ra_loader.c   [plain text]

/*
 * ra_loader.c:  logic for loading different RA library implementations
 *
 * ====================================================================
 * Copyright (c) 2000-2004 CollabNet.  All rights reserved.
 *
 * This software is licensed as described in the file COPYING, which
 * you should have received as part of this distribution.  The terms
 * are also available at http://subversion.tigris.org/license-1.html.
 * If newer versions of this license are posted there, you may use a
 * newer version instead, at your option.
 *
 * This software consists of voluntary contributions made by many
 * individuals.  For exact contribution history, see the revision
 * history and logs, available at http://subversion.tigris.org/.
 * ====================================================================
 */

/* ==================================================================== */

/*** Includes. ***/
#define APR_WANT_STRFUNC
#include <apr_want.h>

#include <apr.h>
#include <apr_strings.h>
#include <apr_pools.h>
#include <apr_hash.h>

#include "svn_version.h"
#include "svn_types.h"
#include "svn_error.h"
#include "svn_pools.h"
#include "svn_ra.h"
#include "svn_xml.h"
#include "svn_path.h"
#include "svn_dso.h"
#include "ra_loader.h"
#include "svn_private_config.h"


/* ### this file maps URL schemes to particular RA libraries. This is not
   ### entirely correct, as a single scheme could potentially be served
   ### by more than one loader. However, we can ignore that until we
   ### actually run into a conflict within the scheme portion of a URL. */


/* These are the URI schemes that the respective libraries *may* support.
 * The schemes actually supported may be a subset of the schemes listed below.
 * This can't be determine until the library is loaded.
 * (Currently, this applies to the https scheme of ra_dav, which is only
 * available if SSL is supported.) */
static const char * const dav_schemes[] = { "http", "https", NULL };
static const char * const svn_schemes[] = { "svn", NULL };
static const char * const local_schemes[] = { "file", NULL };

static const struct ra_lib_defn {
  /* the name of this RA library (e.g. "dav" or "local") */
  const char *ra_name;

  const char * const *schemes;
  /* the initialization function if linked in; otherwise, NULL */
  svn_ra__init_func_t initfunc;
  svn_ra_init_func_t compat_initfunc;
} ra_libraries[] = {
  {
    "dav",
    dav_schemes,
#ifdef SVN_LIBSVN_CLIENT_LINKS_RA_DAV
    svn_ra_dav__init,
    svn_ra_dav_init
#endif
  },

  {
    "svn",
    svn_schemes,
#ifdef SVN_LIBSVN_CLIENT_LINKS_RA_SVN
    svn_ra_svn__init,
    svn_ra_svn_init
#endif
  },

  {
    "local",
    local_schemes,
#ifdef SVN_LIBSVN_CLIENT_LINKS_RA_LOCAL
    svn_ra_local__init,
    svn_ra_local_init
#endif
  },

  {
    "serf",
    dav_schemes,
#ifdef SVN_LIBSVN_CLIENT_LINKS_RA_SERF
    svn_ra_serf__init,
    svn_ra_serf_init
#endif
  },

  /* ADD NEW RA IMPLEMENTATIONS HERE (as they're written) */

  /* sentinel */
  { NULL }
};

/* Ensure that the RA library NAME is loaded.
 *
 * If FUNC is non-NULL, set *FUNC to the address of the svn_ra_NAME__init
 * function of the library.
 *
 * If COMPAT_FUNC is non-NULL, set *COMPAT_FUNC to the address of the
 * svn_ra_NAME_init compatibility init function of the library.
 *
 * ### todo: Any RA libraries implemented from this point forward
 * ### don't really need an svn_ra_NAME_init compatibility function.
 * ### Currently, load_ra_module() will error if no such function is
 * ### found, but it might be more friendly to simply set *COMPAT_FUNC
 * ### to null (assuming COMPAT_FUNC itself is non-null).
 */
static svn_error_t *
load_ra_module(svn_ra__init_func_t *func,
               svn_ra_init_func_t *compat_func,
               const char *ra_name, apr_pool_t *pool)
{
  if (func)
    *func = NULL;
  if (compat_func)
    *compat_func = NULL;

#if APR_HAS_DSO
  {
    apr_dso_handle_t *dso;
    apr_dso_handle_sym_t symbol;
    const char *libname;
    const char *funcname;
    const char *compat_funcname;
    apr_status_t status;

    libname = apr_psprintf(pool, "libsvn_ra_%s-%d.so.0",
                           ra_name, SVN_VER_MAJOR);
    funcname = apr_psprintf(pool, "svn_ra_%s__init", ra_name);
    compat_funcname = apr_psprintf(pool, "svn_ra_%s_init", ra_name);

