xdgmime: Finer handling for cases where mmap() is not available

`mmap()` is not reliable/available on Windows.

Allocate an empty cache object, check cache objects for being empty
before using them.
Otherwise the code will re-read cache every 5 seconds, as NULL cache
does not trigger the code that stores mtime, which makes the cache
file appear modified/unloaded permanently.

https://bugzilla.gnome.org/show_bug.cgi?id=735696

1 files changed, 74 insertions, 17 deletions

diff --git a/src/xdgmimecache.c b/src/xdgmimecache.c
index 213027d..a50c8dc 100644
--- a/src/xdgmimecache.c
+++ b/src/xdgmimecache.c
@@ -161,6 +161,12 @@ _xdg_mime_cache_new_from_file (const char *file_name)
   if (fd != -1)
     close (fd);
 
+#else /* HAVE_MMAP */
+  cache = (XdgMimeCache *) malloc (sizeof (XdgMimeCache));
+  cache->minor = 0;
+  cache->ref_count = 1;
+  cache->buffer = NULL;
+  cache->size = 0;
 #endif  /* HAVE_MMAP */
 
   return cache;
@@ -306,10 +312,16 @@ cache_alias_lookup (const char *alias)
   for (i = 0; _caches[i]; i++)
     {
       XdgMimeCache *cache = _caches[i];
-      xdg_uint32_t list_offset = GET_UINT32 (cache->buffer, 4);
-      xdg_uint32_t n_entries = GET_UINT32 (cache->buffer, list_offset);
+      xdg_uint32_t list_offset;
+      xdg_uint32_t n_entries;
       xdg_uint32_t offset;
 
+      if (cache->buffer == NULL)
+        continue;
+
+      list_offset = GET_UINT32 (cache->buffer, 4);
+      n_entries = GET_UINT32 (cache->buffer, list_offset);
+
       min = 0; 
       max = n_entries - 1;
       while (max >= min) 
@@ -352,10 +364,16 @@ cache_glob_lookup_literal (const char *file_name,
   for (i = 0; _caches[i]; i++)
     {
       XdgMimeCache *cache = _caches[i];
-      xdg_uint32_t list_offset = GET_UINT32 (cache->buffer, 12);
-      xdg_uint32_t n_entries = GET_UINT32 (cache->buffer, list_offset);
+      xdg_uint32_t list_offset;
+      xdg_uint32_t n_entries;
       xdg_uint32_t offset;
 
+      if (cache->buffer == NULL)
+        continue;
+
+      list_offset = GET_UINT32 (cache->buffer, 12);
+      n_entries = GET_UINT32 (cache->buffer, list_offset);
+
       min = 0; 
       max = n_entries - 1;
       while (max >= min) 
@@ -408,8 +426,14 @@ cache_glob_lookup_fnmatch (const char *file_name,
     {
       XdgMimeCache *cache = _caches[i];
 
-      xdg_uint32_t list_offset = GET_UINT32 (cache->buffer, 20);
-      xdg_uint32_t n_entries = GET_UINT32 (cache->buffer, list_offset);
+      xdg_uint32_t list_offset;
+      xdg_uint32_t n_entries;
+
+      if (cache->buffer == NULL)
+        continue;
+
+      list_offset = GET_UINT32 (cache->buffer, 20);
+      n_entries = GET_UINT32 (cache->buffer, list_offset);
 
       for (j = 0; j < n_entries && n < n_mime_types; j++)
 	{
@@ -532,9 +556,16 @@ cache_glob_lookup_suffix (const char *file_name,
     {
       XdgMimeCache *cache = _caches[i];
 
