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// 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_READER_H_
#define CHROME_BROWSER_CHROMEOS_FILE_SYSTEM_PROVIDER_FILEAPI_BUFFERING_FILE_STREAM_READER_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/blob/file_stream_reader.h"
namespace net {
class IOBuffer;
} // namespace net
namespace chromeos {
namespace file_system_provider {
// Wraps the file stream reader implementation with a prefetching buffer.
// Reads data from the internal file stream reader in chunks of size at least
// |preloading_buffer_length| bytes (or less for the last chunk, because of
// EOF). Up to |max_bytes_to_read| of bytes can be requested in total.
//
// The underlying internal file stream reader *must not* return any values
// synchronously. Instead, results must be returned by a callback, including
// errors.
class BufferingFileStreamReader : public storage::FileStreamReader {
public:
BufferingFileStreamReader(
scoped_ptr<storage::FileStreamReader> file_stream_reader,
int preloading_buffer_length,
int64 max_bytes_to_read);
virtual ~BufferingFileStreamReader();
// storage::FileStreamReader overrides.
virtual int Read(net::IOBuffer* buf,
int buf_len,
const net::CompletionCallback& callback) override;
virtual int64 GetLength(
const net::Int64CompletionCallback& callback) override;
private:
// Copies data from the preloading buffer and updates the internal iterator.
// Returns number of bytes successfully copied.
int CopyFromPreloadingBuffer(scoped_refptr<net::IOBuffer> buffer,
int buffer_length);
// Preloads data from the internal stream reader and calls the |callback|.
void Preload(const net::CompletionCallback& callback);
void OnReadCompleted(const net::CompletionCallback& callback, int result);
// Called when preloading of a buffer chunk is finished. Updates state of the
// preloading buffer and copied requested data to the |buffer|.
void OnPreloadCompleted(scoped_refptr<net::IOBuffer> buffer,
int buffer_length,
const net::CompletionCallback& callback,
int result);
scoped_ptr<storage::FileStreamReader> file_stream_reader_;
int preloading_buffer_length_;
int64 max_bytes_to_read_;
int64 bytes_read_;
scoped_refptr<net::IOBuffer> preloading_buffer_;
int preloading_buffer_offset_;
int preloaded_bytes_;
base::WeakPtrFactory<BufferingFileStreamReader> weak_ptr_factory_;
DISALLOW_COPY_AND_ASSIGN(BufferingFileStreamReader);
};
} // namespace file_system_provider
} // namespace chromeos
#endif // CHROME_BROWSER_CHROMEOS_FILE_SYSTEM_PROVIDER_FILEAPI_BUFFERING_FILE_STREAM_READER_H_
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