Http cache: Add support for a dedicated cache thread.

net/disk_cache/disk_cache.h

-// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
+// Copyright (c) 2006-2010 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.
 
 // Defines the public interface of the disk cache. For more details see
 // http://dev.chromium.org/developers/design-documents/disk-cache
 
 #ifndef NET_DISK_CACHE_DISK_CACHE_H_
 #define NET_DISK_CACHE_DISK_CACHE_H_
 
 #include <string>
 #include <vector>
 
 #include "base/basictypes.h"
 #include "base/time.h"
 #include "net/base/cache_type.h"
 #include "net/base/completion_callback.h"
 
 class FilePath;
+class MessageLoop;
 
 namespace net {
 class IOBuffer;
 }
 
 namespace disk_cache {
 
 class Entry;
 class Backend;
 typedef net::CompletionCallback CompletionCallback;
@@ skipping 19 matching lines @@
 // Note: This function is deprecated.
 Backend* CreateInMemoryCacheBackend(int max_bytes);
 
 // Returns an instance of a Backend of the given |type|. |path| points to a
 // folder where the cached data will be stored (if appropriate). This cache
 // instance must be the only object that will be reading or writing files to
 // that folder. The returned object should be deleted when not needed anymore.
 // If |force| is true, and there is a problem with the cache initialization, the
 // files will be deleted and a new set will be created. |max_bytes| is the
 // maximum size the cache can grow to. If zero is passed in as |max_bytes|, the
-// cache will determine the value to use. The returned pointer can be NULL if a
-// fatal error is found. The actual return value of the function is a net error
-// code. If this function returns ERR_IO_PENDING, the |callback| will be invoked
-// when a backend is available or a fatal error condition is reached. The
-// pointer to receive the |backend| must remain valid until the operation
-// completes.
+// cache will determine the value to use. |thread| can be used to perform IO
+// operations if a dedicated thread is required; a valid value is expected for
+// any backend that performs operations on a disk. The returned pointer can be
+// NULL if a fatal error is found. The actual return value of the function is a
+// net error code. If this function returns ERR_IO_PENDING, the |callback| will
+// be invoked when a backend is available or a fatal error condition is reached.
+// The pointer to receive the |backend| must remain valid until the operation
+// completes (the callback is notified).
 int CreateCacheBackend(net::CacheType type, const FilePath& path, int max_bytes,
-                       bool force, Backend** backend,
+                       bool force, MessageLoop* thread, Backend** backend,
                        CompletionCallback* callback);
 
 // The root interface for a disk cache instance.
 class Backend {
  public:
   // If the backend is destroyed when there are operations in progress (any
   // callback that has not been invoked yet), this method cancels said
   // operations so the callbacks are not invoked, possibly leaving the work
   // half way (for instance, dooming just a few entries). Note that pending IO
   // for a given Entry (as opposed to the Backend) will still generate a
@@ skipping 268 matching lines @@
   // Note: This method is deprecated.
   virtual int ReadyForSparseIO(CompletionCallback* completion_callback) = 0;
 
  protected:
   virtual ~Entry() {}
 };
 
 }  // namespace disk_cache
 
 #endif  // NET_DISK_CACHE_DISK_CACHE_H_