-      xdg_uint32_t list_offset = GET_UINT32 (cache->buffer, 16);
-      xdg_uint32_t n_entries = GET_UINT32 (cache->buffer, list_offset);
-      xdg_uint32_t offset = GET_UINT32 (cache->buffer, list_offset + 4);
+      xdg_uint32_t list_offset;
+      xdg_uint32_t n_entries;
+      xdg_uint32_t offset;
+
+      if (cache->buffer == NULL)
+        continue;
+
+      list_offset = GET_UINT32 (cache->buffer, 16);
+      n_entries = GET_UINT32 (cache->buffer, list_offset);
+      offset = GET_UINT32 (cache->buffer, list_offset + 4);
 
       n = cache_glob_node_lookup_suffix (cache, 
 					 n_entries, offset, 
@@ -641,6 +672,9 @@ _xdg_mime_cache_get_max_buffer_extents (void)
     {
       XdgMimeCache *cache = _caches[i];
 
+      if (cache->buffer == NULL)
+        continue;
+
       offset = GET_UINT32 (cache->buffer, 24);
       max_extent = MAX (max_extent, GET_UINT32 (cache->buffer, offset + 4));
     }
@@ -667,6 +701,9 @@ cache_get_mime_type_for_data (const void *data,
       int prio;
       const char *match;
 
+      if (cache->buffer == NULL)
+        continue;
+
       match = cache_magic_lookup_data (cache, data, len, &prio);
       if (prio > priority)
 	{
@@ -868,11 +905,16 @@ _xdg_mime_cache_mime_type_subclass (const char *mime,
   for (i = 0; _caches[i]; i++)
     {
       XdgMimeCache *cache = _caches[i];
-      
-      xdg_uint32_t list_offset = GET_UINT32 (cache->buffer, 8);
-      xdg_uint32_t n_entries = GET_UINT32 (cache->buffer, list_offset);
+      xdg_uint32_t list_offset;
+      xdg_uint32_t n_entries;
       xdg_uint32_t offset, n_parents, parent_offset;
 
+      if (cache->buffer == NULL)
+        continue;
+
+      list_offset = GET_UINT32 (cache->buffer, 8);
+      n_entries = GET_UINT32 (cache->buffer, list_offset);
+
       min = 0; 
       max = n_entries - 1;
       while (max >= min)
@@ -934,9 +976,14 @@ _xdg_mime_cache_list_mime_parents (const char *mime)
   for (i = 0; _caches[i]; i++)
     {
       XdgMimeCache *cache = _caches[i];
-  
-      xdg_uint32_t list_offset = GET_UINT32 (cache->buffer, 8);
-      xdg_uint32_t n_entries = GET_UINT32 (cache->buffer, list_offset);
+      xdg_uint32_t list_offset;
+      xdg_uint32_t n_entries;
+
+      if (cache->buffer == NULL)
+        continue;
+
+      list_offset = GET_UINT32 (cache->buffer, 8);
+      n_entries = GET_UINT32 (cache->buffer, list_offset);
 
       for (j = 0; j < n_entries; j++)
 	{
@@ -986,10 +1033,16 @@ cache_lookup_icon (const char *mime, int header)
   for (i = 0; _caches[i]; i++)
     {
       XdgMimeCache *cache = _caches[i];
-      xdg_uint32_t list_offset = GET_UINT32 (cache->buffer, header);
-      xdg_uint32_t n_entries = GET_UINT32 (cache->buffer, list_offset);
+      xdg_uint32_t list_offset;
+      xdg_uint32_t n_entries;
       xdg_uint32_t offset;
 
+      if (cache->buffer == NULL)
+        continue;
+
+      list_offset = GET_UINT32 (cache->buffer, header);
+      n_entries = GET_UINT32 (cache->buffer, list_offset);
+
       min = 0; 
       max = n_entries - 1;
       while (max >= min) 
@@ -1066,6 +1119,10 @@ _xdg_mime_cache_glob_dump (void)
     xdg_uint32_t list_offset;
     xdg_uint32_t n_entries;
     xdg_uint32_t offset;
+
+    if (cache->buffer == NULL)
+      continue;
+
     list_offset = GET_UINT32 (cache->buffer, 16);
     n_entries = GET_UINT32 (cache->buffer, list_offset);
     offset = GET_UINT32 (cache->buffer, list_offset + 4);