTTP error? */
          return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                      "Unable to fetch the node revision id "
                                      "of the version resource within the "
                                      "revision",
                                      r->pool);
        }

      if (node_relation != svn_fs_node_unchanged)
        {
          serr = svn_error_createf(SVN_ERR_RA_OUT_OF_DATE, NULL,
                                   "Directory '%s' is out of date",
                                   comb->priv.repos_path);
          return dav_svn__convert_err(serr, HTTP_CONFLICT,
                                      "Attempting to modify out-of-date resource.",
                                      r->pool);
        }
    }

  return NULL;
}


/* Helper for get_resource().
 *
 * Given a fully fleshed out COMB object which has already been parsed
 * via parse_uri(), parse the querystring in QUERY.
 *
 * Specifically, look for optional 'p=PEGREV' and 'r=WORKINGREV'
 * values in the querystring, and modify COMB so that prep_regular()
 * opens the correct revision and path.
 */
static dav_error *
parse_querystring(request_rec *r, const char *query,
                  dav_resource_combined *comb, apr_pool_t *pool)
{
  svn_error_t *serr;
  svn_revnum_t working_rev, peg_rev;
  apr_table_t *pairs = querystring_to_table(query, pool);
  const char *prevstr = apr_table_get(pairs, "p");
  const char *wrevstr;
  const char *keyword_subst;

  /* Will we be doing keyword substitution? */
  keyword_subst = apr_table_get(pairs, "kw");
  if (keyword_subst && (strcmp(keyword_subst, "1") == 0))
    comb->priv.keyword_subst = TRUE;

  if (prevstr)
    {
      while (*prevstr == 'r')
        prevstr++;
      peg_rev = SVN_STR_TO_REV(prevstr);
      if (!SVN_IS_VALID_REVNUM(peg_rev))
        return dav_svn__new_error(pool, HTTP_BAD_REQUEST, 0, 0,
                                  "invalid peg rev in query string");
    }
  else
    {
      /* No peg-rev?  Default to HEAD, just like the cmdline client. */
      serr = dav_svn__get_youngest_rev(&peg_rev, comb->priv.repos, pool);
      if (serr != NULL)
        return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                    "Couldn't fetch youngest rev.", pool);
    }

  wrevstr = apr_table_get(pairs, "r");
  if (wrevstr)
    {
      while (*wrevstr == 'r')
        wrevstr++;
      working_rev = SVN_STR_TO_REV(wrevstr);
      if (!SVN_IS_VALID_REVNUM(working_rev))
        return dav_svn__new_error(pool, HTTP_BAD_REQUEST, 0, 0,
                                  "invalid working rev in query string");
    }
  else
    {
      /* No working-rev?  Assume it's equal to the peg-rev, just
         like the cmdline client does. */
      working_rev = peg_rev;
    }

  /* If WORKING_REV is younger than PEG_REV, we have a problem.
     Our node-tracing algorithms can't handle that scenario, so we'll
     disallow it here. */
  if (working_rev > peg_rev)
    return dav_svn__new_error(pool, HTTP_BAD_REQUEST, 0, 0,
                              "working rev greater than peg rev.");

  /* If WORKING_REV and PEG_REV are equivalent, we want to return the
     resource at the revision.  Otherwise, WORKING_REV is older than
     PEG_REV, so we need to crawl back through the history of
     REPOS_PATH@PEG_REV until we hit WORKING_REV.  We'll then redirect
     the client to the new location/revision pair found by that crawl. */
  if (working_rev == peg_rev)
    {
      comb->priv.root.rev = peg_rev;

      /* Did we have a peg revision?  Remember this little fact (in
         case deliver() needs to know it). */
      if (prevstr)
        comb->priv.pegged = TRUE;
    }
  else
    {
      const char *newpath, *location;
      apr_hash_t *locations;
      apr_array_header_t *loc_revs = apr_array_make(pool, 1,
                                                    sizeof(svn_revnum_t));

      dav_svn__authz_read_baton *arb = apr_pcalloc(pool, sizeof(*arb));
      arb->r = comb->priv.r;
      arb->repos = comb->priv.repos;

      APR_ARRAY_PUSH(loc_revs, svn_revnum_t) = working_rev;
      if ((serr = svn_repos_trace_node_locations(comb->priv.repos->fs,
                                                 &locations,
                                                 comb->priv.repos_path,
                                                 peg_rev,
                                                 loc_revs,
                                                 dav_svn__authz_read_func(arb),
                                                 arb,
                                                 pool)))
        return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                    "Couldn't trace history.", pool);

      newpath = apr_hash_get(locations, &working_rev, sizeof(working_rev));
      if (! newpath)
        return dav_svn__new_error(pool, HTTP_NOT_FOUND, 0, 0,
                                  "path doesn't exist in that revision.");

      /* Redirect folks to a canonical, peg-revision-only location.
         If they used a peg revision in this request, we can use a
         permanent redirect.  If they didn't (peg-rev is HEAD), we can
         only use a temporary redirect.  In either case, preserve the
         "keyword_subst" state in the redirected location, too.  */
      location = ap_construct_url(r->pool,
                                  apr_psprintf(r->pool, "%s%s?p=%ld%s",
                                               (comb->priv.repos->root_path[1]
                                                ? comb->priv.repos->root_path
                                                : ""),
                                               newpath, working_rev,
                                               keyword_subst ? "&kw=1" : ""),
                                  r);
      apr_table_setn(r->headers_out, "Location", location);
      return dav_svn__new_error(r->pool,
                                prevstr ? HTTP_MOVED_PERMANENTLY
                                        : HTTP_MOVED_TEMPORARILY,
                                0, 0, "redirecting to canonical location");
    }

  return NULL;
}

static dav_error *
get_resource(request_rec *r,
             const char *root_path,
             const char *label,
             int use_checked_in,
             dav_resource **resource)
{
  const char *fs_path;
  const char *repo_name;
  const char *xslt_uri;
  const char *fs_parent_path;
  dav_resource_combined *comb;
  dav_svn_repos *repos;
  const char *cleaned_uri;
  const char *repo_basename;
  const char *relative;
  const char *repos_path;
  const char *repos_key;
  const char *version_name;
  svn_error_t *serr;
  dav_error *err;
  int had_slash;
  dav_locktoken_list *ltl;
  struct cleanup_fs_access_baton *cleanup_baton;
  void *userdata;
  apr_hash_t *fs_config;

  repo_name = dav_svn__get_repo_name(r);
  xslt_uri = dav_svn__get_xslt_uri(r);
  fs_parent_path = dav_svn__get_fs_parent_path(r);

  if (r->method_number == M_COPY)
    {
      /* Workaround for issue #4531: Avoid a depth-infinity walk on
         the copy source by overriding the Depth header here.
         mod_dav defaults to infinite depth if this header is not set
         which makes copies O(size of source) rather than the desired O(1).
         ### Should be fixed by an explicit provider API feature in mod_dav. */
      apr_table_setn(r->headers_in, "Depth", "0");
    }

  /* Special case: detect and build the SVNParentPath as a unique type
     of private resource, iff the SVNListParentPath directive is 'on'. */
  if (dav_svn__is_parentpath_list(r))
    {
      /* Only allow GET and HEAD on the parentpath resource
       * httpd uses the same method_number for HEAD as GET */
      if (r->method_number != M_GET)
        {
          int status;

          /* Marshall the error back to the client by generating by
           * way of the dav_svn__error_response_tag trick. */
          err = dav_svn__new_error(r->pool, HTTP_METHOD_NOT_ALLOWED,
                                   SVN_ERR_APMOD_MALFORMED_URI, 0,
                                   "The URI does not contain the name "
                                   "of a repository.");
          /* can't use r->allowed since the default handler isn't called */
          apr_table_setn(r->headers_out, "Allow", "GET,HEAD");
          status = dav_svn__error_response_tag(r, err);

          return dav_push_error(r->pool, status, err->error_id, NULL, err);
        }

      err = get_parentpath_resource(r, resource);
      if (err)
        return err;
      return NULL;
    }

  /* This does all the work of interpreting/splitting the request uri. */
  err = dav_svn_split_uri(r, r->uri, root_path,
                          &cleaned_uri, &had_slash,
                          &repo_basename, &relative, &repos_path);
  if (err)
    return err;

  /* The path that we will eventually try to open as an svn
     repository.  Normally defined by the SVNPath directive. */
  fs_path = dav_svn__get_fs_path(r);

  /* If the SVNParentPath directive was used instead... */
  if (fs_parent_path != NULL)
    {
      /* ...then the URL to the repository is actually one implicit
         component longer... */
      root_path = svn_urlpath__join(root_path, repo_basename, r->pool);
      /* ...and we need to specify exactly what repository to open. */
      fs_path = svn_dirent_join(fs_parent_path, repo_basename, r->pool);
    }

  /* Start building and filling a 'combination' object. */
  comb = apr_pcalloc(r->pool, sizeof(*comb));
  comb->res.info = &comb->priv;
  comb->res.hooks = &dav_svn__hooks_repository;
  comb->res.pool = r->pool;
  comb->res.uri = cleaned_uri;

  /* Original request, off which to generate subrequests later. */
  comb->priv.r = r;

  /* ### ugly hack to carry over Content-Type data to the open_stream, which
     ### does not have access to the request headers. */
  {
    const char *ct = apr_table_get(r->headers_in, "content-type");

    comb->priv.is_svndiff =
      ct != NULL
      && strcmp(ct, SVN_SVNDIFF_MIME_TYPE) == 0;
  }

  negotiate_encoding_prefs(r, &comb->priv.svndiff_version);

  /* ### and another hack for computing diffs to send to the client */
  comb->priv.delta_base = apr_table_get(r->headers_in,
                                        SVN_DAV_DELTA_BASE_HEADER);

  /* Gather any options requested by an svn client. */
  comb->priv.svn_client_options = apr_table_get(r->headers_in,
                                                SVN_DAV_OPTIONS_HEADER);

  /* See if the client sent a custom 'version name' request header. */
  version_name = apr_table_get(r->headers_in, SVN_DAV_VERSION_NAME_HEADER);
  comb->priv.version_name
    = version_name ? SVN_STR_TO_REV(version_name): SVN_INVALID_REVNUM;

  /* Remember checksums, if any. */
  comb->priv.base_checksum =
    apr_table_get(r->headers_in, SVN_DAV_BASE_FULLTEXT_MD5_HEADER);
  comb->priv.result_checksum =
    apr_table_get(r->headers_in, SVN_DAV_RESULT_FULLTEXT_MD5_HEADER);

  /* "relative" is part of the "uri" string, so it has the proper
     lifetime to store here. */
  /* ### that comment no longer applies. we're creating a string with its
     ### own lifetime now. so WHY are we using a string? hmm... */
  comb->priv.uri_path = svn_stringbuf_create(relative, r->pool);

  /* initialize this until we put something real here */
  comb->priv.root.rev = SVN_INVALID_REVNUM;

  /* create the repository structure and stash it away */
  repos = apr_pcalloc(r->pool, sizeof(*repos));
  repos->pool = r->pool;
  repos->youngest_rev = SVN_INVALID_REVNUM;

  comb->priv.repos = repos;

  /* We are assuming the root_path will live at least as long as this
     resource. Considering that it typically comes from the per-dir
     config in mod_dav, this is valid for now. */
  repos->root_path = svn_path_uri_encode(root_path, r->pool);

  /* where is the SVN FS for this resource? */
  repos->fs_path = fs_path;

  /* A name for the repository */
  repos->repo_name = repo_name;

  /* The repository filesystem basename */
  repos->repo_basename = repo_basename;

  /* An XSL transformation */
  repos->xslt_uri = xslt_uri;

  /* Is autoversioning active in this repos? */
  repos->autoversioning = dav_svn__get_autoversioning_flag(r);

  /* Are bulk updates allowed in this repos? */
  repos->bulk_updates = dav_svn__get_bulk_updates_flag(r);

  /* Are we advertising HTTP v2 protocol support? */
  repos->v2_protocol = dav_svn__check_httpv2_support(r);

