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// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef CHROME_BROWSER_MEDIA_GALLERIES_FILEAPI_READAHEAD_FILE_STREAM_READER_H_
#define CHROME_BROWSER_MEDIA_GALLERIES_FILEAPI_READAHEAD_FILE_STREAM_READER_H_
#include <stdint.h>
#include "base/containers/queue.h"
#include "base/memory/weak_ptr.h"
#include "net/base/completion_once_callback.h"
#include "net/base/io_buffer.h"
#include "storage/browser/file_system/file_stream_reader.h"
// Wraps a source FileStreamReader with a readahead buffer.
class ReadaheadFileStreamReader : public storage::FileStreamReader {
public:
// Takes ownership of |source|.
explicit ReadaheadFileStreamReader(storage::FileStreamReader* source);
ReadaheadFileStreamReader(const ReadaheadFileStreamReader&) = delete;
ReadaheadFileStreamReader& operator=(const ReadaheadFileStreamReader&) =
delete;
~ReadaheadFileStreamReader() override;
// FileStreamReader overrides.
int Read(net::IOBuffer* buf,
int buf_len,
net::CompletionOnceCallback callback) override;
int64_t GetLength(net::Int64CompletionOnceCallback callback) override;
private:
// Returns the number of bytes consumed from the internal cache into |sink|.
// Returns an error code if we are out of cache, hit an error, or hit EOF.
int FinishReadFromCacheOrStoredError(net::DrainableIOBuffer* sink);
// Reads into a new buffer from the source reader. This calls
// OnFinishReadFromSource when it completes (either synchronously or
// asynchronously).
void ReadFromSourceIfNeeded();
void OnFinishReadFromSource(net::IOBuffer* buffer, int result);
// This is reset to NULL upon encountering a read error or EOF.
std::unique_ptr<storage::FileStreamReader> source_;
// This stores the error or EOF from the source FileStreamReader. Its
// value is undefined if |source_| is non-NULL.
int source_error_;
bool source_has_pending_read_;
// This contains a queue of buffers filled from |source_|, waiting to be
// consumed.
base::queue<scoped_refptr<net::DrainableIOBuffer>> buffers_;
// The read buffer waiting for the source FileStreamReader to finish
// reading and fill the cache.
scoped_refptr<net::DrainableIOBuffer> pending_sink_buffer_;
net::CompletionOnceCallback pending_read_callback_;
base::WeakPtrFactory<ReadaheadFileStreamReader> weak_factory_{this};
};
#endif // CHROME_BROWSER_MEDIA_GALLERIES_FILEAPI_READAHEAD_FILE_STREAM_READER_H_
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