chrome/browser/media_galleries/fileapi/readahead_file_stream_reader.h

   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/fileapi/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   ~ReadaheadFileStreamReader() override;
  22
  23   // FileStreamReader overrides.
  24   int Read(net::IOBuffer* buf,
  25            int buf_len,
  26            const net::CompletionCallback& callback) override;
  27   int64 GetLength(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_