webkit/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 WEBKIT_FILEAPI_FILE_STREAM_WRITER_H_
   6 #define WEBKIT_FILEAPI_FILE_STREAM_WRITER_H_
   7
   8 #include "base/basictypes.h"
   9 #include "net/base/completion_callback.h"
  10 #include "webkit/fileapi/fileapi_export.h"
  11
  12 namespace net {
  13 class IOBuffer;
  14 }
  15
  16 namespace fileapi {
  17
  18 // A generic interface for writing to a file-like object.
  19 class FILEAPI_EXPORT_PRIVATE FileStreamWriter {
  20  public:
  21   // Closes the file. If there's an in-flight operation, it is canceled (i.e.,
  22   // the callback function associated with the operation is not called).
  23   virtual ~FileStreamWriter() {}
  24
  25   // Writes to the current cursor position asynchronously.
  26   //
  27   // Up to buf_len bytes will be written.  (In other words, partial
  28   // writes are allowed.) If the write completed synchronously, it returns
  29   // the number of bytes written. If the operation could not be performed, it
  30   // returns an error code. Otherwise, net::ERR_IO_PENDING is returned, and the
  31   // callback will be run on the thread where Write() was called when the write
  32   // has completed.
  33   //
  34   // This errors out (either synchronously or via callback) with:
  35   //   net::ERR_FILE_NOT_FOUND: When the target file is not found.
  36   //   net::ERR_ACCESS_DENIED: When the target file is a directory or
  37   //      the writer has no permission on the file.
  38   //   net::ERR_FILE_NO_SPACE: When the write will result in out of quota
  39   //      or there is not enough room left on the disk.
  40   //
  41   // It is invalid to call Write while there is an in-flight async operation.
  42   virtual int Write(net::IOBuffer* buf, int buf_len,
  43                     const net::CompletionCallback& callback) = 0;
  44
  45   // Cancels an in-flight async operation.
  46   //
  47   // If the cancel is finished synchronously, it returns net::OK. If the
  48   // cancel could not be performed, it returns an error code. Especially when
  49   // there is no in-flight operation, net::ERR_UNEXPECTED is returned.
  50   // Otherwise, net::ERR_IO_PENDING is returned, and the callback will be run on
  51   // the thread where Cancel() was called when the cancel has completed. It is
  52   // invalid to call Cancel() more than once on the same async operation.
  53   //
  54   // In either case, the callback function passed to the in-flight async
  55   // operation is dismissed immediately when Cancel() is called, and thus
  56   // will never be called.
  57   virtual int Cancel(const net::CompletionCallback& callback) = 0;
  58 };
  59
  60 }  // namespace fileapi
  61
  62 #endif  // WEBKIT_FILEAPI_FILE_STREAM_WRITER_H_