  /* Path to activities database */
  repos->activities_db = dav_svn__get_activities_db(r);
  if (repos->activities_db == NULL)
    /* If not specified, use default ($repos/dav/activities.d). */
    repos->activities_db = svn_dirent_join(repos->fs_path,
                                         DEFAULT_ACTIVITY_DB,
                                         r->pool);
  else if (fs_parent_path != NULL)
    /* If this is a ParentPath-based repository, treat the specified
       path as a similar parent directory. */
    repos->activities_db = svn_dirent_join(repos->activities_db,
                                           svn_dirent_basename(repos->fs_path,
                                                               r->pool),
                                           r->pool);

  /* Remember various bits for later URL construction */
  repos->base_url = ap_construct_url(r->pool, "", r);
  repos->special_uri = dav_svn__get_special_uri(r);

  /* Remember who is making this request */
  repos->username = r->user;

  /* Allocate room for capabilities, but don't search for any until
     we know that this is a Subversion client. */
  repos->client_capabilities = apr_hash_make(repos->pool);

  /* Remember if the requesting client is a Subversion client, and if
     so, what its capabilities are. */
  {
    const char *val = apr_table_get(r->headers_in, "User-Agent");

    if (val && (ap_strstr_c(val, "SVN/") == val))
      {
        repos->is_svn_client = TRUE;

        /* Client capabilities are self-reported.  There is no
           guarantee the client actually has the capabilities it says
           it has, we just assume it is in the client's interests to
           report accurately.  Also, we only remember the capabilities
           the server cares about (even though the client may send
           more than that). */

        /* Start out assuming no capabilities. */
        svn_hash_sets(repos->client_capabilities,
                      SVN_RA_CAPABILITY_MERGEINFO,
                      capability_no);

        /* Then see what we can find. */
        val = apr_table_get(r->headers_in, "DAV");
        if (val)
          {
            apr_array_header_t *vals
              = svn_cstring_split(val, ",", TRUE, r->pool);

            if (svn_cstring_match_list(SVN_DAV_NS_DAV_SVN_MERGEINFO, vals))
              {
                svn_hash_sets(repos->client_capabilities,
                              SVN_RA_CAPABILITY_MERGEINFO, capability_yes);
              }
          }
      }
  }

  /* Retrieve/cache open repository */
  repos_key = apr_pstrcat(r->pool, "mod_dav_svn:", fs_path, SVN_VA_NULL);
  apr_pool_userdata_get(&userdata, repos_key, r->connection->pool);
  repos->repos = userdata;
  if (repos->repos == NULL)
    {
      const char *fs_type;

      /* construct FS configuration parameters */
      fs_config = apr_hash_make(r->connection->pool);
      svn_hash_sets(fs_config, SVN_FS_CONFIG_FSFS_CACHE_DELTAS,
                    dav_svn__get_txdelta_cache_flag(r) ? "1" :"0");
      svn_hash_sets(fs_config, SVN_FS_CONFIG_FSFS_CACHE_FULLTEXTS,
                    dav_svn__get_fulltext_cache_flag(r) ? "1" :"0");
      svn_hash_sets(fs_config, SVN_FS_CONFIG_FSFS_CACHE_REVPROPS,
                    dav_svn__get_revprop_cache_flag(r) ? "2" :"0");
      svn_hash_sets(fs_config, SVN_FS_CONFIG_FSFS_CACHE_NODEPROPS,
                    dav_svn__get_nodeprop_cache_flag(r) ? "1" :"0");
      svn_hash_sets(fs_config, SVN_FS_CONFIG_FSFS_BLOCK_READ,
                    dav_svn__get_block_read_flag(r) ? "1" :"0");

      /* Disallow BDB/event until issue 4157 is fixed. */
      if (!strcmp(ap_show_mpm(), "event"))
        {
          serr = svn_repos__fs_type(&fs_type, fs_path, r->connection->pool);
          if (serr)
            {
              /* svn_repos_open2 is going to fail, use that error. */
              svn_error_clear(serr);
              serr = NULL;
            }
          else if (!strcmp(fs_type, "bdb"))
            serr = svn_error_createf(SVN_ERR_UNSUPPORTED_FEATURE, NULL,
                                     "BDB repository at '%s' is not compatible "
                                     "with event MPM",
                                     fs_path);
        }
      else
        serr = NULL;

      /* open the FS */
      if (!serr)
        serr = svn_repos_open3(&(repos->repos), fs_path, fs_config,
                               r->connection->pool, r->pool);
      if (serr != NULL)
        {
          /* The error returned by svn_repos_open2 might contain the
             actual path to the failed repository.  We don't want to
             leak that path back to the client, because that would be
             a security risk, but we do want to log the real error on
             the server side. */

          apr_status_t cause = svn_error_root_cause(serr)->apr_err;
          if (APR_STATUS_IS_ENOENT(cause) || APR_STATUS_IS_ENOTDIR(cause))
            return dav_svn__sanitize_error(
                serr, "Could not find the requested SVN filesystem",
                HTTP_NOT_FOUND, r);
          else
            return dav_svn__sanitize_error(
                serr, "Could not open the requested SVN filesystem",
                HTTP_INTERNAL_SERVER_ERROR, r);
        }

      /* Cache the open repos for the next request on this connection */
      apr_pool_userdata_set(repos->repos, repos_key,
                            NULL, r->connection->pool);

      /* Store the capabilities of the current connection, making sure
         to use the same pool repos->repos itself was created in. */
      serr = svn_repos_remember_client_capabilities
        (repos->repos, capabilities_as_list(repos->client_capabilities,
                                            r->connection->pool));
      if (serr != NULL)
        {
          return dav_svn__sanitize_error(serr,
                                         "Error storing client capabilities "
                                         "in repos object",
                                         HTTP_INTERNAL_SERVER_ERROR, r);
        }

      /* Configure hook script environment variables. */
      serr = svn_repos_hooks_setenv(repos->repos, dav_svn__get_hooks_env(r),
                                    r->pool);
      if (serr)
        return dav_svn__sanitize_error(serr,
                                       "Error settings hooks environment",
                                       HTTP_INTERNAL_SERVER_ERROR, r);
    }

  /* cache the filesystem object */
  repos->fs = svn_repos_fs(repos->repos);

  /* capture warnings during cleanup of the FS */
  svn_fs_set_warning_func(repos->fs, log_warning, r);

  /* if an authenticated username is present, attach it to the FS */
  if (r->user)
    {
      svn_fs_access_t *access_ctx;

      /* The fs is cached in connection->pool, but the fs access
         context lives in r->pool.  Because the username or token
         could change on each request, we need to make sure that the
         fs points to a NULL access context after the request is gone. */
      cleanup_baton = apr_pcalloc(r->pool, sizeof(*cleanup_baton));
      cleanup_baton->pool = r->pool;
      cleanup_baton->fs = repos->fs;
      apr_pool_cleanup_register(r->pool, cleanup_baton, cleanup_fs_access,
                                apr_pool_cleanup_null);

      /* Create an access context based on the authenticated username. */
      serr = svn_fs_create_access(&access_ctx, r->user, r->pool);
      if (serr)
        {
          return dav_svn__sanitize_error(serr,
                                         "Could not create fs access context",
                                         HTTP_INTERNAL_SERVER_ERROR, r);
        }

      /* Attach the access context to the fs. */
      serr = svn_fs_set_access(repos->fs, access_ctx);
      if (serr)
        {
          return dav_svn__sanitize_error(serr, "Could not attach access "
                                         "context to fs",
                                         HTTP_INTERNAL_SERVER_ERROR, r);
        }
    }

  /* Look for locktokens in the "If:" request header. */
  err = dav_get_locktoken_list(r, &ltl);

  /* dav_get_locktoken_list claims to return a NULL list when no
     locktokens are present.  But it actually throws this error
     instead!  So we're deliberately trapping/ignoring it.

     This is a workaround for a bug in mod_dav.  Remove this when the
     bug is fixed in mod_dav.  See Subversion Issue #2248 */
  if (err && (err->error_id != DAV_ERR_IF_ABSENT))
    return err;

  /* If one or more locktokens are present in the header, push them
     into the filesystem access context. */
  if (ltl)
    {
      svn_fs_access_t *access_ctx;
      dav_locktoken_list *list = ltl;

      serr = svn_fs_get_access(&access_ctx, repos->fs);
      if (serr || !access_ctx)
        {
          if (serr == NULL)
            serr = svn_error_create(SVN_ERR_FS_LOCK_OWNER_MISMATCH, NULL, NULL);
          return dav_svn__sanitize_error(serr, "Lock token is in request, "
                                         "but no user name",
                                         HTTP_BAD_REQUEST, r);
        }

      do {
        /* Note the path/lock pairs are only for lock token checking
           in access, and the relative path is not actually accurate
           as it contains the !svn bits.  However, we're using only
           the tokens anyway (for access control). */

        serr = svn_fs_access_add_lock_token2(access_ctx, relative,
                                             list->locktoken->uuid_str);

        if (serr)
          return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                      "Error pushing token into filesystem.",
                                      r->pool);
        list = list->next;

      } while (list);
    }


  /* Figure out the type of the resource. Note that we have a PARSE step
     which is separate from a PREP step. This is because the PARSE can
     map multiple URLs to the same resource type. The PREP operates on
     the type of the resource. */

  /* skip over the leading "/" in the relative URI */
  if (parse_uri(comb, relative + 1, label, use_checked_in))
    goto malformed_URI;

  /* Check for a query string on a regular-type resource; this allows
     us to discover and parse  a "universal" rev-path URI of the form
     "path?[r=REV][&p=PEGREV]" */
  if ((comb->res.type == DAV_RESOURCE_TYPE_REGULAR)
      && (r->parsed_uri.query != NULL)
      && ((err = parse_querystring(r, r->parsed_uri.query, comb, r->pool))))
    return err;

#ifdef SVN_DEBUG
  if (comb->res.type == DAV_RESOURCE_TYPE_UNKNOWN)
    {
      /* Unknown URI. Return NULL to indicate "no resource" */
      DBG0("DESIGN FAILURE: should not be UNKNOWN at this point");
      *resource = NULL;
      return NULL;
    }
#endif

  /* prepare the resource for operation */
  if ((err = prep_resource(comb)) != NULL)
    return err;

  /* a GET request for a REGULAR collection resource MUST have a trailing
     slash. Redirect to include one if it does not. */
  if (comb->res.collection && comb->res.type == DAV_RESOURCE_TYPE_REGULAR
      && !had_slash && r->method_number == M_GET)
    {
      const char *new_path = apr_pstrcat(r->pool,
                                         ap_escape_uri(r->pool, r->uri),
                                         "/",
                                         r->args ? "?" : "",
                                         r->args ? r->args : "",
                                         SVN_VA_NULL);
      apr_table_setn(r->headers_out, "Location",
                     ap_construct_url(r->pool, new_path, r));
      return dav_svn__new_error(r->pool, HTTP_MOVED_PERMANENTLY, 0, 0,
                                "Requests for a collection must have a "
                                "trailing slash on the URI.");
    }

  /* HTTPv2: for write-requests, out-of-dateness checks happen via
     Base-Version header rather via CHECKOUT requests.