    /* find/load the specified library */
    SVN_ERR(svn_dso_load(&dso, libname));
    if (! dso)
      return SVN_NO_ERROR;

    /* find the initialization routines */
    if (func)
      {
        status = apr_dso_sym(&symbol, dso, funcname);
        if (status)
          {
            return svn_error_wrap_apr(status,
                                      _("'%s' does not define '%s()'"),
                                      libname, funcname);
          }

        *func = (svn_ra__init_func_t) symbol;
      }

    if (compat_func)
      {
        status = apr_dso_sym(&symbol, dso, compat_funcname);
        if (status)
          {
            return svn_error_wrap_apr(status,
                                      _("'%s' does not define '%s()'"),
                                      libname, compat_funcname);
          }

        *compat_func = (svn_ra_init_func_t) symbol;
      }
  }
#endif /* APR_HAS_DSO */

  return SVN_NO_ERROR;
}

/* If DEFN may support URL, return the scheme.  Else, return NULL. */
static const char *
has_scheme_of(const struct ra_lib_defn *defn, const char *url)
{
  const char * const *schemes;
  apr_size_t len;

  for (schemes = defn->schemes; *schemes != NULL; ++schemes)
    {
      const char *scheme = *schemes;
      len = strlen(scheme);
      /* Case-insensitive comparison, per RFC 2396 section 3.1.  Allow
         URL to contain a trailing "+foo" section in the scheme, since
         that's how we specify tunnel schemes in ra_svn. */
      if (strncasecmp(scheme, url, len) == 0 &&
          (url[len] == ':' || url[len] == '+'))
        return scheme;
    }

  return NULL;
}

/* Return an error if RA_VERSION doesn't match the version of this library.
   Use SCHEME in the error message to describe the library that was loaded. */
static svn_error_t *
check_ra_version(const svn_version_t *ra_version, const char *scheme)
{
  const svn_version_t *my_version = svn_ra_version();
  if (!svn_ver_equal(my_version, ra_version))
    return svn_error_createf(SVN_ERR_VERSION_MISMATCH, NULL,
                             _("Mismatched RA version for '%s':"
                               " found %d.%d.%d%s,"
                               " expected %d.%d.%d%s"),
                             scheme,
                             my_version->major, my_version->minor,
                             my_version->patch, my_version->tag,
                             ra_version->major, ra_version->minor,
                             ra_version->patch, ra_version->tag);

  return SVN_NO_ERROR;
}

/* -------------------------------------------------------------- */

/*** Public Interfaces ***/

svn_error_t *svn_ra_initialize(apr_pool_t *pool)
{
  return SVN_NO_ERROR;
}

/* Please note: the implementation of svn_ra_create_callbacks is
 * duplicated in libsvn_ra/wrapper_template.h:compat_open() .  This
 * duplication is intentional, is there to avoid a circular
 * dependancy, and is justified in great length in the code of
 * compat_open() in libsvn_ra/wrapper_template.h.  If you modify the
 * implementation of svn_ra_create_callbacks(), be sure to keep the
 * code in wrapper_template.h:compat_open() in sync with your
 * changes. */
svn_error_t *
svn_ra_create_callbacks(svn_ra_callbacks2_t **callbacks,
                        apr_pool_t *pool)
{
  *callbacks = apr_pcalloc(pool, sizeof(**callbacks));
  return SVN_NO_ERROR;
}

svn_error_t *svn_ra_open2(svn_ra_session_t **session_p,
                          const char *repos_URL,
                          const svn_ra_callbacks2_t *callbacks,
                          void *callback_baton,
                          apr_hash_t *config,
                          apr_pool_t *pool)
{
  svn_ra_session_t *session;
  const struct ra_lib_defn *defn;
  const svn_ra__vtable_t *vtable = NULL;

  /* Find the library. */
  for (defn = ra_libraries; defn->ra_name != NULL; ++defn)
    {
      const char *scheme;

      if ((scheme = has_scheme_of(defn, repos_URL)))
        {
          svn_ra__init_func_t initfunc = defn->initfunc;

          if (! initfunc)
            SVN_ERR(load_ra_module(&initfunc, NULL, defn->ra_name,
                                   pool));
          if (! initfunc)
            /* Library not found. */
            continue;

