Implement async verision of FileSystemFileUtil and in-memory file system for testing purposes.

webkit/chromeos/fileapi/async_file_stream.h

+// Copyright (c) 2011 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 WEBKIT_CHROMEOS_FILEAPI_ASYNC_FILE_STREAM_H_
+#define WEBKIT_CHROMEOS_FILEAPI_ASYNC_FILE_STREAM_H_
+
+#include "base/platform_file.h"
+#include "base/callback.h"
+
+namespace fileapi {
+
+using base::PlatformFileError;
+
+// Abstract class similar to net::FileStream, but supporting only
+// the asyncronous operations and not necessarily relying on PlatformFile.
+class AsyncFileStream {
+ public:
+  // Used for Read() and Write(). |result| is the return code of the
+  // operation, and |length| is the length of data read or written.
+  typedef base::Callback<void(PlatformFileError result,
+                              int64 length)> ReadWriteCallback;
+
+  // Used for Seek(). |result| is the return code of the operation.
+  typedef base::Callback<void(PlatformFileError)> SeekCallback;
+
+  virtual ~AsyncFileStream() {};
+
+  // Reads data from the current stream position. Up to |length| bytes
+  // will be read from |buffer|. The memory pointed to by |buffer| must
+  // remain valid until the callback is called.
+  virtual void Read(char* buffer,
+                    int64 length,
+                    const ReadWriteCallback& callback) = 0;
+
+  // Writes data at the current stream position. Up to |length| bytes will
+  // be written from |buffer|. The memory pointed to by |buffer| must
+  // remain valid until the callback is called.
+  virtual void Write(const char* buffer,
+                     int64 length,
+                     const ReadWriteCallback& callback) = 0;
+
+  virtual void Seek(int64 offset,
+                    const SeekCallback& callback) = 0;
+};
+
+}  // namespace fileapi
+
+#endif  // WEBKIT_CHROMEOS_FILEAPI_ASYNC_FILE_STREAM_H_