     If a Base-Version header is present on a write request, we need
     to do the out-of-dateness check *here*, rather than in other
     dav-provider vtable funcs.  That's because a number of mod_dav
     methods annoyingly trap and genericize our error messages.  */
  if ((err = do_out_of_date_check(comb, r)) != NULL)
    return err;

  *resource = &comb->res;
  return NULL;

 malformed_URI:
  /* A malformed URI error occurs when a URI indicates the "special" area,
     yet it has an improper construction. Generally, this is because some
     doofus typed it in manually or has a buggy client. */
  /* ### pick something other than HTTP_INTERNAL_SERVER_ERROR */
  /* ### are SVN_ERR_APMOD codes within the right numeric space? */
  return dav_svn__new_error(r->pool, HTTP_INTERNAL_SERVER_ERROR,
                            SVN_ERR_APMOD_MALFORMED_URI, 0,
                            "The URI indicated a resource within Subversion's "
                            "special resource area, but does not exist. This "
                            "is generally caused by a problem in the client "
                            "software.");
}


/* Helper func:  return the parent of PATH, allocated in POOL.  If
   IS_URLPATH is set, PATH is a urlpath; otherwise, it's either a
   relpath or an fspath. */
static const char *
get_parent_path(const char *path,
                svn_boolean_t is_urlpath,
                apr_pool_t *pool)
{
  if (*path != '\0') /* not an empty string */
    {
      if (is_urlpath)
        return svn_urlpath__dirname(path, pool);
      else
        return svn_fspath__dirname(path, pool);
    }

  return path;
}


static dav_error *
get_parent_resource(const dav_resource *resource,
                    dav_resource **parent_resource)
{
  dav_resource *parent;
  dav_resource_private *parentinfo;
  svn_stringbuf_t *path = resource->info->uri_path;

  /* Initialize the return value. */
  *parent_resource = NULL;

  /* The root of the repository has no parent. */
  if (path->len == 1 && *path->data == '/')
    return NULL;

  /* If possible, create a parent based on the type of RESOURCE. */
  switch (resource->type)
    {
    case DAV_RESOURCE_TYPE_REGULAR:

      parent = apr_pcalloc(resource->pool, sizeof(*parent));
      parentinfo  = apr_pcalloc(resource->pool, sizeof(*parentinfo));

      parent->type = DAV_RESOURCE_TYPE_REGULAR;
      parent->exists = 1;
      parent->collection = 1;
      parent->versioned = 1;
      parent->hooks = resource->hooks;
      parent->pool = resource->pool;
      parent->uri = get_parent_path(svn_urlpath__canonicalize(resource->uri,
                                                              resource->pool),
                                    TRUE, resource->pool);
      parent->info = parentinfo;

      parentinfo->uri_path =
        svn_stringbuf_create(
               get_parent_path(
                   svn_urlpath__canonicalize(resource->info->uri_path->data,
                                            resource->pool),
                   TRUE, resource->pool),
               resource->pool);
      parentinfo->repos = resource->info->repos;
      parentinfo->root = resource->info->root;
      parentinfo->r = resource->info->r;
      parentinfo->svn_client_options = resource->info->svn_client_options;
      parentinfo->repos_path = get_parent_path(resource->info->repos_path,
                                               FALSE, resource->pool);

      *parent_resource = parent;
      break;

    case DAV_RESOURCE_TYPE_WORKING:
      /* The "/" occurring within the URL of working resources is part of
         its identifier; it does not establish parent resource relationships.
         All working resources have the same parent, which is:
         http://host.name/path2repos/$svn/wrk/
      */
      *parent_resource =
        create_private_resource(resource, DAV_SVN_RESTYPE_WRK_COLLECTION);
      break;

    case DAV_RESOURCE_TYPE_ACTIVITY:
      *parent_resource =
        create_private_resource(resource, DAV_SVN_RESTYPE_ACT_COLLECTION);
      break;

    case DAV_RESOURCE_TYPE_PRIVATE:
      if ((resource->info->restype == DAV_SVN_RESTYPE_TXN_COLLECTION)
          || (resource->info->restype == DAV_SVN_RESTYPE_REV_COLLECTION))
        *parent_resource =
          create_private_resource(resource, resource->info->restype);
      /* ### FIXME:  Need parents for other private resource types. */
      break;

    default:
      /* ### FIXME:  Need parents for other resource types. */
      break;
    }

  /* If we didn't create parent resource above, complain. */
  if (! *parent_resource)
    return dav_svn__new_error(resource->pool, HTTP_INTERNAL_SERVER_ERROR, 0, 0,
                              apr_psprintf(resource->pool,
                                           "get_parent_resource was called for "
                                           "%s (type %d)",
                                           resource->uri, resource->type));

  return NULL;
}


/* does RES2 live in the same repository as RES1? */
static int
is_our_resource(const dav_resource *res1, const dav_resource *res2)
{
  if (res1->hooks != res2->hooks
      || strcmp(res1->info->repos->fs_path, res2->info->repos->fs_path) != 0)
    {
      /* a different provider, or a different FS repository */
      return 0;
    }

  /* coalesce the repository */
  if (res1->info->repos != res2->info->repos)
    {
      /* ### might be nice to have a pool which we can clear to toss
         ### out the old, redundant repos/fs.  */

      /* have res2 point to res1's filesystem */
      res2->info->repos = res1->info->repos;

      /* res2's fs_root object is now invalid.  regenerate it using
         the now-shared filesystem. */
      if (res2->info->root.txn_name)
        {
          /* reopen the txn by name */
          svn_error_clear(svn_fs_open_txn(&(res2->info->root.txn),
                                          res2->info->repos->fs,
                                          res2->info->root.txn_name,
                                          res2->info->repos->pool));

          /* regenerate the txn "root" object */
          svn_error_clear(svn_fs_txn_root(&(res2->info->root.root),
                                          res2->info->root.txn,
                                          res2->info->repos->pool));
        }
      else if (res2->info->root.rev)
        {
          /* default:  regenerate the revision "root" object */
          svn_error_clear(svn_fs_revision_root(&(res2->info->root.root),
                                               res2->info->repos->fs,
                                               res2->info->root.rev,
                                               res2->info->repos->pool));
        }
    }

  return 1;
}


static int
is_same_resource(const dav_resource *res1, const dav_resource *res2)
{
  if (!is_our_resource(res1, res2))
    return 0;

  /* ### what if the same resource were reached via two URIs? */

  return svn_stringbuf_compare(res1->info->uri_path, res2->info->uri_path);
}


static int
is_parent_resource(const dav_resource *res1, const dav_resource *res2)
{
  apr_size_t len1 = strlen(res1->info->uri_path->data);
  apr_size_t len2;

  if (!is_our_resource(res1, res2))
    return 0;

  /* ### what if a resource were reached via two URIs? we ought to define
     ### parent/child relations for resources independent of URIs.
     ### i.e. define a "canonical" location for each resource, then return
     ### the parent based on that location. */

  /* res2 is one of our resources, we can use its ->info ptr */
  len2 = strlen(res2->info->uri_path->data);

  return (len2 > len1
          && memcmp(res1->info->uri_path->data, res2->info->uri_path->data,
                    len1) == 0
          && res2->info->uri_path->data[len1] == '/');
}


static dav_error *
open_stream(const dav_resource *resource,
            dav_stream_mode mode,
            dav_stream **stream)
{
  svn_node_kind_t kind;
  dav_error *derr;
  svn_error_t *serr;

  if (mode == DAV_MODE_WRITE_TRUNC || mode == DAV_MODE_WRITE_SEEKABLE)
    {
      if (resource->type != DAV_RESOURCE_TYPE_WORKING)
        {
          return dav_svn__new_error(resource->pool, HTTP_METHOD_NOT_ALLOWED,
                                    0, 0,
                                    "Resource body changes may only be made to "
                                    "working resources (at this time).");
        }
      if (!resource->info->root.root)
        {
          return dav_svn__new_error(resource->pool, HTTP_METHOD_NOT_ALLOWED,
                                    0, 0,
                                    "Resource body changes may only be made to "
                                    "checked-out resources (at this time).");
        }
    }

  /* ### TODO:  Can we support range writes someday? */
  if (mode == DAV_MODE_WRITE_SEEKABLE)
    {
      return dav_svn__new_error(resource->pool, HTTP_NOT_IMPLEMENTED, 0, 0,
                                "Resource body writes cannot use ranges "
                                "(at this time).");
    }

  /* start building the stream structure */
  *stream = apr_pcalloc(resource->pool, sizeof(**stream));
  (*stream)->res = resource;

  derr = fs_check_path(&kind, resource->info->root.root,
                       resource->info->repos_path, resource->pool);
  if (derr != NULL)
    return derr;

  if (kind == svn_node_none) /* No existing file. */
    {
      serr = svn_fs_make_file(resource->info->root.root,
                              resource->info->repos_path,
                              resource->pool);

      if (serr != NULL)
        {
          return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                      "Could not create file within the "
                                      "repository.",
                                      resource->pool);
        }
    }

  /* if the working-resource was auto-checked-out (i.e. came into
     existence through the autoversioning feature), then possibly set
     the svn:mime-type property based on whatever value mod_mime has
     chosen.  If the path already has an svn:mime-type property
     set, do nothing. */
  if (resource->info->auto_checked_out
      && resource->info->r->content_type)
    {
      svn_string_t *mime_type;

      serr = svn_fs_node_prop(&mime_type,
                              resource->info->root.root,
                              resource->info->repos_path,
                              SVN_PROP_MIME_TYPE,
                              resource->pool);

      if (serr != NULL)
        {
          return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                      "Error fetching mime-type property.",
                                      resource->pool);
        }

      if (!mime_type)
        {
          serr = svn_fs_change_node_prop(resource->info->root.root,
                                         resource->info->repos_path,
                                         SVN_PROP_MIME_TYPE,
                                         svn_string_create
                                             (resource->info->r->content_type,
                                              resource->pool),
                                         resource->pool);
          if (serr != NULL)
            {
              return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                          "Could not set mime-type property.",
                                          resource->pool);
            }
        }
    }

  serr = svn_fs_apply_textdelta(&(*stream)->delta_handler,
                                &(*stream)->delta_baton,
                                resource->info->root.root,
                                resource->info->repos_path,
                                resource->info->base_checksum,
                                resource->info->result_checksum,
                                resource->pool);

  if (serr != NULL)
    {
      return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                  "Could not prepare to write the file",
                                  resource->pool);
    }

  /* if the incoming data is an SVNDIFF, then create a stream that
     will process the data into windows and invoke the FS window handler
     when a window is ready. */
  /* ### we need a better way to check the content-type! this is bogus
     ### because we're effectively looking at the request_rec. doubly
     ### bogus because this means you cannot open arbitrary streams and
     ### feed them content (the type is always tied to a request_rec).
     ### probably ought to pass the type to open_stream */
  if (resource->info->is_svndiff)
    {
      (*stream)->wstream =
        svn_txdelta_parse_svndiff((*stream)->delta_handler,
                                  (*stream)->delta_baton,
                                  TRUE,
                                  resource->pool);
    }

  return NULL;
}


static dav_error *
close_stream(dav_stream *stream, int commit)
{
  svn_error_t *serr;
  apr_pool_t *pool = stream->res->pool;

  if (stream->rstream != NULL)
    {
      serr = svn_stream_close(stream->rstream);
      if (serr)
        return dav_svn__convert_err
          (serr, HTTP_INTERNAL_SERVER_ERROR,
           "mod_dav_svn close_stream: error closing read stream",
           pool);
    }

  /* if we have a write-stream, then closing it also takes care of the
     handler (so make sure not to send a NULL to it, too) */
  if (stream->wstream != NULL)
    {
      serr = svn_stream_close(stream->wstream);
      if (serr)
        return dav_svn__convert_err
          (serr, HTTP_INTERNAL_SERVER_ERROR,
           "mod_dav_svn close_stream: error closing write stream",
           pool);
    }
  else if (stream->delta_handler != NULL)
    {
      serr = (*stream->delta_handler)(NULL, stream->delta_baton);
      if (serr)
        return dav_svn__convert_err
          (serr, HTTP_INTERNAL_SERVER_ERROR,
           "mod_dav_svn close_stream: error sending final (null) delta window",
           pool);
    }

  if (stream->wstream != NULL || stream->delta_handler != NULL)
    {
      request_rec *r = stream->res->info->r;
      svn_checksum_t *checksum;

      serr = svn_fs_file_checksum(&checksum, svn_checksum_md5,
                                  stream->res->info->root.root,
                                  stream->res->info->repos_path,
                                  FALSE, pool);
      if (serr)
        return dav_svn__convert_err
          (serr, HTTP_INTERNAL_SERVER_ERROR,
            "mod_dav_svn close_stream: error getting file checksum",
            pool);

      if (checksum)
        apr_table_set(r->headers_out, SVN_DAV_RESULT_FULLTEXT_MD5_HEADER,
                      svn_checksum_to_cstring(checksum, pool));
    }

  return NULL;
}


static dav_error *
write_stream(dav_stream *stream, const void *buf, apr_size_t bufsize)
{
  svn_error_t *serr;
  apr_pool_t *pool = stream->res->pool;

  if (stream->wstream != NULL)
    {
      serr = svn_stream_write(stream->wstream, buf, &bufsize);
      /* ### would the returned bufsize ever not match the requested amt? */
    }
  else
    {
      svn_txdelta_window_t window = { 0 };
      svn_txdelta_op_t op;
      svn_string_t data;

      data.data = buf;
      data.len = bufsize;

      op.action_code = svn_txdelta_new;
      op.offset = 0;
      op.length = bufsize;

      window.tview_len = bufsize;   /* result will be this long */
      window.num_ops = 1;
      window.ops = &op;
      window.new_data = &data;

      serr = (*stream->delta_handler)(&window, stream->delta_baton);
    }

  if (serr)
    {
      return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                  "could not write the file contents",
                                  pool);
    }
  return NULL;
}


static dav_error *
seek_stream(dav_stream *stream, apr_off_t abs_position)
{
  /* ### fill this in */

  return dav_svn__new_error(stream->res->pool, HTTP_NOT_IMPLEMENTED, 0, 0,
                            "Resource body read/write cannot use ranges "
                            "(at this time)");
}

