fileapi: FileWriter and LocalFileWriter.

webkit/fileapi/file_writer.h

+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef WEBKIT_FILEAPI_FILE_WRITER_H_
+#define WEBKIT_FILEAPI_FILE_WRITER_H_
+#pragma once
+
+#include "base/basictypes.h"
+#include "net/base/completion_callback.h"
+#include "net/base/net_errors.h"
+
+namespace net {
+class IOBuffer;
+}
+
+namespace fileapi {
+
+// A generic interface for writing to a file-like object.
+class FileWriter {
+ public:
+  // Closes the file. If there's an in-flight operation, it is canceled (i.e.,
+  // the callback function associated with the operation is not called).
+  virtual ~FileWriter() {}
+
+  // Writes to the current cursor position asynchronously.
+  //
+  // Up to buf_len bytes will be written.  (In other words, partial
+  // writes are allowed.) If the write completed synchronously, it returns
+  // the number of bytes written. If the operation could not be performed, it
+  // returns an error code. Otherwise, net::ERR_IO_PENDING is returned, and the
+  // callback will be run on the thread where Write() was called when the write
+  // has completed.
+  //
+  // It is invalid to call Write while there is an in-flight async operation.
+  virtual int Write(net::IOBuffer* buf, int buf_len,
+                    const net::CompletionCallback& callback) = 0;
+
+  // Cancels an in-flight async operation (Write or Seek). When the cancel is
+  // done, |callback| is called. The callback function passed to the canceled
+  // async operation is not called.
+  //
+  // It is allowed to call Cancel when there's no active async operation. In
+  // that case, |callback| is called back with net::ERR_FAILED.

[kinuko, 2012/04/23 09:29:57]

ERR_UNEXPECTED?

Hmm on the second thought it might be better to just make this function return
an integer error code (as well as Write), and make it return ERR_UNEXPECTED if
we have no async operations or ERR_IO_PENDING if we have async operations and
do/can not cancel them immediately.

[kinaba, 2012/04/23 10:55:14]

Sounds much nicer! Done.

+  virtual void Cancel(const net::CompletionCallback& callback) = 0;
+};
+
+}  // namespace fileapi
+
+#endif  // WEBKIT_FILEAPI_FILE_WRITER_H_
+