          SVN_ERR(initfunc(svn_ra_version(), &vtable, pool));

          SVN_ERR(check_ra_version(vtable->get_version(), scheme));
        }
    }
    
  if (vtable == NULL)
    return svn_error_createf(SVN_ERR_RA_ILLEGAL_URL, NULL,
                             _("Unrecognized URL scheme for '%s'"),
                             repos_URL);

  /* Create the session object. */
  session = apr_pcalloc(pool, sizeof(*session));
  session->vtable = vtable;
  session->pool = pool;

  /* Ask the library to open the session. */
  SVN_ERR(vtable->open(session, repos_URL, callbacks, callback_baton,
                       config, pool));

  *session_p = session;
  return SVN_NO_ERROR;
}

svn_error_t *svn_ra_open(svn_ra_session_t **session_p,
                         const char *repos_URL,
                         const svn_ra_callbacks_t *callbacks,
                         void *callback_baton,
                         apr_hash_t *config,
                         apr_pool_t *pool)
{
  /* Deprecated function. Copy the contents of the svn_ra_callbacks_t
     to a new svn_ra_callbacks2_t and call svn_ra_open2(). */
  svn_ra_callbacks2_t *callbacks2;
  SVN_ERR(svn_ra_create_callbacks(&callbacks2, pool));
  callbacks2->open_tmp_file = callbacks->open_tmp_file;
  callbacks2->auth_baton = callbacks->auth_baton;
  callbacks2->get_wc_prop = callbacks->get_wc_prop;
  callbacks2->set_wc_prop = callbacks->set_wc_prop;
  callbacks2->push_wc_prop = callbacks->push_wc_prop;
  callbacks2->invalidate_wc_props = callbacks->invalidate_wc_props;
  callbacks2->progress_func = NULL;
  callbacks2->progress_baton = NULL;
  return svn_ra_open2(session_p, repos_URL,
                      callbacks2, callback_baton,
                      config, pool);
}

svn_error_t *svn_ra_reparent(svn_ra_session_t *session,
                             const char *url,
                             apr_pool_t *pool)
{
  const char *repos_root;

  /* Make sure the new URL is in the same repository, so that the
     implementations don't have to do it. */
  SVN_ERR(svn_ra_get_repos_root(session, &repos_root, pool));
  if (! svn_path_is_ancestor(repos_root, url))
    return svn_error_createf(SVN_ERR_RA_ILLEGAL_URL, NULL,
                             _("'%s' isn't in the same repository as '%s'"),
                             url, repos_root);

  return session->vtable->reparent(session, url, pool);
}

svn_error_t *svn_ra_get_latest_revnum(svn_ra_session_t *session,
                                      svn_revnum_t *latest_revnum,
                                      apr_pool_t *pool)
{
  return session->vtable->get_latest_revnum(session, latest_revnum, pool);
}

svn_error_t *svn_ra_get_dated_revision(svn_ra_session_t *session,
                                       svn_revnum_t *revision,
                                       apr_time_t tm,
                                       apr_pool_t *pool)
{
  return session->vtable->get_dated_revision(session, revision, tm, pool);
}

svn_error_t *svn_ra_change_rev_prop(svn_ra_session_t *session,
                                    svn_revnum_t rev,
                                    const char *name,
                                    const svn_string_t *value,
                                    apr_pool_t *pool)
{
  return session->vtable->change_rev_prop(session, rev, name, value, pool);
}

svn_error_t *svn_ra_rev_proplist(svn_ra_session_t *session,
                                 svn_revnum_t rev,
                                 apr_hash_t **props,
                                 apr_pool_t *pool)
{
  return session->vtable->rev_proplist(session, rev, props, pool);
}

svn_error_t *svn_ra_rev_prop(svn_ra_session_t *session,
                             svn_revnum_t rev,
                             const char *name,
                             svn_string_t **value,
                             apr_pool_t *pool)
{
  return session->vtable->rev_prop(session, rev, name, value, pool);
}

svn_error_t *svn_ra_get_commit_editor2(svn_ra_session_t *session,
                                       const svn_delta_editor_t **editor,
                                       void **edit_baton,
                                       const char *log_msg,
                                       svn_commit_callback2_t callback,
                                       void *callback_baton,
                                       apr_hash_t *lock_tokens,
                                       svn_boolean_t keep_locks,
                                       apr_pool_t *pool)
{
  return session->vtable->get_commit_editor(session, editor, edit_baton,
                                            log_msg, callback, callback_baton,
                                            lock_tokens, keep_locks, pool);
}

