Disk cache: Add explicit support for eviction / deletion...

net/disk_cache/disk_format.h

 // Copyright (c) 2006-2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // The cache is stored on disk as a collection of block-files, plus an index
 // file plus a collection of external files.
 //
 // Any data blob bigger than kMaxBlockSize (net/addr.h) will be stored on a
 // separate file named f_xxx where x is a hexadecimal number. Shorter data will
 // be stored as a series of blocks on a block-file. In any case, CacheAddr
@@ skipping 105 matching lines @@
   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[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
 };
 
 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.
 };
 
+// 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 {
   uint64      last_used;        // LRU info.
   uint64      last_modified;    // LRU info.
   CacheAddr   next;             // LRU list.
   CacheAddr   prev;             // LRU list.
   CacheAddr   contents;         // Address of the EntryStore.
   int32       dirty;            // The entry is being modifyied.
   void*       pointer;          // Pointer to the in-memory entry.
@@ skipping 94 matching lines @@
 };
 
 // The number of blocks stored by a child entry.
 const int kNumSparseBits = 1024;
 COMPILE_ASSERT(sizeof(SparseData) == sizeof(SparseHeader) + kNumSparseBits / 8,
                Invalid_SparseData_bitmap);
 
 }  // namespace disk_cache
 
 #endif  // NET_DISK_CACHE_DISK_FORMAT_H_