/* Returns whether the DAV resource lacks potential for generation of
   an ETag (defined as any of the following):
   - it doesn't exist
   - the resource type isn't REGULAR or VERSION
   - the resource is a Baseline */
#define RESOURCE_LACKS_ETAG_POTENTIAL(resource) \
  (!resource->exists \
   || (resource->type != DAV_RESOURCE_TYPE_REGULAR \
       && resource->type != DAV_RESOURCE_TYPE_VERSION) \
   || (resource->type == DAV_RESOURCE_TYPE_VERSION \
       && resource->baselined))


const char *
dav_svn__getetag(const dav_resource *resource, apr_pool_t *pool)
{
  svn_error_t *serr;
  svn_revnum_t created_rev;

  if (RESOURCE_LACKS_ETAG_POTENTIAL(resource))
    return "";

  /* ### what kind of etag to return for activities, etc.? */

  if ((serr = svn_fs_node_created_rev(&created_rev, resource->info->root.root,
                                      resource->info->repos_path,
                                      pool)))
    {
      /* ### what to do? */
      svn_error_clear(serr);
      return "";
    }

  /* Use the "weak" format of the etag for collections because our GET
     requests on collections include dynamic data (the HEAD revision,
     the build version of Subversion, etc.). */
  return apr_psprintf(pool, "%s\"%ld/%s\"",
                      resource->collection ? "W/" : "",
                      created_rev,
                      apr_xml_quote_string(pool,
                                           resource->info->repos_path, 1));
}


/* Since dav_svn__getetag() takes a pool argument, this wrapper is for
   the mod_dav hooks vtable entry, which does not. */
static const char *
getetag_pathetic(const dav_resource *resource)
{
  return dav_svn__getetag(resource, resource->pool);
}

/* Helper for set_headers(). Returns TRUE if request R to RESOURCE can be
 * cached. Returns FALSe otherwise. */
static svn_boolean_t
is_cacheable(request_rec *r, const dav_resource *resource)
{
  /* Non-idempotent resource cannot be cached because actual
     target could change when youngest revision or transacation
     will change. */
  if (!resource->info->idempotent)
    return FALSE;

  /* Our GET requests on collections include dynamic data (the
     HEAD revision, the build version of Subversion, etc.).
     Directory content is also subject of authz filtering.*/
  if (resource->collection)
    return FALSE;

  if (resource->type == DAV_RESOURCE_TYPE_REGULAR ||
      resource->type == DAV_RESOURCE_TYPE_VERSION)
      return TRUE;
  else
      return FALSE;
}

static dav_error *
set_headers(request_rec *r, const dav_resource *resource)
{
  svn_error_t *serr;
  svn_filesize_t length;
  const char *mimetype = NULL;

  /* As version resources don't change, encourage caching. */
  if (is_cacheable(r, resource))
    /* Cache resource for one week (specified in seconds). */
    apr_table_setn(r->headers_out, "Cache-Control", "max-age=604800");
  else
    apr_table_setn(r->headers_out, "Cache-Control", "max-age=0");

  if (!resource->exists)
    return NULL;

  /* generate our etag and place it into the output */
  apr_table_setn(r->headers_out, "ETag",
                 dav_svn__getetag(resource, resource->pool));

  /* we accept byte-ranges */
  apr_table_setn(r->headers_out, "Accept-Ranges", "bytes");

  /* For a directory, we will send text/html or text/xml. If we have a delta
     base, then we will always be generating an svndiff.  Otherwise,
     we need to fetch the appropriate MIME type from the resource's
     properties (and use text/plain if it isn't there). */
  if (resource->collection)
    {
      if (resource->info->repos->xslt_uri)
        mimetype = "text/xml";
      else
        mimetype = "text/html; charset=UTF-8";
    }
  else if (resource->info->delta_base != NULL)
    {
      dav_svn__uri_info info;

      /* First order of business is to parse it. */
      serr = dav_svn__simple_parse_uri(&info, resource,
                                       resource->info->delta_base,
                                       resource->pool);

      /* If we successfully parse the base URL, then send an svndiff. */
      if ((serr == NULL) && (info.rev != SVN_INVALID_REVNUM))
        {
          mimetype = SVN_SVNDIFF_MIME_TYPE;

          /* Note the base that this svndiff is based on, and tell any
             intermediate caching proxies that this header is
             significant.  */
          apr_table_setn(r->headers_out, "Vary", SVN_DAV_DELTA_BASE_HEADER);
          apr_table_setn(r->headers_out, SVN_DAV_DELTA_BASE_HEADER,
                         resource->info->delta_base);
        }
      svn_error_clear(serr);
    }

  if ((mimetype == NULL)
      && ((resource->type == DAV_RESOURCE_TYPE_VERSION)
          || (resource->type == DAV_RESOURCE_TYPE_REGULAR))
      && (resource->info->repos_path != NULL))
    {
      svn_string_t *value;

      serr = svn_fs_node_prop(&value,
                              resource->info->root.root,
                              resource->info->repos_path,
                              SVN_PROP_MIME_TYPE,
                              resource->pool);
      if (serr != NULL)
        return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                    "could not fetch the resource's MIME type",
                                    resource->pool);

      if (value)
        mimetype = value->data;
      else if ((! resource->info->repos->is_svn_client)
               && r->content_type)
        mimetype = r->content_type;

      /* If we found a MIME type, we'll make sure it's Subversion-friendly. */
      if (mimetype)
        {
          if ((serr = svn_mime_type_validate(mimetype, resource->pool)))
            {
              /* Probably serr->apr == SVN_ERR_BAD_MIME_TYPE, but there's
                 no point even checking.  No matter what the error is, we
                 can't use this MIME type.  */
              svn_error_clear(serr);
              mimetype = NULL;
            }
        }

      /* We've found/calculated/validated no usable MIME type.  We
         could fall back to "application/octet-stream" (aka "bag o'
         bytes"), but many browsers have grown to expect "text/plain"
         to mean "*shrug*", and kick off their own MIME type detection
         routines when they see it.  So we'll use "text/plain".

         ### Why not just avoid sending a Content-type at all?  Is
         ### that just bad form for HTTP?  */
      if (! mimetype)
        mimetype = "text/plain";


      /* if we aren't sending a diff and aren't expanding keywords,
         then we know the exact length of the file, so set up the
         Content-Length header. */
      if (! resource->info->keyword_subst)
        {
          serr = svn_fs_file_length(&length,
                                    resource->info->root.root,
                                    resource->info->repos_path,
                                    resource->pool);
          if (serr != NULL)
            {
              return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                          "could not fetch the resource length",
                                          resource->pool);
            }
          ap_set_content_length(r, (apr_off_t) length);
        }
    }

  /* set the discovered MIME type */
  /* ### it would be best to do this during the findct phase... */
  ap_set_content_type(r, mimetype);

  return NULL;
}


typedef struct diff_ctx_t {
  dav_svn__output *output;
  apr_bucket_brigade *bb;
} diff_ctx_t;


static svn_error_t *  __attribute__((warn_unused_result))
write_to_filter(void *baton, const char *buffer, apr_size_t *len)
{
  diff_ctx_t *dc = baton;

  /* take the current data and shove it into the filter */
  SVN_ERR(dav_svn__brigade_write(dc->bb, dc->output, buffer, *len));

  return SVN_NO_ERROR;
}


static svn_error_t *  __attribute__((warn_unused_result))
close_filter(void *baton)
{
  diff_ctx_t *dc = baton;
  apr_bucket *bkt;

  /* done with the file. write an EOS bucket now. */
  bkt = apr_bucket_eos_create(dav_svn__output_get_bucket_alloc(dc->output));
  APR_BRIGADE_INSERT_TAIL(dc->bb, bkt);
  SVN_ERR(dav_svn__output_pass_brigade(dc->output, dc->bb));

  return SVN_NO_ERROR;
}


static svn_error_t *
emit_collection_head(const dav_resource *resource,
                     apr_bucket_brigade *bb,
                     dav_svn__output *output,
                     svn_boolean_t gen_html,
                     apr_pool_t *pool)
{
  /* XML schema for the directory index if xslt_uri is set:

     <?xml version="1.0"?>
     <?xml-stylesheet type="text/xsl" href="[info->repos->xslt_uri]"?> */
  static const char xml_index_dtd[] =
    "<!DOCTYPE svn [\n"
    "  <!ELEMENT svn   (index)>\n"
    "  <!ATTLIST svn   version CDATA #REQUIRED\n"
    "                  href    CDATA #REQUIRED>\n"
    "  <!ELEMENT index (updir?, (file | dir)*)>\n"
    "  <!ATTLIST index name    CDATA #IMPLIED\n"
    "                  path    CDATA #IMPLIED\n"
    "                  rev     CDATA #IMPLIED\n"
    "                  base    CDATA #IMPLIED>\n"
    "  <!ELEMENT updir EMPTY>\n"
    "  <!ATTLIST updir href    CDATA #REQUIRED>\n"
    "  <!ELEMENT file  EMPTY>\n"
    "  <!ATTLIST file  name    CDATA #REQUIRED\n"
    "                  href    CDATA #REQUIRED>\n"
    "  <!ELEMENT dir   EMPTY>\n"
    "  <!ATTLIST dir   name    CDATA #REQUIRED\n"
    "                  href    CDATA #REQUIRED>\n"
    "]>\n";

  if (gen_html)
    {
      const char *title;
      if (resource->info->repos_path == NULL)
        title = "unknown location";
      else
        title = resource->info->repos_path;

      if (resource->info->restype != DAV_SVN_RESTYPE_PARENTPATH_COLLECTION)
        {
          if (SVN_IS_VALID_REVNUM(resource->info->root.rev))
            title = apr_psprintf(pool,
                                 "Revision %ld: %s",
                                 resource->info->root.rev, title);
          if (resource->info->repos->repo_basename)
            title = apr_psprintf(pool, "%s - %s",
                                 resource->info->repos->repo_basename,
                                 title);
          if (resource->info->repos->repo_name)
            title = apr_psprintf(pool, "%s: %s",
                                 resource->info->repos->repo_name,
                                 title);
        }

      SVN_ERR(dav_svn__brigade_printf(bb, output,
                                      "<html><head><title>%s</title></head>\n"
                                      "<body>\n <h2>%s</h2>\n <ul>\n",
                                      title, title));
    }
  else
    {
      const char *name = resource->info->repos->repo_name;
      const char *href = resource->info->repos_path;
      const char *base = resource->info->repos->repo_basename;

