storage/browser/fileapi/file_stream_writer.h

   1 // Copyright (c) 2012 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 STORAGE_BROWSER_FILEAPI_FILE_STREAM_WRITER_H_
   6 #define STORAGE_BROWSER_FILEAPI_FILE_STREAM_WRITER_H_
   7
   8 #include "base/basictypes.h"
   9 #include "net/base/completion_callback.h"
  10 #include "storage/browser/storage_browser_export.h"
  11
  12 namespace base {
  13 class FilePath;
  14 class TaskRunner;
  15 }
  16
  17 namespace net {
  18 class IOBuffer;
  19 }
  20
  21 namespace storage {
  22
  23 // A generic interface for writing to a file-like object.
  24 class FileStreamWriter {
  25  public:
  26   enum OpenOrCreate { OPEN_EXISTING_FILE, CREATE_NEW_FILE };
  27
  28   // Creates a writer for the existing file in the path |file_path| starting
  29   // from |initial_offset|. Uses |task_runner| for async file operations.
  30   STORAGE_EXPORT static FileStreamWriter* CreateForLocalFile(
  31       base::TaskRunner* task_runner,
  32       const base::FilePath& file_path,
  33       int64 initial_offset,
  34       OpenOrCreate open_or_create);
  35
  36   // Closes the file. If there's an in-flight operation, it is canceled (i.e.,
  37   // the callback function associated with the operation is not called).
  38   virtual ~FileStreamWriter() {}
  39
  40   // Writes to the current cursor position asynchronously.
  41   //
  42   // Up to buf_len bytes will be written.  (In other words, partial
  43   // writes are allowed.) If the write completed synchronously, it returns
  44   // the number of bytes written. If the operation could not be performed, it
  45   // returns an error code. Otherwise, net::ERR_IO_PENDING is returned, and the
  46   // callback will be run on the thread where Write() was called when the write
  47   // has completed.
  48   //
  49   // After the last write, Flush() must be called if the file system written to
  50   // was registered with the FlushPolicy::FLUSH_ON_COMPLETION policy in mount
  51   // options.
  52   //
  53   // This errors out (either synchronously or via callback) with:
  54   //   net::ERR_FILE_NOT_FOUND: When the target file is not found.
  55   //   net::ERR_ACCESS_DENIED: When the target file is a directory or
  56   //      the writer has no permission on the file.
  57   //   net::ERR_FILE_NO_SPACE: When the write will result in out of quota
  58   //      or there is not enough room left on the disk.
  59   //
  60   // It is invalid to call Write while there is an in-flight async operation.
  61   virtual int Write(net::IOBuffer* buf, int buf_len,
  62                     const net::CompletionCallback& callback) = 0;
  63
  64   // Cancels an in-flight async operation.
  65   //
  66   // If the cancel is finished synchronously, it returns net::OK. If the
  67   // cancel could not be performed, it returns an error code. Especially when
  68   // there is no in-flight operation, net::ERR_UNEXPECTED is returned.
  69   // Otherwise, net::ERR_IO_PENDING is returned, and the callback will be run on
  70   // the thread where Cancel() was called when the cancel has completed. It is
  71   // invalid to call Cancel() more than once on the same async operation.
  72   //
  73   // In either case, the callback function passed to the in-flight async
  74   // operation is dismissed immediately when Cancel() is called, and thus
  75   // will never be called.
  76   virtual int Cancel(const net::CompletionCallback& callback) = 0;
  77
  78   // Flushes the data written so far.
  79   //
  80   // If the flush finished synchronously, it return net::OK. If the flush could
  81   // not be performed, it returns an error code. Otherwise, net::ERR_IO_PENDING
  82   // is returned, and the callback will be run on the thread where Flush() was
  83   // called when the flush has completed.
  84   //
  85   // It is invalid to call Flush while there is an in-flight async operation.
  86   virtual int Flush(const net::CompletionCallback& callback) = 0;
  87 };
  88
  89 }  // namespace storage
  90
  91 #endif  // STORAGE_BROWSER_FILEAPI_FILE_STREAM_WRITER_H_