AU: Speed up updates by using buffered writes.
Given that SSD writes are really slow, this improves performance significantly.
This reduces update time on AGZ from 375 to 100 seconds.
BUG=6901
TEST=unit tests, gmerged on device and measured speed
Change-Id: Idac7743f6eaa8f26878a2d1f6b9401513e2ca600
Review URL: http://codereview.chromium.org/3471006
diff --git a/buffered_file_writer.h b/buffered_file_writer.h
new file mode 100644
index 0000000..0457285
--- /dev/null
+++ b/buffered_file_writer.h
@@ -0,0 +1,53 @@
+// Copyright (c) 2010 The Chromium OS 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 CHROMEOS_PLATFORM_UPDATE_ENGINE_BUFFERED_FILE_WRITER_H__
+#define CHROMEOS_PLATFORM_UPDATE_ENGINE_BUFFERED_FILE_WRITER_H__
+
+#include <base/scoped_ptr.h>
+#include <gtest/gtest_prod.h> // for FRIEND_TEST
+
+#include "update_engine/file_writer.h"
+
+// BufferedFileWriter is an implementation of FileWriter that buffers all data
+// before passing it onto another FileWriter.
+
+namespace chromeos_update_engine {
+
+class BufferedFileWriter : public FileWriter {
+ public:
+ BufferedFileWriter(FileWriter* next, size_t buffer_size);
+ virtual ~BufferedFileWriter();
+
+ virtual int Open(const char* path, int flags, mode_t mode);
+ virtual ssize_t Write(const void* bytes, size_t count);
+ virtual int Close();
+
+ private:
+ FRIEND_TEST(BufferedFileWriterTest, CloseErrorTest);
+ FRIEND_TEST(BufferedFileWriterTest, CloseNoDataTest);
+ FRIEND_TEST(BufferedFileWriterTest, CloseWriteErrorTest);
+ FRIEND_TEST(BufferedFileWriterTest, ConstructorTest);
+ FRIEND_TEST(BufferedFileWriterTest, WriteBufferNoDataTest);
+ FRIEND_TEST(BufferedFileWriterTest, WriteBufferTest);
+ FRIEND_TEST(BufferedFileWriterTest, WriteErrorTest);
+ FRIEND_TEST(BufferedFileWriterTest, WriteTest);
+ FRIEND_TEST(BufferedFileWriterTest, WriteWrapBufferTest);
+
+ // If non-empty, sends the buffer to the next FileWriter.
+ ssize_t WriteBuffer();
+
+ // The FileWriter that we write all buffered data to.
+ FileWriter* const next_;
+
+ scoped_array<char> buffer_;
+ size_t buffer_size_;
+ size_t buffered_bytes_;
+
+ DISALLOW_COPY_AND_ASSIGN(BufferedFileWriter);
+};
+
+} // namespace chromeos_update_engine
+
+#endif // CHROMEOS_PLATFORM_UPDATE_ENGINE_BUFFERED_FILE_WRITER_H__