      SVN_ERR(dav_svn__brigade_puts(bb, output, "<?xml version=\"1.0\"?>\n"));
      SVN_ERR(dav_svn__brigade_printf(bb, output,
                                      "<?xml-stylesheet type=\"text/xsl\" "
                                      "href=\"%s\"?>\n",
                                      resource->info->repos->xslt_uri));
      SVN_ERR(dav_svn__brigade_puts(bb, output, xml_index_dtd));
      SVN_ERR(dav_svn__brigade_puts(bb, output,
                         "<svn version=\"" SVN_VERSION "\"\n"
                         "     href=\"http://subversion.apache.org/\">\n"));
      SVN_ERR(dav_svn__brigade_puts(bb, output, "  <index"));

      if (name)
        SVN_ERR(dav_svn__brigade_printf(bb, output,
                                        " name=\"%s\"",
                                        apr_xml_quote_string(resource->pool,
                                                             name, 1)));
      if (SVN_IS_VALID_REVNUM(resource->info->root.rev))
        SVN_ERR(dav_svn__brigade_printf(bb, output, " rev=\"%ld\"",
                                        resource->info->root.rev));
      if (href)
        SVN_ERR(dav_svn__brigade_printf(bb, output, " path=\"%s\"",
                                        apr_xml_quote_string(resource->pool,
                                                             href, 1)));
      if (base)
        SVN_ERR(dav_svn__brigade_printf(bb, output, " base=\"%s\"", base));

      SVN_ERR(dav_svn__brigade_puts(bb, output, ">\n"));
    }

  if ((resource->info->restype != DAV_SVN_RESTYPE_PARENTPATH_COLLECTION)
      && resource->info->repos_path
      && ((resource->info->repos_path[1] != '\0')
          || dav_svn__get_list_parentpath_flag(resource->info->r)))
    {
      const char *href;
      if (resource->info->pegged)
        {
          href = apr_psprintf(pool, "../?p=%ld", resource->info->root.rev);
        }
      else
        {
          href = "../";
        }

      if (gen_html)
        {
          SVN_ERR(dav_svn__brigade_printf(bb, output,
                                          "  <li><a href=\"%s\">..</a></li>\n",
                                          href));
        }
      else
        {
          SVN_ERR(dav_svn__brigade_printf(bb, output,
                                          "    <updir href=\"%s\"/>\n",
                                          href));
        }
    }

  return SVN_NO_ERROR;
}


static svn_error_t *
emit_collection_entry(const dav_resource *resource,
                      apr_bucket_brigade *bb,
                      dav_svn__output *output,
                      const svn_fs_dirent_t *entry,
                      svn_boolean_t gen_html,
                      apr_pool_t *pool)
{
  const char *name = entry->name;
  const char *href = name;
  svn_boolean_t is_dir = (entry->kind == svn_node_dir);

  /* append a trailing slash onto the name for directories. we NEED
     this for the href portion so that the relative reference will
     descend properly. for the visible portion, it is just nice. */
  /* ### The xml output doesn't like to see a trailing slash on
     ### the visible portion, so avoid that. */
  if (is_dir)
    href = apr_pstrcat(pool, href, "/", SVN_VA_NULL);

  if (gen_html)
    name = href;

  /* We quote special characters in both XML and HTML. */
  name = apr_xml_quote_string(pool, name, !gen_html);

  /* According to httpd-2.0.54/include/httpd.h, ap_os_escape_path()
     behaves differently on different platforms.  It claims to
     "convert an OS path to a URL in an OS dependant way".
     Nevertheless, there appears to be only one implementation
     of the function in httpd, and the code seems completely
     platform independent, so we'll assume it's appropriate for
     mod_dav_svn to use it to quote outbound paths. */
  href = ap_os_escape_path(pool, href, 0);
  href = apr_xml_quote_string(pool, href, 1);

  if (gen_html)
    {
      /* If our directory was access using the public peg-rev
         CGI query interface, we'll let its dirents carry that
         peg-rev, too. */
      if (resource->info->pegged)
        {
          SVN_ERR(dav_svn__brigade_printf(bb, output,
                     "  <li><a href=\"%s?p=%ld\">%s</a></li>\n",
                     href, resource->info->root.rev, name));
        }
      else
        {
          SVN_ERR(dav_svn__brigade_printf(bb, output,
                     "  <li><a href=\"%s\">%s</a></li>\n",
                     href, name));
        }
    }
  else
    {
      const char *const tag = (is_dir ? "dir" : "file");

      /* This is where we could search for props */

      /* If our directory was access using the public peg-rev
         CGI query interface, we'll let its dirents carry that
         peg-rev, too. */
      if (resource->info->pegged)
        {
          SVN_ERR(dav_svn__brigade_printf(bb, output,
                     "    <%s name=\"%s\" href=\"%s?p=%ld\" />\n",
                     tag, name, href, resource->info->root.rev));
        }
      else
        {
          SVN_ERR(dav_svn__brigade_printf(bb, output,
                     "    <%s name=\"%s\" href=\"%s\" />\n",
                     tag, name, href));
        }
    }

  return SVN_NO_ERROR;
}


static svn_error_t *
emit_collection_tail(const dav_resource *resource,
                     apr_bucket_brigade *bb,
                     dav_svn__output *output,
                     svn_boolean_t gen_html,
                     apr_pool_t *pool)
{
  if (gen_html)
    {
      if (strcmp(ap_psignature("FOO", resource->info->r), "") != 0)
        {
          /* Apache's signature generation code didn't eat our prefix.
             ServerSignature must be enabled.  Print our version info.

             WARNING: This is a kludge!! ap_psignature() doesn't promise
             to return the empty string when ServerSignature is off.  We
             know it does by code inspection, but this behavior is subject
             to change. (Perhaps we should try to get the Apache folks to
             make this promise, though.  Seems harmless/useful enough...)
          */
          SVN_ERR(dav_svn__brigade_puts(bb, output,
                   " </ul>\n <hr noshade><em>Powered by "
                   "<a href=\"http://subversion.apache.org/\">"
                   "Apache Subversion"
                   "</a> version " SVN_VERSION "."
                   "</em>\n</body></html>"));
        }
      else
        SVN_ERR(dav_svn__brigade_puts(bb, output, " </ul>\n</body></html>"));
    }
  else
    SVN_ERR(dav_svn__brigade_puts(bb, output, "  </index>\n</svn>\n"));

  return SVN_NO_ERROR;
}


static dav_error *
deliver(const dav_resource *resource, ap_filter_t *unused)
{
  svn_error_t *serr;
  apr_bucket_brigade *bb;
  apr_bucket *bkt;
  dav_svn__output *output;

  /* Check resource type */
  if (resource->baselined
      || (resource->type != DAV_RESOURCE_TYPE_REGULAR
          && resource->type != DAV_RESOURCE_TYPE_VERSION
          && resource->type != DAV_RESOURCE_TYPE_WORKING
          && resource->info->restype != DAV_SVN_RESTYPE_PARENTPATH_COLLECTION))
    {
      return dav_svn__new_error(resource->pool, HTTP_CONFLICT, 0, 0,
                                "Cannot GET this type of resource.");
    }

  output = dav_svn__output_create(resource->info->r, resource->pool);

  if (resource->collection)
    {
      const int gen_html = !resource->info->repos->xslt_uri;
      apr_hash_t *entries;
      apr_pool_t *iterpool;
      apr_array_header_t *sorted;
      svn_revnum_t dir_rev = SVN_INVALID_REVNUM;
      int i;

      /* <svn version="1.3.0 (dev-build)"
              href="http://subversion.apache.org">
           <index name="[info->repos->repo_name]"
                  path="[info->repos_path]"
                  rev="[info->root.rev]">
             <file name="foo" href="foo" />
             <dir name="bar" href="bar/" />
           </index>
         </svn> */


      /* ### TO-DO:  check for a new mod_dav_svn directive here also. */
      if (resource->info->restype == DAV_SVN_RESTYPE_PARENTPATH_COLLECTION)
        {
          apr_hash_index_t *hi;
          apr_hash_t *dirents;
          const char *fs_parent_path =
            dav_svn__get_fs_parent_path(resource->info->r);

          serr = svn_io_get_dirents3(&dirents, fs_parent_path, TRUE,
                                     resource->pool, resource->pool);
          if (serr != NULL)
            return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                        "could not fetch dirents of "
                                        "SVNParentPath", resource->pool);

          /* convert an io dirent hash to an fs dirent hash. */
          entries = apr_hash_make(resource->pool);
          for (hi = apr_hash_first(resource->pool, dirents);
               hi; hi = apr_hash_next(hi))
            {
              const void *key;
              void *val;
              svn_io_dirent_t *dirent;
              svn_fs_dirent_t *ent = apr_pcalloc(resource->pool, sizeof(*ent));

              apr_hash_this(hi, &key, NULL, &val);
              dirent = val;

              if (dirent->kind == svn_node_file && dirent->special)
                {
                  svn_node_kind_t resolved_kind;
                  const char *link_path =
                    svn_dirent_join(fs_parent_path, key, resource->pool);

                  serr = svn_io_check_resolved_path(link_path, &resolved_kind,
                                                    resource->pool);
                  if (serr)
                    return dav_svn__convert_err(serr,
                                                HTTP_INTERNAL_SERVER_ERROR,
                                                "could not resolve symlink "
                                                "dirent of SVNParentPath",
                                                resource->pool);
                  if (resolved_kind != svn_node_dir)
                    continue;

                  dirent->kind = svn_node_dir;
                }
              else if (dirent->kind != svn_node_dir)
                continue;

              ent->name = key;
              ent->id = NULL;     /* ### does it matter? */
              ent->kind = dirent->kind;

              svn_hash_sets(entries, key, ent);
            }

        }
      else
        {
          dir_rev = svn_fs_revision_root_revision(resource->info->root.root);
          serr = svn_fs_dir_entries(&entries, resource->info->root.root,
                                    resource->info->repos_path, resource->pool);
          if (serr != NULL)
            return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                        "could not fetch directory entries",
                                        resource->pool);
        }

      bb = apr_brigade_create(resource->pool,
                              dav_svn__output_get_bucket_alloc(output));

      serr = emit_collection_head(resource, bb, output, gen_html,
                                  resource->pool);
      if (serr != NULL)
        return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                    "could not output collection",
                                    resource->pool);

      /* get a sorted list of the entries */
      sorted = svn_sort__hash(entries, svn_sort_compare_items_as_paths,
                              resource->pool);

      iterpool = svn_pool_create(resource->pool);

      for (i = 0; i < sorted->nelts; ++i)
        {
          const svn_sort__item_t *item = &APR_ARRAY_IDX(sorted, i,
                                                        const svn_sort__item_t);
          const svn_fs_dirent_t *entry = item->value;
          const char *name = item->key;
          const char *repos_relpath = NULL;

          svn_pool_clear(iterpool);

          /* DIR_REV is set to a valid revision if we're looking at
             the entries of a versioned directory.  Otherwise, we're
             looking at a parent-path listing. */
          if (SVN_IS_VALID_REVNUM(dir_rev))
            {
              repos_relpath = svn_fspath__join(resource->info->repos_path,
                                               name, iterpool);
              if (! dav_svn__allow_read(resource->info->r,
                                        resource->info->repos,
                                        repos_relpath,
                                        dir_rev,
                                        iterpool))
                continue;
            }
          else
            {
                if (! dav_svn__allow_list_repos(resource->info->r,
                                                entry->name, iterpool))
                  continue;
            }

          serr = emit_collection_entry(resource, bb, output, entry, gen_html,
                                       iterpool);
          if (serr != NULL)
            return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                        "could not output collection entry",
                                        resource->pool);
        }

      svn_pool_destroy(iterpool);

      serr = emit_collection_tail(resource, bb, output, gen_html,
                                  resource->pool);
      if (serr != NULL)
        return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                    "could not output collection",
                                    resource->pool);

      bkt = apr_bucket_eos_create(dav_svn__output_get_bucket_alloc(output));
      APR_BRIGADE_INSERT_TAIL(bb, bkt);
      serr = dav_svn__output_pass_brigade(output, bb);
      if (serr != NULL)
        return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                    "Could not write EOS to filter.",
                                    resource->pool);

      return NULL;
    }


  /* If we have a base for a delta, then we want to compute an svndiff
     between the provided base and the requested resource. For a simple
     request, then we just grab the file contents. */
  if (resource->info->delta_base != NULL)
    {
      dav_svn__uri_info info;
      svn_fs_root_t *root;
      svn_boolean_t is_file;
      svn_txdelta_stream_t *txd_stream;
      svn_stream_t *o_stream;
      svn_txdelta_window_handler_t handler;
      void * h_baton;
      diff_ctx_t dc = { 0 };