svn_error_t *svn_ra_get_commit_editor(svn_ra_session_t *session,
                                      const svn_delta_editor_t **editor,
                                      void **edit_baton,
                                      const char *log_msg,
                                      svn_commit_callback_t callback,
                                      void *callback_baton,
                                      apr_hash_t *lock_tokens,
                                      svn_boolean_t keep_locks,
                                      apr_pool_t *pool)
{
  svn_commit_callback2_t callback2;
  void *callback2_baton;

  svn_compat_wrap_commit_callback(&callback2, &callback2_baton,
                                  callback, callback_baton,
                                  pool);

  return svn_ra_get_commit_editor2(session, editor, edit_baton,
                                   log_msg, callback2,
                                   callback2_baton, lock_tokens,
                                   keep_locks, pool);
}

svn_error_t *svn_ra_get_file(svn_ra_session_t *session,
                             const char *path,
                             svn_revnum_t revision,
                             svn_stream_t *stream,
                             svn_revnum_t *fetched_rev,
                             apr_hash_t **props,
                             apr_pool_t *pool)
{
  return session->vtable->get_file(session, path, revision, stream,
                                   fetched_rev, props, pool);
}

svn_error_t *svn_ra_get_dir(svn_ra_session_t *session,
                            const char *path,
                            svn_revnum_t revision,
                            apr_hash_t **dirents,
                            svn_revnum_t *fetched_rev,
                            apr_hash_t **props,
                            apr_pool_t *pool)
{
  return session->vtable->get_dir(session, dirents, fetched_rev, props,
                                  path, revision, SVN_DIRENT_ALL, pool);
}

svn_error_t *svn_ra_get_dir2(svn_ra_session_t *session,
                             apr_hash_t **dirents,
                             svn_revnum_t *fetched_rev,
                             apr_hash_t **props,
                             const char *path,
                             svn_revnum_t revision,
                             apr_uint32_t dirent_fields,
                             apr_pool_t *pool)
{
  return session->vtable->get_dir(session, dirents, fetched_rev, props,
                                  path, revision, dirent_fields, pool);
}

svn_error_t *svn_ra_do_update(svn_ra_session_t *session,
                              const svn_ra_reporter2_t **reporter,
                              void **report_baton,
                              svn_revnum_t revision_to_update_to,
                              const char *update_target,
                              svn_boolean_t recurse,
                              const svn_delta_editor_t *update_editor,
                              void *update_baton,
                              apr_pool_t *pool)
{
  return session->vtable->do_update(session, reporter, report_baton,
                                    revision_to_update_to, update_target,
                                    recurse, update_editor, update_baton,
                                    pool);
}

svn_error_t *svn_ra_do_switch(svn_ra_session_t *session,
                              const svn_ra_reporter2_t **reporter,
                              void **report_baton,
                              svn_revnum_t revision_to_switch_to,
                              const char *switch_target,
                              svn_boolean_t recurse,
                              const char *switch_url,
                              const svn_delta_editor_t *switch_editor,
                              void *switch_baton,
                              apr_pool_t *pool)
{
  return session->vtable->do_switch(session, reporter, report_baton,
                                    revision_to_switch_to, switch_target,
                                    recurse, switch_url, switch_editor,
                                    switch_baton, pool);
}

svn_error_t *svn_ra_do_status(svn_ra_session_t *session,
                              const svn_ra_reporter2_t **reporter,
                              void **report_baton,
                              const char *status_target,
                              svn_revnum_t revision,
                              svn_boolean_t recurse,
                              const svn_delta_editor_t *status_editor,
                              void *status_baton,
                              apr_pool_t *pool)
{
  return session->vtable->do_status(session, reporter, report_baton,
                                    status_target, revision, recurse,
                                    status_editor, status_baton, pool);
}

svn_error_t *svn_ra_do_diff2(svn_ra_session_t *session,
                             const svn_ra_reporter2_t **reporter,
                             void **report_baton,
                             svn_revnum_t revision,
                             const char *diff_target,
                             svn_boolean_t recurse,
                             svn_boolean_t ignore_ancestry,
                             svn_boolean_t text_deltas,
                             const char *versus_url,
                             const svn_delta_editor_t *diff_editor,
                             void *diff_baton,
                             apr_pool_t *pool)
{
  return session->vtable->do_diff(session, reporter, report_baton, revision,
                                  diff_target, recurse, ignore_ancestry,
                                  text_deltas, versus_url, diff_editor,
                                  diff_baton, pool);
}

