Http cache: Add support for a dedicated cache thread.

net/http/http_cache.h

 // Copyright (c) 2010 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.
 
 // This file declares a HttpTransactionFactory implementation that can be
 // layered on top of another HttpTransactionFactory to add HTTP caching.  The
 // caching logic follows RFC 2616 (any exceptions are called out in the code).
 //
 // The HttpCache takes a disk_cache::Backend as a parameter, and uses that for
 // the cache storage.
@@ skipping 10 matching lines @@
 #include "base/file_path.h"
 #include "base/hash_tables.h"
 #include "base/scoped_ptr.h"
 #include "base/task.h"
 #include "base/weak_ptr.h"
 #include "net/base/cache_type.h"
 #include "net/base/completion_callback.h"
 #include "net/http/http_transaction_factory.h"
 
 class GURL;
+class MessageLoop;
 class ViewCacheHelper;
 
 namespace disk_cache {
 class Backend;
 class Entry;
 }
 
 namespace net {
 
 class HostResolver;
@@ skipping 21 matching lines @@
     // standard invalidations.
     PLAYBACK,
     // Disables reads and writes from the cache.
     // Equivalent to setting LOAD_DISABLE_CACHE on every request.
     DISABLE
   };
 
   // Initialize the cache from the directory where its data is stored. The
   // disk cache is initialized lazily (by CreateTransaction) in this case. If
   // |cache_size| is zero, a default value will be calculated automatically.
+  // The |cache_thread| is the thread where disk operations should take place.
   HttpCache(NetworkChangeNotifier* network_change_notifier,
             HostResolver* host_resolver,
             ProxyService* proxy_service,
             SSLConfigService* ssl_config_service,
             HttpAuthHandlerFactory* http_auth_handler_factory,
             const FilePath& cache_dir,
+            MessageLoop* cache_thread,
             int cache_size);
 
   // Initialize the cache from the directory where its data is stored. The
   // disk cache is initialized lazily (by CreateTransaction) in  this case. If
   // |cache_size| is zero, a default value will be calculated automatically.
   // Provide an existing HttpNetworkSession, the cache can construct a
   // network layer with a shared HttpNetworkSession in order for multiple
   // network layers to share information (e.g. authenication data).
+  // The |cache_thread| is the thread where disk operations should take place.
   HttpCache(HttpNetworkSession* session, const FilePath& cache_dir,
-            int cache_size);
+            MessageLoop* cache_thread, int cache_size);
 
   // Initialize using an in-memory cache. The cache is initialized lazily
   // (by CreateTransaction) in this case. If |cache_size| is zero, a default
   // value will be calculated automatically.
   HttpCache(NetworkChangeNotifier* network_change_notifier,
             HostResolver* host_resolver,
             ProxyService* proxy_service,
             SSLConfigService* ssl_config_service,
             HttpAuthHandlerFactory* http_auth_handler_factory,
             int cache_size);
 
   // Initialize the cache from its component parts, which is useful for
   // testing.  The lifetime of the network_layer and disk_cache are managed by
   // the HttpCache and will be destroyed using |delete| when the HttpCache is
   // destroyed.
   HttpCache(HttpTransactionFactory* network_layer,
             disk_cache::Backend* disk_cache);
 
   HttpTransactionFactory* network_layer() { return network_layer_.get(); }
 
   // Returns the cache backend for this HttpCache instance. If the backend
   // is not initialized yet, this method will initialize it. If the return
   // value is NULL then the backend cannot be initialized.
+  // This method is deprecated.
   disk_cache::Backend* GetBackend();
 
+  // Retrieves the cache backend for this HttpCache instance. If the backend
+  // is not initialized yet, this method will initialize it. The return value is
+  // a network error code, and it could be ERR_IO_PENDING, in which case the
+  // |callback| will be notified when the operation completes. The pointer that
+  // receives the |backend| must remain valid until the operation completes.
+  int GetBackend(disk_cache::Backend** backend, CompletionCallback* callback);
+
   // HttpTransactionFactory implementation:
   virtual int CreateTransaction(scoped_ptr<HttpTransaction>* trans);
   virtual HttpCache* GetCache();
   virtual HttpNetworkSession* GetSession();
   virtual void Suspend(bool suspend);
 
   // Helper function for reading response info from the disk cache.  If the
   // cache doesn't have the whole resource *|request_truncated| is set to true.
   // Avoid this function for performance critical paths as it uses blocking IO.
   static bool ReadResponseInfo(disk_cache::Entry* disk_entry,
@@ skipping 71 matching lines @@
     bool               doomed;
 
     explicit ActiveEntry(disk_cache::Entry*);
     ~ActiveEntry();
   };
 
   typedef base::hash_map<std::string, ActiveEntry*> ActiveEntriesMap;
   typedef base::hash_map<std::string, NewEntry*> NewEntriesMap;
   typedef std::set<ActiveEntry*> ActiveEntriesSet;
 
-
   // Methods ------------------------------------------------------------------
 
   // Generates the cache key for this request.
   std::string GenerateCacheKey(const HttpRequestInfo*);
 
   // Dooms the entry selected by |key|. |trans| will be notified via its IO
   // callback if this method returns ERR_IO_PENDING. The entry can be
   // currently in use or not.
   int DoomEntry(const std::string& key, Transaction* trans);
 
@@ skipping 87 matching lines @@
   // Callbacks ----------------------------------------------------------------
 
   // Processes BackendCallback notifications.
   void OnIOComplete(int result, NewEntry* entry);
 
 
   // Variables ----------------------------------------------------------------
 
   // Used when lazily constructing the disk_cache_.
   FilePath disk_cache_dir_;
+  MessageLoop* cache_thread_;
 
   Mode mode_;
   CacheType type_;
 
   scoped_ptr<HttpTransactionFactory> network_layer_;
   scoped_ptr<disk_cache::Backend> disk_cache_;
 
   // The set of active entries indexed by cache key.
   ActiveEntriesMap active_entries_;
 
@@ skipping 10 matching lines @@
 
   typedef base::hash_map<std::string, int> PlaybackCacheMap;
   scoped_ptr<PlaybackCacheMap> playback_cache_map_;
 
   DISALLOW_COPY_AND_ASSIGN(HttpCache);
 };
 
 }  // namespace net
 
 #endif  // NET_HTTP_HTTP_CACHE_H_