      /* First order of business is to parse it. */
      serr = dav_svn__simple_parse_uri(&info, resource,
                                       resource->info->delta_base,
                                       resource->pool);

      /* If we successfully parse the base URL, then send an svndiff. */
      if ((serr == NULL) && (info.rev != SVN_INVALID_REVNUM))
        {
          /* We are always accessing the base resource by ID, so open
             an ID root. */
          serr = svn_fs_revision_root(&root, resource->info->repos->fs,
                                      info.rev, resource->pool);
          if (serr != NULL)
            return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                        "could not open a root for the base",
                                        resource->pool);

          /* verify that it is a file */
          serr = svn_fs_is_file(&is_file, root, info.repos_path,
                                resource->pool);
          if (serr != NULL)
            return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                        "could not determine if the base "
                                        "is really a file",
                                        resource->pool);
          if (!is_file)
            return dav_svn__new_error(resource->pool, HTTP_BAD_REQUEST, 0, 0,
                                      apr_psprintf(resource->pool,
                                      "the delta base of '%s' does not refer "
                                      "to a file in revision %ld",
                                      info.repos_path, info.rev));

          /* Okay. Let's open up a delta stream for the client to read. */
          serr = svn_fs_get_file_delta_stream(&txd_stream,
                                              root, info.repos_path,
                                              resource->info->root.root,
                                              resource->info->repos_path,
                                              resource->pool);
          if (serr != NULL)
            return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                        "could not prepare to read a delta",
                                        resource->pool);

          bb = apr_brigade_create(resource->pool,
                                  dav_svn__output_get_bucket_alloc(output));

          /* create a stream that svndiff data will be written to,
             which will copy it to the network */
          dc.output = output;
          dc.bb = bb;
          o_stream = svn_stream_create(&dc, resource->pool);
          svn_stream_set_write(o_stream, write_to_filter);
          svn_stream_set_close(o_stream, close_filter);

          /* get a handler/baton for writing into the output stream */
          svn_txdelta_to_svndiff3(&handler, &h_baton,
                                  o_stream, resource->info->svndiff_version,
                                  dav_svn__get_compression_level(resource->info->r),
                                  resource->pool);

          /* got everything set up. read in delta windows and shove them into
             the handler, which pushes data into the output stream, which goes
             to the network. */
          serr = svn_txdelta_send_txstream(txd_stream, handler, h_baton,
                                           resource->pool);
          apr_brigade_destroy(bb);

          if (serr != NULL)
            return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                        "could not deliver the txdelta stream",
                                        resource->pool);


          return NULL;
        }
      else
        {
          svn_error_clear(serr);
        }
    }

  /* resource->info->delta_base is NULL, or we had an invalid base URL */
    {
      svn_stream_t *stream;
      char *block;

      serr = svn_fs_file_contents(&stream,
                                  resource->info->root.root,
                                  resource->info->repos_path,
                                  resource->pool);
      if (serr != NULL)
        {
          return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                      "could not prepare to read the file",
                                      resource->pool);
        }

      /* Perform keywords substitution if requested by client */
      if (resource->info->keyword_subst)
        {
          svn_string_t *keywords;

          serr = svn_fs_node_prop(&keywords,
                                  resource->info->root.root,
                                  resource->info->repos_path,
                                  SVN_PROP_KEYWORDS,
                                  resource->pool);
          if (serr != NULL)
            return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                        "could not get fetch '"
                                        SVN_PROP_KEYWORDS "' property for "
                                        "for keywords substitution",
                                        resource->pool);

          if (keywords)
            {
              apr_hash_t *kw;
              svn_revnum_t cmt_rev;
              const char *str_cmt_rev, *str_uri, *str_root;
              const char *cmt_date, *cmt_author;
              apr_time_t when = 0;

              serr = svn_repos_get_committed_info(&cmt_rev,
                                                  &cmt_date,
                                                  &cmt_author,
                                                  resource->info->root.root,
                                                  resource->info->repos_path,
                                                  resource->pool);
              if (serr != NULL)
                return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                            "could not fetch committed info "
                                            "for keywords substitution",
                                            resource->pool);

              serr = svn_time_from_cstring(&when, cmt_date, resource->pool);
              if (serr != NULL)
                return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                            "could not parse committed date "
                                            "for keywords substitution",
                                            resource->pool);
              str_cmt_rev = apr_psprintf(resource->pool, "%ld", cmt_rev);
              str_uri = apr_pstrcat(resource->pool,
                                    resource->info->repos->base_url,
                                    ap_escape_uri(resource->pool,
                                                  resource->info->r->uri),
                                    SVN_VA_NULL);
              str_root = apr_pstrcat(resource->pool,
                                     resource->info->repos->base_url,
                                     resource->info->repos->root_path,
                                     SVN_VA_NULL);

              serr = svn_subst_build_keywords3(&kw, keywords->data,
                                               str_cmt_rev, str_uri, str_root,
                                               when, cmt_author,
                                               resource->pool);
              if (serr != NULL)
                return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                            "could not perform keywords "
                                            "substitution", resource->pool);

              /* Replace the raw file STREAM with a wrapper that
                 handles keyword translation. */
              stream = svn_subst_stream_translated(
                           svn_stream_disown(stream, resource->pool),
                           NULL, FALSE, kw, TRUE, resource->pool);
            }
        }

      /* ### one day in the future, we can create a custom bucket type
         ### which will read from the FS stream on demand */

      block = apr_palloc(resource->pool, SVN__STREAM_CHUNK_SIZE);
      bb = apr_brigade_create(resource->pool,
                              dav_svn__output_get_bucket_alloc(output));

      while (1) {
        apr_size_t bufsize = SVN__STREAM_CHUNK_SIZE;

        /* read from the FS ... */
        serr = svn_stream_read_full(stream, block, &bufsize);
        if (serr != NULL)
          {
            apr_brigade_destroy(bb);
            return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                        "could not read the file contents",
                                        resource->pool);
          }
        if (bufsize == 0)
          break;

        /* write to the filter ... */
        bkt = apr_bucket_transient_create(
          block, bufsize, dav_svn__output_get_bucket_alloc(output));
        APR_BRIGADE_INSERT_TAIL(bb, bkt);
        serr = dav_svn__output_pass_brigade(output, bb);
        if (serr != NULL)
          {
            apr_brigade_destroy(bb);
            /* ### that HTTP code... */
            return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                        "Could not write data to filter.",
                                        resource->pool);
          }
      }

      /* done with the file. write an EOS bucket now. */
      bkt = apr_bucket_eos_create(dav_svn__output_get_bucket_alloc(output));
      APR_BRIGADE_INSERT_TAIL(bb, bkt);
      serr = dav_svn__output_pass_brigade(output, bb);
      if (serr != NULL)
        {
          apr_brigade_destroy(bb);
          /* ### that HTTP code... */
          return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                      "Could not write EOS to filter.",
                                      resource->pool);
        }

      apr_brigade_destroy(bb);
      return NULL;
    }
}


static dav_error *
create_collection(dav_resource *resource)
{
  svn_error_t *serr;
  dav_error *err;

  if (resource->type != DAV_RESOURCE_TYPE_WORKING
      && resource->type != DAV_RESOURCE_TYPE_REGULAR)
    {
      return dav_svn__new_error(resource->pool, HTTP_METHOD_NOT_ALLOWED, 0, 0,
                                "Collections can only be created within a "
                                "working or regular collection (at this "
                                "time).");
    }

  /* ...regular resources allowed only if autoversioning is turned on. */
  if (resource->type == DAV_RESOURCE_TYPE_REGULAR
      && ! (resource->info->repos->autoversioning))
    return dav_svn__new_error(resource->pool, HTTP_METHOD_NOT_ALLOWED, 0, 0,
                              "MKCOL called on regular resource, but "
                              "autoversioning is not active.");

  /* ### note that the parent was checked out at some point, and this
     ### is being preformed relative to the working rsrc for that parent */

  /* Auto-versioning mkcol of regular resource: */
  if (resource->type == DAV_RESOURCE_TYPE_REGULAR)
    {
      /* Change the VCR into a WR, in place.  This creates a txn and
         changes resource->info->root from a rev-root into a txn-root. */
      err = dav_svn__checkout(resource,
                              1 /* auto-checkout */,
                              0, 0, 0, NULL, NULL);
      if (err)
        return err;
    }

  if ((serr = svn_fs_make_dir(resource->info->root.root,
                              resource->info->repos_path,
                              resource->pool)) != NULL)
    {
      /* ### need a better error */
      return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                  "Could not create the collection.",
                                  resource->pool);
    }

  /* Auto-versioning commit of the txn. */
  if (resource->info->auto_checked_out)
    {
      /* This also changes the WR back into a VCR, in place. */
      err = dav_svn__checkin(resource, 0, NULL);
      if (err)
        return err;
    }

  return NULL;
}


static dav_error *
copy_resource(const dav_resource *src,
              dav_resource *dst,
              int depth,
              dav_response **response)
{
  svn_error_t *serr;
  dav_error *err;
  const char *src_repos_path, *dst_repos_path;

  /* ### source must be from a collection under baseline control. the
     ### baseline will (implicitly) indicate the source revision, and the
     ### path will be derived simply from the URL path */

  /* ### the destination's parent must be a working collection */

  /* ### ben goofing around: */
  /*  char *msg;
      apr_psprintf
      (src->pool, "Got a COPY request with src arg '%s' and dst arg '%s'",
      src->uri, dst->uri);

      return dav_svn__new_error(src->pool, HTTP_NOT_IMPLEMENTED, 0, msg);
  */

  /* ### Safeguard: see issue #916, whereby we're allowing an
     auto-checkout of a baseline for PROPPATCHing, *without* creating
     a new baseline afterwards.  We need to safeguard here that nobody
     is calling COPY with the baseline as a Destination! */
  if (dst->baselined && dst->type == DAV_RESOURCE_TYPE_VERSION)
    return dav_svn__new_error(src->pool, HTTP_PRECONDITION_FAILED, 0, 0,
                              "Illegal: COPY Destination is a baseline.");

  if (dst->type == DAV_RESOURCE_TYPE_REGULAR
      && !(dst->info->repos->autoversioning))
    return dav_svn__new_error(dst->pool, HTTP_METHOD_NOT_ALLOWED, 0, 0,
                              "COPY called on regular resource, but "
                              "autoversioning is not active.");

  /* Auto-versioning copy of regular resource: */
  if (dst->type == DAV_RESOURCE_TYPE_REGULAR)
    {
      /* Change the VCR into a WR, in place.  This creates a txn and
         changes dst->info->root from a rev-root into a txn-root. */
      err = dav_svn__checkout(dst,
                              1 /* auto-checkout */,
                              0, 0, 0, NULL, NULL);
      if (err)
        return err;
    }

  src_repos_path = svn_repos_path(src->info->repos->repos, src->pool);
  dst_repos_path = svn_repos_path(dst->info->repos->repos, dst->pool);

  if (strcmp(src_repos_path, dst_repos_path) != 0)
    {
      /* Perhaps the source and dst repos use different path formats? */
      serr = svn_error_compose_create(
                svn_dirent_get_absolute(&src_repos_path, src_repos_path,
                                        src->pool),
                svn_dirent_get_absolute(&dst_repos_path, dst_repos_path,
                                        dst->pool));

      if (!serr && (strcmp(src_repos_path, dst_repos_path) != 0))
          return dav_svn__new_error_svn(
                dst->pool, HTTP_INTERNAL_SERVER_ERROR, 0, 0,
                "Copy source and destination are in different repositories");
    }
  else
      serr = SVN_NO_ERROR;

  if (!serr)
    {
      serr = svn_fs_copy(src->info->root.root,  /* root object of src rev*/
                         src->info->repos_path, /* relative path of src */
                         dst->info->root.root,  /* root object of dst txn*/
                         dst->info->repos_path, /* relative path of dst */
                         src->pool);
    }
  if (serr)
    return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                "Unable to make a filesystem copy.",
                                dst->pool);

  /* Auto-versioning commit of the txn. */
  if (dst->info->auto_checked_out)
    {
      /* This also changes the WR back into a VCR, in place. */
      err = dav_svn__checkin(dst, 0, NULL);
      if (err)
        return err;
    }

  return NULL;
}


static dav_error *
remove_resource(dav_resource *resource, dav_response **response)
{
  svn_error_t *serr;
  dav_error *err;
  apr_hash_t *locks;

