ConnectionCache.cxx

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/*
 * Copyright (c) 2004, The EROS Group, LLC and Johns Hopkins
 * University. All rights reserved.
 * 
 * This software was developed to support the EROS secure operating
 * system project (http://www.eros-os.org). The latest version of
 * the OpenCM software can be found at http://www.opencm.org.
 * 
 * Redistribution and use in source and binary forms, with or
 * without modification, are permitted provided that the following
 * conditions are met:
 * 
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 
 * 2. Redistributions in binary form must reproduce the above
 *    copyright notice, this list of conditions and the following
 *    disclaimer in the documentation and/or other materials
 *    provided with the distribution.
 * 
 * 3. Neither the name of the The EROS Group, LLC nor the name of
 *    Johns Hopkins University, nor the names of its contributors
 *    may be used to endorse or promote products derived from this
 *    software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
 * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include <repos/ConnectionCache.hxx>
#include <util/avl.hxx>

ConnectionCache ConnectionCache::theCache;

#ifdef NEED_CONVERT
/* A ConnectNode represents a connection to a repository. It maps a
   repos URI to both a "wrapped" repository and "unwrapped"
   repository.  Users connect to "wrapped" and "unwrapped"
   repositories in different circumstances.  For example, end users
   usually connect to an underlying (unwrapped) repository that's
   wrapped in an authrepos in order to support access checks to
   repository contents. Another example is that end users typically
   use a cacherepos in conjunction with a remote repository, so the
   (unwrapped) remote repository is wrapped in a cacherepos.  On the
   other hand, the client code must connect directly to an unwrapped
   cacherepos (using the anonymous user) in order to properly wrap a
   net repository for an end user.  Thus, the ConnectNode provides
   easy access to both the wrapped and unwrapped repositories for a
   given uri.  Note that for any given ConnectNode, the wrapped
   repository can be NULL, but the unwrapped repository will never be
   NULL. */

/* Implementation of the repository connection cache. */
#if 0
typedef struct ConnectNode ConnectNode;
struct ConnectNode {
  AvlNode avl;
  const char *uri;
  Repository *wrapped;
  Repository *unwrapped;
};

struct ConnectionCache {
  AvlTree *tree;
};
#endif

/* Comparator function.  */
static int
cnode_uri_cmp(AvlNode *n1, AvlNode *n2)
{
  ConnectNode *cn1 = (ConnectNode *)n1;
  ConnectNode *cn2 = (ConnectNode *)n2;

  /* Note that hashes don't buy us anything.  We really need the
  output of strcmp() in order to do the "greatest string less than or
  equal to" function */
  return strcmp(cn1->uri, cn2->uri);
}

ConnectionCache *
ccache_create(void)
{
  ConnectionCache *cache = GC_MALLOC(sizeof(ConnectionCache));
  cache->tree = avl_create(cnode_uri_cmp, gc_malloc);

  return cache;
}

static ConnectNode *
ccache_lookup(ConnectionCache *c, URI *uri)
{
  ConnectNode cn;
  ConnectNode *retNode;
  AvlNode *node = NULL;

  memset(&cn, 0, sizeof(cn));
  cn.uri = uri_toString(uri);

  /* This call returns the greatest key less than or equal to the
     search key */
  node = avl_lookupGLE(c->tree, (AvlNode *)(&cn));
  if (node == NULL)
    return NULL;

  /* Make sure the returned node's string is a prefix of the search
  string.  This filters out pseudo-matches like
  "file://joe@somewhere..." and "file://betty@elsewhere..." where the
  only really match is the uri scheme. */
  retNode = (ConnectNode *)node;
  if (path_isprefix(retNode->uri, cn.uri))
    return retNode;

  /* Else no match */
  return NULL;
}

static void 
ccache_insert(ConnectionCache *c, URI *key, 
              Repository *wrapped, Repository *unwrapped)
{
  ConnectNode *exists = ccache_lookup(c, key);

  if (exists)
    return;

