chrome/browser/chromeos/file_system_provider/fileapi/buffering_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_CHROMEOS_FILE_SYSTEM_PROVIDER_FILEAPI_BUFFERING_FILE_STREAM_READER_H_
   6 #define CHROME_BROWSER_CHROMEOS_FILE_SYSTEM_PROVIDER_FILEAPI_BUFFERING_FILE_STREAM_READER_H_
   7
   8 #include "base/basictypes.h"
   9 #include "base/memory/ref_counted.h"
  10 #include "base/memory/scoped_ptr.h"
  11 #include "base/memory/weak_ptr.h"
  12 #include "storage/browser/fileapi/file_stream_reader.h"
  13
  14 namespace net {
  15 class IOBuffer;
  16 }  // namespace net
  17
  18 namespace chromeos {
  19 namespace file_system_provider {
  20
  21 // Wraps the file stream reader implementation with a prefetching buffer.
  22 // Reads data from the internal file stream reader in chunks of size at least
  23 // |preloading_buffer_length| bytes (or less for the last chunk, because of
  24 // EOF). Up to |max_bytes_to_read| of bytes can be requested in total.
  25 //
  26 // The underlying internal file stream reader *must not* return any values
  27 // synchronously. Instead, results must be returned by a callback, including
  28 // errors.
  29 class BufferingFileStreamReader : public storage::FileStreamReader {
  30  public:
  31   BufferingFileStreamReader(
  32       scoped_ptr<storage::FileStreamReader> file_stream_reader,
  33       int preloading_buffer_length,
  34       int64 max_bytes_to_read);
  35
  36   ~BufferingFileStreamReader() override;
  37
  38   // storage::FileStreamReader overrides.
  39   int Read(net::IOBuffer* buf,
  40            int buf_len,
  41            const net::CompletionCallback& callback) override;
  42   int64 GetLength(const net::Int64CompletionCallback& callback) override;
  43
  44  private:
  45   // Copies data from the preloading buffer and updates the internal iterator.
  46   // Returns number of bytes successfully copied.
  47   int CopyFromPreloadingBuffer(scoped_refptr<net::IOBuffer> buffer,
  48                                int buffer_length);
  49
  50   // Preloads data from the internal stream reader and calls the |callback|.
  51   void Preload(const net::CompletionCallback& callback);
  52
  53   void OnReadCompleted(const net::CompletionCallback& callback, int result);
  54
  55   // Called when preloading of a buffer chunk is finished. Updates state of the
  56   // preloading buffer and copied requested data to the |buffer|.
  57   void OnPreloadCompleted(scoped_refptr<net::IOBuffer> buffer,
  58                           int buffer_length,
  59                           const net::CompletionCallback& callback,
  60                           int result);
  61
  62   scoped_ptr<storage::FileStreamReader> file_stream_reader_;
  63   int preloading_buffer_length_;
  64   int64 max_bytes_to_read_;
  65   int64 bytes_read_;
  66   scoped_refptr<net::IOBuffer> preloading_buffer_;
  67   int preloading_buffer_offset_;
  68   int preloaded_bytes_;
  69
  70   base::WeakPtrFactory<BufferingFileStreamReader> weak_ptr_factory_;
  71   DISALLOW_COPY_AND_ASSIGN(BufferingFileStreamReader);
  72 };
  73
  74 }  // namespace file_system_provider
  75 }  // namespace chromeos
  76
  77 #endif  // CHROME_BROWSER_CHROMEOS_FILE_SYSTEM_PROVIDER_FILEAPI_BUFFERING_FILE_STREAM_READER_H_