  /* Only activities, working resources, regular resources, and
     certain private resources can be deleted... */
  if (! (resource->type == DAV_RESOURCE_TYPE_WORKING
         || resource->type == DAV_RESOURCE_TYPE_REGULAR
         || resource->type == DAV_RESOURCE_TYPE_ACTIVITY
         || (resource->type == DAV_RESOURCE_TYPE_PRIVATE
             && resource->info->restype == DAV_SVN_RESTYPE_TXN_COLLECTION)))
    return dav_svn__new_error(resource->pool, HTTP_METHOD_NOT_ALLOWED, 0, 0,
                              "DELETE called on invalid resource type.");

  /* ...and regular resources only if autoversioning is turned on. */
  if (resource->type == DAV_RESOURCE_TYPE_REGULAR
      && ! (resource->info->repos->autoversioning))
    return dav_svn__new_error(resource->pool, HTTP_METHOD_NOT_ALLOWED, 0, 0,
                              "DELETE called on regular resource, but "
                              "autoversioning is not active.");

  /* Handle activity deletions (early exit). */
  if (resource->type == DAV_RESOURCE_TYPE_ACTIVITY)
    {
      return dav_svn__delete_activity(resource->info->repos,
                                      resource->info->root.activity_id);
    }

  /* Handle deletions of transaction collections (early exit) */
  if (resource->type == DAV_RESOURCE_TYPE_PRIVATE
      && resource->info->restype == DAV_SVN_RESTYPE_TXN_COLLECTION)
    {
      if (resource->info->root.vtxn_name)
        return dav_svn__delete_activity(resource->info->repos,
                                        resource->info->root.vtxn_name);
      else
        return dav_svn__abort_txn(resource->info->repos,
                                  resource->info->root.txn_name,
                                  resource->pool);
    }

  /* ### note that the parent was checked out at some point, and this
     ### is being preformed relative to the working rsrc for that parent */

  /* NOTE: strictly speaking, we cannot determine whether the parent was
     ever checked out, and that this working resource is relative to that
     checked out parent. It is entirely possible the client checked out
     the target resource and just deleted it. Subversion doesn't mind, but
     this does imply we are not enforcing the "checkout the parent, then
     delete from within" semantic. */

  /* Auto-versioning delete of regular resource: */
  if (resource->type == DAV_RESOURCE_TYPE_REGULAR)
    {
      /* Change the VCR into a WR, in place.  This creates a txn and
         changes resource->info->root from a rev-root into a txn-root. */
      err = dav_svn__checkout(resource,
                              1 /* auto-checkout */,
                              0, 0, 0, NULL, NULL);
      if (err)
        return err;
    }

  /* Sanity check: an svn client may have sent a custom request header
     containing the revision of the item it thinks it's deleting.  In
     this case, we enforce the svn-specific semantic that the item
     must be up-to-date. */
  if (SVN_IS_VALID_REVNUM(resource->info->version_name))
    {
      svn_revnum_t created_rev;
      serr = svn_fs_node_created_rev(&created_rev,
                                     resource->info->root.root,
                                     resource->info->repos_path,
                                     resource->pool);
      if (serr)
        return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                    "Could not get created rev of resource",
                                    resource->pool);

      if (resource->info->version_name < created_rev)
        {
          serr = svn_error_createf(SVN_ERR_RA_OUT_OF_DATE, NULL,
                                   resource->collection
                                    ? "Directory '%s' is out of date"
                                    : (resource->exists
                                        ? "File '%s' is out of date"
                                        : "'%s' is out of date"),
                                   resource->info->repos_path);
          return dav_svn__convert_err(serr, HTTP_CONFLICT,
                                      "Can't DELETE out-of-date resource",
                                      resource->pool);
        }
      else if (resource->info->version_name > created_rev)
        {
          svn_revnum_t txn_base_rev;

          txn_base_rev = svn_fs_txn_base_revision(resource->info->root.txn);
          if (resource->info->version_name > txn_base_rev)
            {
              serr = svn_error_createf(SVN_ERR_FS_NO_SUCH_REVISION, NULL,
                                       "No such revision %ld",
                                       resource->info->version_name);

              return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                          "Unknown base revision",
                                          resource->pool);
            }
        }
    }

  /* Before attempting the filesystem delete, we need to push any
     incoming lock-tokens into the filesystem's access_t.  Normally
     they come in via 'If:' header, and get_resource()
     automatically notices them and does this work for us.  In the
     case of a directory deletion, however, older subversion clients
     are sending 'child' lock-tokens in the non-standard DELETE
     request body. */

  err = dav_svn__build_lock_hash(&locks, resource->info->r,
                                 resource->info->repos_path, resource->pool);
  if (err != NULL)
    return err;

  if (apr_hash_count(locks))
    {
      err = dav_svn__push_locks(resource, locks, resource->pool);
      if (err != NULL)
        return err;
    }

  if ((serr = svn_fs_delete(resource->info->root.root,
                            resource->info->repos_path,
                            resource->pool)) != NULL)
    {
      /* ### need a better error */
      return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                  "Could not delete the resource",
                                  resource->pool);
    }

  /* Auto-versioning commit of the txn. */
  if (resource->info->auto_checked_out)
    {
      /* This also changes the WR back into a VCR, in place. */
      err = dav_svn__checkin(resource, 0, NULL);
      if (err)
        return err;
    }

  return NULL;
}


static dav_error *
move_resource(dav_resource *src,
              dav_resource *dst,
              dav_response **response)
{
  svn_error_t *serr;
  dav_error *err;

  /* NOTE: The svn client does not call the MOVE method yet. Strictly
     speaking, we do not need to implement this repository function.
     But we do so anyway, so non-deltaV clients can work against the
     repository when autoversioning is turned on.  Like the svn client,
     itself, we define a move to be a copy + delete within a single txn. */

  /* Because we have no 'atomic' move, we only allow this method on
     two regular resources with autoversioning active.  That way we
     can auto-checkout a single resource and do the copy + delete
     within a single txn.  (If we had two working resources, which txn
     would we use?) */
  if (src->type != DAV_RESOURCE_TYPE_REGULAR
      || dst->type != DAV_RESOURCE_TYPE_REGULAR
      || !(src->info->repos->autoversioning))
    return dav_svn__new_error(dst->pool, HTTP_METHOD_NOT_ALLOWED, 0, 0,
                              "MOVE only allowed on two public URIs, and "
                              "autoversioning must be active.");

  /* Change the dst VCR into a WR, in place.  This creates a txn and
     changes dst->info->root from a rev-root into a txn-root. */
  err = dav_svn__checkout(dst,
                          1 /* auto-checkout */,
                          0, 0, 0, NULL, NULL);
  if (err)
    return err;

  /* Copy the src to the dst. */
  serr = svn_fs_copy(src->info->root.root,  /* the root object of src rev*/
                     src->info->repos_path, /* the relative path of src */
                     dst->info->root.root,  /* the root object of dst txn*/
                     dst->info->repos_path, /* the relative path of dst */
                     src->pool);
  if (serr)
    return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                "Unable to make a filesystem copy.",
                                dst->pool);

  /* Notice: we're deleting the src repos path from the dst's txn_root. */
  if ((serr = svn_fs_delete(dst->info->root.root,
                            src->info->repos_path,
                            dst->pool)) != NULL)
    return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                "Could not delete the src resource.",
                                dst->pool);

  /* Commit:  this also changes the WR back into a VCR, in place. */
  err = dav_svn__checkin(dst, 0, NULL);
  if (err)
    return err;

  return NULL;
}


typedef struct walker_ctx_t {
  /* the input walk parameters */
  const dav_walk_params *params;

  /* reused as we walk */
  dav_walk_resource wres;

  /* the current resource */
  dav_resource res;             /* wres.resource refers here */
  dav_resource_private info;    /* the info in res */
  svn_stringbuf_t *uri;            /* the uri within res */
  svn_stringbuf_t *repos_path;     /* the repos_path within res */

} walker_ctx_t;

/* Recursively walk a resource for walk().  When DEPTH != 0, recurse with
   DEPTH-1 on child nodes. WALK_ROOT should be TRUE for the root and will be
   FALSE for any descendants, to avoid unneeded work for every descendant
   node.
   */
static dav_error *
do_walk(walker_ctx_t *ctx,
        int depth,
        svn_boolean_t walk_root,
        apr_pool_t *scratch_pool)
{
  const dav_walk_params *params = ctx->params;
  int isdir = ctx->res.collection;
  dav_error *err;
  svn_error_t *serr;
  apr_hash_index_t *hi;
  apr_size_t path_len;
  apr_size_t uri_len;
  apr_size_t repos_len;
  apr_hash_t *children;
  apr_pool_t *iterpool;

  /* The current resource is a collection (possibly here thru recursion)
     and this is the invocation for the collection. Alternatively, this is
     the first [and only] entry to do_walk() for a member resource, so
     this will be the invocation for the member. */
  err = (*params->func)(&ctx->wres,
                        isdir ? DAV_CALLTYPE_COLLECTION : DAV_CALLTYPE_MEMBER);
  if (err != NULL)
    return err;

  /* if we are not to recurse, or this is a member, then we're done */
  if (depth == 0 || !isdir)
    return NULL;

  /* ### for now, let's say that working resources have no children. of
     ### course, this isn't true (or "right") for working collections, but
     ### we don't actually need to do a walk right now. */
  if (params->root->type == DAV_RESOURCE_TYPE_WORKING)
    return NULL;

  /* ### need to allow more walking in the future */
  if (params->root->type != DAV_RESOURCE_TYPE_REGULAR)
    {
      return dav_svn__new_error(params->pool, HTTP_METHOD_NOT_ALLOWED, 0, 0,
                                "Walking the resource hierarchy can only be "
                                "done on 'regular' resources [at this time].");
    }

  /* assert: collection resource. isdir == TRUE. repos_path != NULL. */

  /* append "/" to the paths, in preparation for appending child names.
     don't add "/" if the paths are simply "/" */
  if (ctx->info.uri_path->data[ctx->info.uri_path->len - 1] != '/')
    svn_stringbuf_appendcstr(ctx->info.uri_path, "/");
  if (ctx->repos_path->data[ctx->repos_path->len - 1] != '/')
    svn_stringbuf_appendcstr(ctx->repos_path, "/");

  /* NOTE: the URI should already have a trailing "/" */

  /* fix up the dependent pointers */
  ctx->info.repos_path = ctx->repos_path->data;

  /* all of the children exist. also initialize the collection flag. */
  ctx->res.exists = TRUE;
  ctx->res.collection = FALSE;

  /* remember these values so we can chop back to them after each time
     we append a child name to the path/uri/repos */
  path_len = ctx->info.uri_path->len;
  uri_len = ctx->uri->len;
  repos_len = ctx->repos_path->len;

  if (walk_root)
    {
      /* Tell our logging subsystem that we're listing a directory.

