src/TortoiseMerge/libsvn_diff/dso.c

   1 /*
   2  * ====================================================================
   3  * Copyright (c) 2006 CollabNet.  All rights reserved.
   4  *
   5  * This software is licensed as described in the file COPYING, which
   6  * you should have received as part of this distribution.  The terms
   7  * are also available at http://subversion.tigris.org/license-1.html.
   8  * If newer versions of this license are posted there, you may use a
   9  * newer version instead, at your option.
  10  *
  11  * This software consists of voluntary contributions made by many
  12  * individuals.  For exact contribution history, see the revision
  13  * history and logs, available at http://subversion.tigris.org/.
  14  * ====================================================================
  15  */
  16
  17 #include <apr_thread_mutex.h>
  18 #include <apr_hash.h>
  19
  20 #include "svn_dso.h"
  21 #include "svn_pools.h"
  22 //#include "svn_private_config.h"
  23
  24 /* A mutex to protect our global pool and cache. */
  25 #if APR_HAS_THREADS
  26 static apr_thread_mutex_t *dso_mutex;
  27 #endif
  28
  29 /* Global pool to allocate DSOs in. */
  30 static apr_pool_t *dso_pool;
  31
  32 /* Global cache for storing DSO objects. */
  33 static apr_hash_t *dso_cache;
  34
  35 /* Just an arbitrary location in memory... */
  36 static int not_there_sentinel;
  37
  38 /* A specific value we store in the dso_cache to indicate that the
  39    library wasn't found.  This keeps us from allocating extra memory
  40    from dso_pool when trying to find libraries we already know aren't
  41    there.  */
  42 #define NOT_THERE ((void *) &not_there_sentinel)
  43
  44 svn_error_t *
  45 svn_dso_initialize2(void)
  46 {
  47   apr_status_t status;
  48   if (dso_pool)
  49     return SVN_NO_ERROR;
  50
  51   dso_pool = svn_pool_create(NULL);
  52
  53 #if APR_HAS_THREADS
  54   status = apr_thread_mutex_create(&dso_mutex,
  55                                    APR_THREAD_MUTEX_DEFAULT, dso_pool);
  56   if (status)
  57     return svn_error_wrap_apr(status, _("Can't create DSO mutex"));
  58 #endif
  59
  60   dso_cache = apr_hash_make(dso_pool);
  61   return SVN_NO_ERROR;
  62 }
  63
  64 #if APR_HAS_DSO
  65 svn_error_t *
  66 svn_dso_load(apr_dso_handle_t **dso, const char *fname)
  67 {
  68   apr_status_t status;
  69
  70   if (! dso_pool)
  71     SVN_ERR(svn_dso_initialize2());
  72
  73 #if APR_HAS_THREADS
  74   status = apr_thread_mutex_lock(dso_mutex);
  75   if (status)
  76     return svn_error_wrap_apr(status, _("Can't grab DSO mutex"));
  77 #endif
  78
  79   *dso = apr_hash_get(dso_cache, fname, APR_HASH_KEY_STRING);
  80
  81   /* First check to see if we've been through this before...  We do this
  82      to avoid calling apr_dso_load multiple times for a given library,
  83      which would result in wasting small amounts of memory each time. */
  84   if (*dso == NOT_THERE)
  85     {
  86       *dso = NULL;
  87 #if APR_HAS_THREADS
  88       status = apr_thread_mutex_unlock(dso_mutex);
  89       if (status)
  90         return svn_error_wrap_apr(status, _("Can't ungrab DSO mutex"));
  91 #endif
  92       return SVN_NO_ERROR;
  93     }
  94
  95   /* If we got nothing back from the cache, try and load the library. */
  96   if (! *dso)
  97     {
  98       status = apr_dso_load(dso, fname, dso_pool);
  99       if (status)
 100         {
 101           *dso = NULL;
 102
 103           /* It wasn't found, so set the special "we didn't find it" value. */
 104           apr_hash_set(dso_cache,
 105                        apr_pstrdup(dso_pool, fname),
 106                        APR_HASH_KEY_STRING,
 107                        NOT_THERE);
 108
 109 #if APR_HAS_THREADS
 110           status = apr_thread_mutex_unlock(dso_mutex);
 111           if (status)
 112             return svn_error_wrap_apr(status, _("Can't ungrab DSO mutex"));
 113 #endif
 114           return SVN_NO_ERROR;
 115         }
 116
 117       /* Stash the dso so we can use it next time. */
 118       apr_hash_set(dso_cache,
 119                    apr_pstrdup(dso_pool, fname),
 120                    APR_HASH_KEY_STRING,
 121                    *dso);
 122     }
 123
 124 #if APR_HAS_THREADS
 125   status = apr_thread_mutex_unlock(dso_mutex);
 126   if (status)
 127     return svn_error_wrap_apr(status, _("Can't ungrab DSO mutex"));
 128 #endif
 129
 130   return SVN_NO_ERROR;
 131 }
 132 #endif /* APR_HAS_DSO */