  {
    ConnectNode *newNode = GC_NEW(ConnectNode);

    newNode->uri = uri_toString(key);
    newNode->wrapped = wrapped;
    newNode->unwrapped = unwrapped;
    avl_insert(c->tree, (AvlNode *)newNode);
  }
}

/* An iterator used to disconnect from the repositories in the
   connection cache. */
static int
ccache_disconnect(AvlNode *node)
{
  ConnectNode *cd = (ConnectNode *)node;

  /* Calling disconnect on the wrapper should disconnect everything
  underneath.  If no "wrapped", then disconnect the "unwrapped"
  repository directly. Repository might already be disconnected, so
  catch exceptions. */
  TRY {
    if (cd->wrapped)
      repos_Disconnect(cd->wrapped);
    else
      repos_Disconnect(cd->unwrapped);
  }
  DEFAULT(AnyException) {
  }
  END_CATCH;

  return 0;
}

void
ccache_destroy(ConnectionCache *c)
{
  if (c) {

    /* Disconnect every repository in the cache */
    avl_iterate(c->tree, ccache_disconnect);

    /* Set var to NULL so it will be GC'ed */
    c = NULL;
  }
}
#endif /* NEED_CONVERT */

GCPtr<Repository>
ConnectionCache::doGetRepository(GCPtr<URI> uri)
{
  assert(false);
}

GCPtr<Repository>
ConnectionCache::doGetUnwrappedRepository(GCPtr<URI> uri)
{
  assert(false);
}

#ifdef NEED_CONVERT
/* Return a connected repository, either wrapped or unwrapped
depending on what was resolved or found in the connection cache.  If
there is a corresponding wrapped repository, return that in favor of
the unwrapped.  In some cases, like the creation of an underlying
cache repository, there won't be a wrapper repository.  In those
cases, return the unwrapped, connected repository. */
Repository *
ccache_get_repository(ConnectionCache *c, URI *uri)
{
  URI *key = NULL;

  if (!c)
    THROW(ExNullArg, format("NULL connection cache encountered."));

  /* See if there's already a connection for this uri */
  ConnectNode *cnode = ccache_lookup(c, uri);
  if (cnode == NULL) {

    /* Open and connect to specified repository */
    Repository *wrapped = NULL;
    Repository *unwrapped = repository_open(uri);
    repos_Connect(unwrapped);

    /* Wrapping logic: for all repositories that need it wrap
       appropriately with an authRepos, cacheRepos, or both. */
    if (REPOS_NEEDS_AUTHWRAP(unwrapped))
      wrapped = authrepository_wrap(unwrapped);

    if (REPOS_IS_REMOTE(unwrapped))
      wrapped = cacherepository_wrap(unwrapped);

    if (wrapped)
      key = wrapped->uri;
    else
      key = unwrapped->uri;

    ccache_insert(c, key, wrapped, unwrapped);

    return wrapped ? wrapped : unwrapped;
   } 
  else {
    if (cnode->wrapped == NULL)
      return cnode->unwrapped;
    else
      return cnode->wrapped;
  }

  THROW(ExNoObject, format("Couldn't get repository for \"%s\".", uri->URI));

  return NULL;
}

/* This call is the exception rather than the rule.  Use this when the
caller specifically needs the unwrapped connection, even if there
exists a wrapped connection.  Example:  "cm admin gc" wants to do the
gc on the underlying (unwrapped) repository. */
Repository *
ccache_get_unwrapped_repository(ConnectionCache *c, URI *uri)
{
  /* See if there's already a connection for this uri */
  ConnectNode *cnode = ccache_lookup(c, uri);
  if (cnode == NULL) {

    /* Open and connect to specified repository */
    Repository *unwrapped = repository_open(uri);
    repos_Connect(unwrapped);

    /* Skip the wrapping logic and insert this one without a wrapper */
    ccache_insert(c, unwrapped->uri, NULL, unwrapped);
    return unwrapped;
   } 
  else {
    return cnode->unwrapped;
  }

  THROW(ExNoObject, format("Couldn't get repository for \"%s\".", uri->URI));

  return NULL;
}

#endif /* NEED_CONVERT */

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