svn_error_t *svn_ra_do_diff(svn_ra_session_t *session,
                            const svn_ra_reporter2_t **reporter,
                            void **report_baton,
                            svn_revnum_t revision,
                            const char *diff_target,
                            svn_boolean_t recurse,
                            svn_boolean_t ignore_ancestry,
                            const char *versus_url,
                            const svn_delta_editor_t *diff_editor,
                            void *diff_baton,
                            apr_pool_t *pool)
{
  return svn_ra_do_diff2(session, reporter, report_baton, revision,
                         diff_target, recurse, ignore_ancestry, TRUE,
                         versus_url, diff_editor, diff_baton, pool);
}

svn_error_t *svn_ra_get_log(svn_ra_session_t *session,
                            const apr_array_header_t *paths,
                            svn_revnum_t start,
                            svn_revnum_t end,
                            int limit,
                            svn_boolean_t discover_changed_paths,
                            svn_boolean_t strict_node_history,
                            svn_log_message_receiver_t receiver,
                            void *receiver_baton,
                            apr_pool_t *pool)
{
  return session->vtable->get_log(session, paths, start, end, limit,
                                  discover_changed_paths, strict_node_history,
                                  receiver, receiver_baton, pool);
}

svn_error_t *svn_ra_check_path(svn_ra_session_t *session,
                               const char *path,
                               svn_revnum_t revision,
                               svn_node_kind_t *kind,
                               apr_pool_t *pool)
{
  return session->vtable->check_path(session, path, revision, kind, pool);
}

svn_error_t *svn_ra_stat(svn_ra_session_t *session,
                         const char *path,
                         svn_revnum_t revision,
                         svn_dirent_t **dirent,
                         apr_pool_t *pool)
{
  return session->vtable->stat(session, path, revision, dirent, pool);
}

svn_error_t *svn_ra_get_uuid(svn_ra_session_t *session,
                             const char **uuid,
                             apr_pool_t *pool)
{
  return session->vtable->get_uuid(session, uuid, pool);
}

svn_error_t *svn_ra_get_repos_root(svn_ra_session_t *session,
                                   const char **url,
                                   apr_pool_t *pool)
{
  return session->vtable->get_repos_root(session, url, pool);
}

svn_error_t *svn_ra_get_locations(svn_ra_session_t *session,
                                  apr_hash_t **locations,
                                  const char *path,
                                  svn_revnum_t peg_revision,
                                  apr_array_header_t *location_revisions,
                                  apr_pool_t *pool)
{
  return session->vtable->get_locations(session, locations, path,
                                        peg_revision, location_revisions,
                                        pool);
}

svn_error_t *svn_ra_get_file_revs(svn_ra_session_t *session,
                                  const char *path,
                                  svn_revnum_t start,
                                  svn_revnum_t end,
                                  svn_ra_file_rev_handler_t handler,
                                  void *handler_baton,
                                  apr_pool_t *pool)
{
  return session->vtable->get_file_revs(session, path, start, end, handler,
                                        handler_baton, pool);
}

svn_error_t *svn_ra_lock(svn_ra_session_t *session,
                         apr_hash_t *path_revs,
                         const char *comment,
                         svn_boolean_t steal_lock,
                         svn_ra_lock_callback_t lock_func, 
                         void *lock_baton,
                         apr_pool_t *pool)
{
  if (comment && ! svn_xml_is_xml_safe(comment, strlen(comment)))
    return svn_error_create
      (SVN_ERR_XML_UNESCAPABLE_DATA, NULL,
       _("Lock comment has illegal characters"));
  
  return session->vtable->lock(session, path_revs, comment, steal_lock,
                               lock_func, lock_baton, pool);
}

svn_error_t *svn_ra_unlock(svn_ra_session_t *session,
                           apr_hash_t *path_tokens,
                           svn_boolean_t break_lock,
                           svn_ra_lock_callback_t lock_func, 
                           void *lock_baton,
                           apr_pool_t *pool)
{
  return session->vtable->unlock(session, path_tokens, break_lock,
                                 lock_func, lock_baton, pool);
}

