Disk cache: Add explicit support for eviction / deletion

of sparse entries.

I started to add code to modify the children_map of the
parent entry when a child is evicted but that ended up
being too much trouble for too little gain. We have to be
prepared to handle the case of not finding a child entry
because there is no way to make sure that the process
doesn't go away at any time, so adding a lot of complexity
just to avoid an extra entry lookup is just not worth it.

On the other hand, potentially freeing up a lot of space when
a sparse entry is deleted (insetad of just waiting for the
eviction code to do the cleanup) seems like a good thing.

BUG=12258
TEST=unittest

Review URL: http://codereview.chromium.org/149306

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@20325 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 8 insertions, 1 deletions

diff --git a/net/disk_cache/disk_format.h b/net/disk_cache/disk_format.h
index d1f7fed..c98fc34 100644
--- a/net/disk_cache/disk_format.h
+++ b/net/disk_cache/disk_format.h
@@ -123,7 +123,8 @@ struct EntryStore {
   CacheAddr   long_key;           // Optional address of a long key.
   int32       data_size[4];       // We can store up to 4 data streams for each
   CacheAddr   data_addr[4];       // entry.
-  int32       pad[6];
+  uint32      flags;              // Any combination of EntryFlags.
+  int32       pad[5];
   char        key[256 - 24 * 4];  // null terminated
 };
 
@@ -138,6 +139,12 @@ enum EntryState {
   ENTRY_DOOMED      // The entry was doomed.
 };
 
+// Flags that can be applied to an entry.
+enum EntryFlags {
+  PARENT_ENTRY = 1,         // This entry has children (sparse) entries.
+  CHILD_ENTRY = 1 << 1      // Child entry that stores sparse data.
+};
+
 #pragma pack(push, 4)
 // Rankings information for a given entry.
 struct RankingsNode {