Reduce copy on QuotaFileIO::Write

webkit/plugins/ppapi/quota_file_io.cc

 // Copyright (c) 2012 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.
 
 #include "webkit/plugins/ppapi/quota_file_io.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/memory/weak_ptr.h"
 #include "base/message_loop_proxy.h"
 #include "base/stl_util.h"
+#include "base/task_runner_util.h"
 #include "webkit/plugins/ppapi/host_globals.h"
 #include "webkit/plugins/ppapi/ppapi_plugin_instance.h"
 #include "webkit/plugins/ppapi/resource_helper.h"
 
 using base::PlatformFile;
 using base::PlatformFileError;
 using quota::StorageType;
 
 namespace webkit {
 namespace ppapi {
@@ skipping 69 matching lines @@
       return;
     }
     DCHECK(buffer_.get());
 
     PluginDelegate* plugin_delegate = quota_io_->GetPluginDelegate();
     if (!plugin_delegate) {
       DidFail(base::PLATFORM_FILE_ERROR_FAILED);
       return;
     }
 
-    if (!base::FileUtilProxy::Write(
-            plugin_delegate->GetFileThreadMessageLoopProxy(),
-            quota_io_->file_, offset_, buffer_.get(), bytes_to_write_,
-            base::Bind(&WriteOperation::DidFinish,
+    if (!base::PostTaskAndReplyWithResult(
+            plugin_delegate->GetFileThreadMessageLoopProxy(), FROM_HERE,
+            base::Bind(&base::WritePlatformFile,
+                       quota_io_->file_, offset_,
+                       base::Owned(buffer_.release()),
+                       bytes_to_write_),
+            base::Bind(&WriteOperation::DidWrite,
                        weak_factory_.GetWeakPtr()))) {
       DidFail(base::PLATFORM_FILE_ERROR_FAILED);
       return;
     }
   }
 
   virtual void DidFail(PlatformFileError error) OVERRIDE {
     DidFinish(error, 0);
   }
 
   bool finished() const { return finished_; }
 
   virtual void WillRunCallback() {
     base::MessageLoopProxy::current()->PostTask(
         FROM_HERE,
         base::Bind(&WriteOperation::RunCallback, weak_factory_.GetWeakPtr()));
   }
 
  private:
+  void DidWrite(int bytes_written) {
+    base::PlatformFileError error = bytes_written >= 0 ?

[brettw, 2013/01/09 20:17:10]

What happens if you write 0 bytes? It looks like before this may have succeeded,
and now it will report failure.

[tzik, 2013/01/10 04:02:36]

Right, this changes its behavior for 0-byte write.
Fixed.

+        base::PLATFORM_FILE_OK : base::PLATFORM_FILE_ERROR_FAILED;
+    DidFinish(error, bytes_written);
+  }
+
   void DidFinish(PlatformFileError status, int bytes_written) {
     finished_ = true;
     status_ = status;
     bytes_written_ = bytes_written;
     int64_t max_offset =
         (status != base::PLATFORM_FILE_OK) ? 0 : offset_ + bytes_written;
     // This may delete itself by calling RunCallback.
     quota_io_->DidWrite(this, max_offset);
   }
 
@@ skipping 259 matching lines @@
 
 
   PluginDelegate* plugin_delegate = GetPluginDelegate();
   if (plugin_delegate)
     plugin_delegate->DidUpdateFile(file_url_, delta);
   inflight_operations_ = 0;
 }
 
 }  // namespace ppapi
 }  // namespace webkit