svn_error_t *svn_ra_get_lock(svn_ra_session_t *session,
                             svn_lock_t **lock,
                             const char *path,
                             apr_pool_t *pool)
{
  return session->vtable->get_lock(session, lock, path, pool);
}

svn_error_t *svn_ra_get_locks(svn_ra_session_t *session,
                              apr_hash_t **locks,
                              const char *path,
                              apr_pool_t *pool)
{
  return session->vtable->get_locks(session, locks, path, pool);
}

svn_error_t *svn_ra_replay(svn_ra_session_t *session,
                           svn_revnum_t revision,
                           svn_revnum_t low_water_mark,
                           svn_boolean_t text_deltas,
                           const svn_delta_editor_t *editor,
                           void *edit_baton,
                           apr_pool_t *pool)
{
  return session->vtable->replay(session, revision, low_water_mark,
                                 text_deltas, editor, edit_baton, pool);
}



svn_error_t *
svn_ra_print_modules(svn_stringbuf_t *output,
                     apr_pool_t *pool)
{
  const struct ra_lib_defn *defn;
  const char * const *schemes;
  svn_ra__init_func_t initfunc;
  const svn_ra__vtable_t *vtable;
  apr_pool_t *iterpool = svn_pool_create(pool);

  for (defn = ra_libraries; defn->ra_name != NULL; ++defn)
    {
      char *line;

      svn_pool_clear(iterpool);

      initfunc = defn->initfunc;
      if (! initfunc)
        SVN_ERR(load_ra_module(&initfunc, NULL, defn->ra_name,
                               iterpool));

      if (initfunc)
        {
          SVN_ERR(initfunc(svn_ra_version(), &vtable, iterpool));

          SVN_ERR(check_ra_version(vtable->get_version(), defn->ra_name));

          line = apr_psprintf(iterpool, "* ra_%s : %s\n",
                              defn->ra_name,
                              vtable->get_description());
          svn_stringbuf_appendcstr(output, line);

          for (schemes = vtable->get_schemes(iterpool); *schemes != NULL;
               ++schemes)
            {
              line = apr_psprintf(iterpool, _("  - handles '%s' scheme\n"),
                                  *schemes);
              svn_stringbuf_appendcstr(output, line);
            }
        }
    }

  svn_pool_destroy(iterpool);

  return SVN_NO_ERROR;
}


svn_error_t *
svn_ra_print_ra_libraries(svn_stringbuf_t **descriptions,
                          void *ra_baton,
                          apr_pool_t *pool)
{
  *descriptions = svn_stringbuf_create("", pool);
  return svn_ra_print_modules(*descriptions, pool);
}


/* Return the library version number. */
const svn_version_t *
svn_ra_version(void)
{
  SVN_VERSION_BODY;
}


/*** Compatibility Interfaces **/
svn_error_t *
svn_ra_init_ra_libs(void **ra_baton,
                    apr_pool_t *pool)
{
  *ra_baton = pool;
  return SVN_NO_ERROR;
}

svn_error_t *
svn_ra_get_ra_library(svn_ra_plugin_t **library,
                      void *ra_baton,
                      const char *url,
                      apr_pool_t *pool)
{
  const struct ra_lib_defn *defn;
  apr_pool_t *load_pool = ra_baton;
  apr_hash_t *ht = apr_hash_make(pool);

  /* Figure out which RA library key matches URL. */
  for (defn = ra_libraries; defn->ra_name != NULL; ++defn)
    {
      const char *scheme;
      if ((scheme = has_scheme_of(defn, url)))
        {
          svn_ra_init_func_t compat_initfunc = defn->compat_initfunc;

          if (! compat_initfunc)
            {
              SVN_ERR(load_ra_module
                      (NULL, &compat_initfunc, defn->ra_name, load_pool));
            }
          if (! compat_initfunc)
            {
              continue;
            }

          SVN_ERR(compat_initfunc(SVN_RA_ABI_VERSION, load_pool, ht));

          *library = apr_hash_get(ht, scheme, APR_HASH_KEY_STRING);

          /* The library may support just a subset of the schemes listed,
             so we have to check here too. */
          if (! *library)
            break;

          SVN_ERR(check_ra_version((*library)->get_version(), scheme));

          return SVN_NO_ERROR;
        }
    }
    
  /* Couldn't find a match... */
  *library = NULL;
  return svn_error_createf(SVN_ERR_RA_ILLEGAL_URL, NULL,
                           _("Unrecognized URL scheme '%s'"), url);
}