[fsp] Buffer consecutive Write() calls.

chrome/browser/chromeos/file_system_provider/fileapi/buffering_file_stream_writer.h

+// Copyright 2014 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 CHROME_BROWSER_CHROMEOS_FILE_SYSTEM_PROVIDER_FILEAPI_BUFFERING_FILE_STREAM_WRITER_H_
+#define CHROME_BROWSER_CHROMEOS_FILE_SYSTEM_PROVIDER_FILEAPI_BUFFERING_FILE_STREAM_WRITER_H_
+
+#include "base/basictypes.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/weak_ptr.h"
+#include "storage/browser/fileapi/file_stream_writer.h"
+
+namespace net {
+class IOBuffer;
+}  // namespace net
+
+namespace chromeos {
+namespace file_system_provider {
+
+// Wraps the file stream writer implementation with an intermediate buffer.
+// Writes data from the inner file stream writer in chunks of size at least
+// |intermediate_buffer_length| bytes (or less for the last chunk, or when
+// Flush() is explicitely called).
+//
+// The underlying inner file stream writer *must not* return any values
+// synchronously. Instead, results must be returned by a callback, including
+// errors. Moreover, partial writes are *not* supported.
+class BufferingFileStreamWriter : public storage::FileStreamWriter {
+ public:
+  BufferingFileStreamWriter(
+      scoped_ptr<storage::FileStreamWriter> file_stream_writer,
+      int intermediate_buffer_length);
+
+  virtual ~BufferingFileStreamWriter();
+
+  // storage::FileStreamWriter overrides.
+  virtual int Write(net::IOBuffer* buf,
+                    int buf_len,
+                    const net::CompletionCallback& callback) override;
+  virtual int Cancel(const net::CompletionCallback& callback) override;
+  virtual int Flush(const net::CompletionCallback& callback) override;
+
+ private:
+  // Copies |buffer_length| bytes of data from the |buffer| starting at
+  // |buffer_offset| position to the current position of the intermediate
+  // buffer.
+  void CopyToIntermediateBuffer(scoped_refptr<net::IOBuffer> buffer,
+                                int buffer_offset,
+                                int buffer_length);
+
+  // Flushes all of the bytes in the intermediate buffer to the inner file
+  // stream writer.
+  void FlushIntermediateBuffer(const net::CompletionCallback& callback);
+
+  // Called when flushing the intermediate buffer is completed with either
+  // a success or an error.
+  void OnFlushIntermediateBufferCompleted(
+      int length,
+      const net::CompletionCallback& callback,
+      int result);
+
+  // Called when flushing the intermediate buffer for direct write is completed
+  // with either a success or an error.
+  void OnFlushIntermediateBufferForDirectWriteCompleted(
+      scoped_refptr<net::IOBuffer> buffer,
+      int length,
+      const net::CompletionCallback& callback,
+      int result);
+
+  // Called when flushing the intermediate buffer for a buffered write is
+  // completed with either a success or an error.
+  void OnFlushIntermediateBufferForBufferedWriteCompleted(
+      scoped_refptr<net::IOBuffer> buffer,
+      int buffered_bytes,
+      int bytes_left,
+      const net::CompletionCallback& callback,
+      int result);
+
+  // Called when flushing the intermediate buffer for a flush call is completed
+  // with either a success or an error.
+  void OnFlushIntermediateBufferForFlushCompleted(
+      const net::CompletionCallback& callback,
+      int result);
+
+  scoped_ptr<storage::FileStreamWriter> file_stream_writer_;
+  int intermediate_buffer_length_;
+  scoped_refptr<net::IOBuffer> intermediate_buffer_;
+  int buffered_bytes_;
+
+  base::WeakPtrFactory<BufferingFileStreamWriter> weak_ptr_factory_;
+  DISALLOW_COPY_AND_ASSIGN(BufferingFileStreamWriter);
+};
+
+}  // namespace file_system_provider
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_CHROMEOS_FILE_SYSTEM_PROVIDER_FILEAPI_BUFFERING_FILE_STREAM_WRITER_H_