      Note: if we cared, we could look at the 'User-Agent:' request
         header and distinguish an svn client ('svn ls') from a generic
         DAV client.  */
      dav_svn__operational_log(&ctx->info,
                               svn_log__get_dir(ctx->info.repos_path,
                                                ctx->info.root.rev,
                                                TRUE, FALSE, SVN_DIRENT_ALL,
                                                scratch_pool));
    }

  /* fetch this collection's children */
  serr = svn_fs_dir_entries(&children, ctx->info.root.root,
                            ctx->info.repos_path, scratch_pool);
  if (serr != NULL)
    return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                "could not fetch collection members",
                                params->pool);

  /* iterate over the children in this collection */
  iterpool = svn_pool_create(scratch_pool);
  for (hi = apr_hash_first(scratch_pool, children); hi; hi = apr_hash_next(hi))
    {
      const void *key;
      apr_ssize_t klen;
      void *val;
      svn_fs_dirent_t *dirent;

      svn_pool_clear(iterpool);

      /* fetch one of the children */
      apr_hash_this(hi, &key, &klen, &val);
      dirent = val;

      /* authorize access to this resource, if applicable */
      if (params->walk_type & DAV_WALKTYPE_AUTH)
        {
          const char *repos_relpath =
            apr_pstrcat(iterpool,
                        apr_pstrmemdup(iterpool,
                                       ctx->repos_path->data,
                                       ctx->repos_path->len),
                        key, SVN_VA_NULL);
          if (! dav_svn__allow_read(ctx->info.r, ctx->info.repos,
                                    repos_relpath, ctx->info.root.rev,
                                    iterpool))
            continue;
        }

      /* append this child to our buffers */
      svn_stringbuf_appendbytes(ctx->info.uri_path, key, klen);
      svn_stringbuf_appendbytes(ctx->uri, key, klen);
      svn_stringbuf_appendbytes(ctx->repos_path, key, klen);

      /* reset the pointers since the above may have changed them */
      ctx->res.uri = ctx->uri->data;
      ctx->info.repos_path = ctx->repos_path->data;

      if (dirent->kind == svn_node_file)
        {
          err = (*params->func)(&ctx->wres, DAV_CALLTYPE_MEMBER);
          if (err != NULL)
            {
              svn_pool_destroy(iterpool);
              return err;
            }
        }
      else
        {
          /* this resource is a collection */
          ctx->res.collection = TRUE;

          /* append a slash to the URI (the path doesn't need it yet) */
          svn_stringbuf_appendcstr(ctx->uri, "/");
          ctx->res.uri = ctx->uri->data;

          /* recurse on this collection */
          err = do_walk(ctx, depth - 1, FALSE, iterpool);
          if (err != NULL)
            {
              svn_pool_destroy(iterpool);
              return err;
            }

          /* restore the data */
          ctx->res.collection = FALSE;
        }

      /* chop the child off the paths and uri. NOTE: no null-term. */
      ctx->info.uri_path->len = path_len;
      ctx->uri->len = uri_len;
      ctx->repos_path->len = repos_len;
    }

  svn_pool_destroy(iterpool);

  return NULL;
}

static dav_error *
walk(const dav_walk_params *params, int depth, dav_response **response)
{
  /* Thinking about adding support for LOCKNULL resources in this
     walker?  Check out the (working) code that was removed here:
          Author: cmpilato
          Date: Fri Mar 18 14:54:02 2005
          New Revision: 13475
     */

  walker_ctx_t ctx = { 0 };
  dav_error *err;

  if (params->root->info->restype == DAV_SVN_RESTYPE_PARENTPATH_COLLECTION)
    {
      /* Cannot walk an SVNParentPath collection, there is no repository. */
      return NULL;
    }

  ctx.params = params;

  ctx.wres.walk_ctx = params->walk_ctx;
  ctx.wres.pool = params->pool;
  ctx.wres.resource = &ctx.res;

  /* copy the resource over and adjust the "info" reference */
  ctx.res = *params->root;
  ctx.info = *ctx.res.info;

  ctx.res.info = &ctx.info;

  /* operate within the proper pool */
  ctx.res.pool = params->pool;

  /* Don't monkey with the path from params->root. Create a new one.
     This path will then be extended/shortened as necessary. */
  ctx.info.uri_path = svn_stringbuf_dup(ctx.info.uri_path, params->pool);

  /* prep the URI buffer */
  ctx.uri = svn_stringbuf_create(params->root->uri, params->pool);

  /* same for repos_path */
  if (ctx.info.repos_path == NULL)
    ctx.repos_path = NULL;
  else
    ctx.repos_path = svn_stringbuf_create(ctx.info.repos_path, params->pool);

  /* if we have a collection, then ensure the URI has a trailing "/" */
  /* ### get_resource always kills the trailing slash... */
  if (ctx.res.collection && ctx.uri->data[ctx.uri->len - 1] != '/') {
    svn_stringbuf_appendcstr(ctx.uri, "/");
  }

  /* the current resource's URI is stored in the (telescoping) ctx.uri */
  ctx.res.uri = ctx.uri->data;

  /* the current resource's repos_path is stored in ctx.repos_path */
  if (ctx.repos_path != NULL)
    ctx.info.repos_path = ctx.repos_path->data;

  /* ### is the root already/always open? need to verify */

  /* always return the error, and any/all multistatus responses */
  err = do_walk(&ctx, depth, TRUE, params->pool);
  *response = ctx.wres.response;

  return err;
}



/*** Utility functions for resource management ***/

dav_resource *
dav_svn__create_working_resource(dav_resource *base,
                                 const char *activity_id,
                                 const char *txn_name,
                                 int tweak_in_place)
{
  const char *path;
  dav_resource *res;

  if (base->baselined)
    path = apr_psprintf(base->pool,
                        "/%s/wbl/%s/%ld",
                        base->info->repos->special_uri,
                        activity_id, base->info->root.rev);
  else
    path = apr_psprintf(base->pool, "/%s/wrk/%s%s",
                        base->info->repos->special_uri,
                        activity_id, base->info->repos_path);
  path = svn_path_uri_encode(path, base->pool);

  if (tweak_in_place)
    res = base;
  else
    {
      res = apr_pcalloc(base->pool, sizeof(*res));
      res->info = apr_pcalloc(base->pool, sizeof(*res->info));
    }

  res->type = DAV_RESOURCE_TYPE_WORKING;
  res->exists = TRUE;      /* ### not necessarily correct */
  res->versioned = TRUE;
  res->working = TRUE;
  res->baselined = base->baselined;
  /* collection = FALSE.   ### not necessarily correct */

  if (base->info->repos->root_path[1])
    res->uri = apr_pstrcat(base->pool, base->info->repos->root_path,
                           path, SVN_VA_NULL);
  else
    res->uri = path;
  res->hooks = &dav_svn__hooks_repository;
  res->pool = base->pool;

  res->info->uri_path = svn_stringbuf_create(path, base->pool);
  res->info->repos = base->info->repos;
  res->info->repos_path = base->info->repos_path;
  res->info->root.rev = base->info->root.rev;
  res->info->root.activity_id = activity_id;
  res->info->root.txn_name = txn_name;

  if (tweak_in_place)
    return NULL;
  else
    return res;
}


dav_error *
dav_svn__working_to_regular_resource(dav_resource *resource)
{
  dav_resource_private *priv = resource->info;
  dav_svn_repos *repos = priv->repos;
  const char *path;
  svn_error_t *serr;

  /* no need to change the repos object or repos_path */

  /* set type back to REGULAR */
  resource->type = DAV_RESOURCE_TYPE_REGULAR;

  /* remove the working flag */
  resource->working = FALSE;

  /* Change the URL into either a baseline-collection or a public one. */
  if (priv->root.rev == SVN_INVALID_REVNUM)
    {
      serr = dav_svn__get_youngest_rev(&priv->root.rev, repos, resource->pool);
      if (serr != NULL)
        return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                    "Could not determine youngest rev.",
                                    resource->pool);

      /* create public URL */
      path = apr_psprintf(resource->pool, "%s", priv->repos_path);
    }
  else
    {
      /* if rev was specific, create baseline-collection URL */
      path = dav_svn__build_uri(repos, DAV_SVN__BUILD_URI_BC,
                                priv->root.rev, priv->repos_path,
                                FALSE /* add_href */, resource->pool);
    }
  path = svn_path_uri_encode(path, resource->pool);
  priv->uri_path = svn_stringbuf_create(path, resource->pool);

  /* change root.root back into a revision root. */
  serr = svn_fs_revision_root(&priv->root.root, repos->fs,
                              priv->root.rev, resource->pool);
  if (serr != NULL)
    return dav_svn__convert_err(serr, HTTP_INTERNAL_SERVER_ERROR,
                                "Could not open revision root.",
                                resource->pool);

  return NULL;
}


dav_error *
dav_svn__create_version_resource(dav_resource **version_res,
                                 const char *uri,
                                 apr_pool_t *pool)
{
  int result;
  dav_error *err;

  dav_resource_combined *comb = apr_pcalloc(pool, sizeof(*comb));

  result = parse_version_uri(comb, uri, NULL, 0);
  if (result != 0)
    return dav_svn__new_error(pool, HTTP_INTERNAL_SERVER_ERROR, 0, 0,
                              "Could not parse version resource uri.");

  err = prep_version(comb);
  if (err)
    return err;

  *version_res = &comb->res;
  return NULL;
}



static dav_error *
handle_post_request(request_rec *r,
                    dav_resource *resource,
                    dav_svn__output *output)
{
  svn_skel_t *request_skel, *post_skel;
  int status;
  apr_pool_t *pool = resource->pool;

  /* Make sure our skel-based request parses okay, has an initial atom
     that identifies what kind of action is expected, and that that
     action is something we understand.  */
  status = dav_svn__parse_request_skel(&request_skel, r, pool);

  if (status != OK)
    return dav_svn__new_error(pool, status, 0, 0,
                              "Error parsing skel POST request body.");

  if (svn_skel__list_length(request_skel) < 1)
    return dav_svn__new_error(pool, HTTP_BAD_REQUEST, 0, 0,
                              "Unable to identify skel POST request flavor.");

  post_skel = request_skel->children;

  /* NOTE: If you add POST handlers here, you'll want to advertise
     that the server supports them, too.  See version.c:get_option(). */

  if (svn_skel__matches_atom(post_skel, "create-txn"))
    {
      return dav_svn__post_create_txn(resource, request_skel, output);
    }
  else if (svn_skel__matches_atom(post_skel, "create-txn-with-props"))
    {
      return dav_svn__post_create_txn_with_props(resource,
                                                 request_skel, output);
    }

  return dav_svn__new_error(pool, HTTP_BAD_REQUEST, 0, 0,
                            "Unsupported skel POST request flavor.");
}


/* A stripped down version of mod_dav's dav_handle_err so that POST
   errors, which are not passed via mod_dav, are handled in the same
   way as errors for requests that are passed via mod_dav. */
static int
handle_err(request_rec *r, dav_error *err)
{
  dav_error *stackerr = err;

  dav_svn__log_err(r, err, APLOG_ERR);

  /* our error messages are safe; tell Apache this */
  apr_table_setn(r->notes, "verbose-error-to", "*");

  /* We might be able to generate a standard <D:error> response.
     Search the error stack for an errortag. */
  while (stackerr != NULL && stackerr->tagname == NULL)
    stackerr = stackerr->prev;

  if (stackerr != NULL && stackerr->tagname != NULL)
    return dav_svn__error_response_tag(r, stackerr);

  return err->status;
}


int dav_svn__method_post(request_rec *r)
{
  dav_resource *resource;
  dav_error *derr;
  const char *content_type;

  /* We only allow POSTs against the "me resource" right now. */
  derr = get_resource(r, dav_svn__get_root_dir(r),
                      "ignored", 0, &resource);
  if (derr != NULL)
    return derr->status;
  if (resource->info->restype != DAV_SVN_RESTYPE_ME)
    return HTTP_BAD_REQUEST;

  /* Pass skel-type POST request handling off to a dispatcher; any
     other type of request is considered bogus. */
  content_type = apr_table_get(r->headers_in, "content-type");
  if (content_type && (strcmp(content_type, SVN_SKEL_MIME_TYPE) == 0))
    {
      dav_svn__output *output = dav_svn__output_create(resource->info->r,
                                                       resource->pool);
      derr = handle_post_request(r, resource, output);
    }
  else
    {
      derr = dav_svn__new_error(resource->pool, HTTP_BAD_REQUEST, 0, 0,
                                "Unsupported POST request type.");
    }

  /* If something went wrong above, we'll generate a response back to
     the client with (hopefully) some helpful information. */
  if (derr)
    {
      /* POST is not a DAV method and so mod_dav isn't involved and
         won't handle this error.  Do it explicitly. */
      return handle_err(r, derr);
    }

  return OK;
}



const dav_hooks_repository dav_svn__hooks_repository =
{
  1,                            /* special GET handling */
  get_resource,
  get_parent_resource,
  is_same_resource,
  is_parent_resource,
  open_stream,
  close_stream,
  write_stream,
  seek_stream,
  set_headers,
  deliver,
  create_collection,
  copy_resource,
  move_resource,
  remove_resource,
  walk,
  getetag_pathetic
};
