Disk cache: Add support for an extra data stream for each cache entry.

This is the first step to allow the http cache to store additional metadata
for certain entries.

The cache file format changes to version 2.0 so an effect of this cl is
that the borwser will discard the old cache files.

Review URL: http://codereview.chromium.org/12880

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@6392 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 28 insertions, 6 deletions

diff --git a/net/disk_cache/disk_format.h b/net/disk_cache/disk_format.h
index d874359..2e839a1 100644
--- a/net/disk_cache/disk_format.h
+++ b/net/disk_cache/disk_format.h
@@ -36,7 +36,7 @@
 // entry keeps track of all the information related to the same cache entry,
 // such as the key, hash value, data pointers etc. A rankings node keeps track
 // of the information that is updated frequently for a given entry, such as its
-// location on the LRU list, last access time etc.
+// location on the LRU lists, last access time etc.
 //
 // The files that store internal information for the cache (blocks and index)
 // are at least partially memory mapped. They have a location that is signaled
@@ -63,7 +63,16 @@ typedef uint32 CacheAddr;
 
 const int kIndexTablesize = 0x10000;
 const uint32 kIndexMagic = 0xC103CAC3;
-const uint32 kCurrentVersion = 0x10003;  // Version 1.3.
+const uint32 kCurrentVersion = 0x20000;  // Version 2.0.
+
+struct LruData {
+  CacheAddr heads[5];
+  CacheAddr tails[5];
+  CacheAddr transaction;     // In-flight operation target.
+  int32     operation;       // Actual in-flight operation.
+  int32     operation_list;  // In-flight operation list.
+  int32     pad[7];
+};
 
 // Header for the master index file.
 struct IndexHeader {
@@ -75,7 +84,8 @@ struct IndexHeader {
   int32       this_id;       // Id for all entries being changed (dirty flag).
   CacheAddr   stats;         // Storage for usage data.
   int32       table_len;     // Actual size of the table (0 == kIndexTablesize).
-  int32       pad[8];
+  int32       pad[64];
+  LruData     lru;           // Eviction control data.
   IndexHeader() {
     memset(this, 0, sizeof(*this));
     magic = kIndexMagic;
@@ -99,17 +109,29 @@ struct EntryStore {
   uint32      hash;               // Full hash of the key.
   CacheAddr   next;               // Next entry with the same hash or bucket.
   CacheAddr   rankings_node;      // Rankings node for this entry.
+  int32       reuse_count;        // How often is this entry used.
+  int32       refetch_count;      // How often is this fetched from the net.
+  int32       state;              // Current state.
+  uint64      creation_time;
   int32       key_len;
   CacheAddr   long_key;           // Optional address of a long key.
-  int32       data_size[2];       // We can store up to 2 data chunks for each
-  CacheAddr   data_addr[2];       // entry.
-  char        key[256 - 9 * 4];   // null terminated
+  int32       data_size[4];       // We can store up to 4 data streams for each
+  CacheAddr   data_addr[4];       // entry.
+  int32       pad[6];
+  char        key[256 - 24 * 4];  // null terminated
 };
 
 COMPILE_ASSERT(sizeof(EntryStore) == 256, bad_EntyStore);
 const int kMaxInternalKeyLength = 4 * sizeof(EntryStore) -
                                   offsetof(EntryStore, key) - 1;
 
+// Possible states for a given entry.
+enum EntryState {
+  ENTRY_NORMAL = 0,
+  ENTRY_EVICTED,    // The entry was recently evicted from the cache.
+  ENTRY_DOOMED      // The entry was doomed.
+};
+
 #pragma pack(push, old, 4)
 // Rankings information for a given entry.
 struct RankingsNode {