Asynchronous initialization in Simple Index.

net/disk_cache/simple/simple_disk_format.h

 // Copyright (c) 2013 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.
 
 #ifndef NET_DISK_CACHE_SIMPLE_SIMPLE_DISK_FORMAT_H_
 #define NET_DISK_CACHE_SIMPLE_SIMPLE_DISK_FORMAT_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 41 matching lines @@
 // -------------------------
 namespace SimpleIndexFile {
   // Simple Index File metadata is defined here.
   struct Header {
     uint64 initial_magic_number;
     uint32 version;
     uint64 number_of_entries;
     uint64 cache_size;  // Total cache storage size in bytes.
   };
 
+  // TODO(felipeg): At some point we should consider using a protobuffer.  See
+  // that we are re-implementing most of protobuffer's functionality such as
+  // Serialize and Merge.
   // We must keep this struct a POD.
   struct EntryMetadata {
     EntryMetadata();
     EntryMetadata(const std::string& hash_key_p,
                   base::Time last_used_time_p,
                   uint64 entry_size_p);
 
     base::Time GetLastUsedTime() const;
     std::string GetHashKey() const;
     void SetLastUsedTime(const base::Time& last_used_time_p);
 
+    // Serialize the data from |in_entry_metadata| and appends the bytes in
+    // |out_buffer|. The serialization is platform dependent since it simply
+    // writes the whole struct from memory into the given buffer.
     static void Serialize(const EntryMetadata& in_entry_metadata,
                           std::string* out_buffer);
 
     static void DeSerialize(const char* in_buffer,
                             EntryMetadata* out_entry_metadata);
 
+    // Merge two EntryMetadata instances.
+    // The existing valid data in |out_entry_metadata| will prevail.
+    static void Merge(const EntryMetadata& entry_metadata,
+                      EntryMetadata* out_entry_metadata);
+
     char hash_key[kEntryHashKeySize];  // Not a c_string, not null terminated.
 
     // This is the serialized format from Time::ToInternalValue().
     // If you want to make calculations/comparisons, you should use the
     // base::Time() class. Use the GetLastUsedTime() method above.
     int64 last_used_time;
 
     uint64 entry_size;  // Storage size in bytes.
   };
 
   const size_t kEntryMetadataSize = sizeof(EntryMetadata);
 
   struct Footer {
     uint32 crc;
   };
 
 }  // namespace SimpleIndexFile
 
 }  // namespace disk_cache
 
 #endif  // NET_DISK_CACHE_SIMPLE_SIMPLE_DISK_FORMAT_H_