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      1 // Copyright 2014 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef CHROME_BROWSER_MEDIA_GALLERIES_FILEAPI_READAHEAD_FILE_STREAM_READER_H_
      6 #define CHROME_BROWSER_MEDIA_GALLERIES_FILEAPI_READAHEAD_FILE_STREAM_READER_H_
      7 
      8 #include <queue>
      9 
     10 #include "base/memory/weak_ptr.h"
     11 #include "net/base/io_buffer.h"
     12 #include "storage/browser/blob/file_stream_reader.h"
     13 
     14 // Wraps a source FileStreamReader with a readahead buffer.
     15 class ReadaheadFileStreamReader
     16     : public NON_EXPORTED_BASE(storage::FileStreamReader) {
     17  public:
     18   // Takes ownership of |source|.
     19   explicit ReadaheadFileStreamReader(storage::FileStreamReader* source);
     20 
     21   virtual ~ReadaheadFileStreamReader();
     22 
     23   // FileStreamReader overrides.
     24   virtual int Read(net::IOBuffer* buf, int buf_len,
     25                    const net::CompletionCallback& callback) OVERRIDE;
     26   virtual int64 GetLength(
     27       const net::Int64CompletionCallback& callback) OVERRIDE;
     28 
     29  private:
     30   // Returns the number of bytes consumed from the internal cache into |sink|.
     31   // Returns an error code if we are out of cache, hit an error, or hit EOF.
     32   int FinishReadFromCacheOrStoredError(net::DrainableIOBuffer* sink);
     33 
     34   // Reads into a new buffer from the source reader. This calls
     35   // OnFinishReadFromSource when it completes (either synchronously or
     36   // asynchronously).
     37   void ReadFromSourceIfNeeded();
     38   void OnFinishReadFromSource(net::IOBuffer* buffer, int result);
     39 
     40   // This is reset to NULL upon encountering a read error or EOF.
     41   scoped_ptr<storage::FileStreamReader> source_;
     42 
     43   // This stores the error or EOF from the source FileStreamReader. Its
     44   // value is undefined if |source_| is non-NULL.
     45   int source_error_;
     46   bool source_has_pending_read_;
     47 
     48   // This contains a queue of buffers filled from |source_|, waiting to be
     49   // consumed.
     50   std::queue<scoped_refptr<net::DrainableIOBuffer> > buffers_;
     51 
     52   // The read buffer waiting for the source FileStreamReader to finish
     53   // reading and fill the cache.
     54   scoped_refptr<net::DrainableIOBuffer> pending_sink_buffer_;
     55   net::CompletionCallback pending_read_callback_;
     56 
     57   base::WeakPtrFactory<ReadaheadFileStreamReader> weak_factory_;
     58 
     59   DISALLOW_COPY_AND_ASSIGN(ReadaheadFileStreamReader);
     60 };
     61 
     62 #endif  // CHROME_BROWSER_MEDIA_GALLERIES_FILEAPI_READAHEAD_FILE_STREAM_READER_H_
     63