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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).
~FileStreamWriter()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   // This errors out (either synchronously or via callback) with:
50   //   net::ERR_FILE_NOT_FOUND: When the target file is not found.
51   //   net::ERR_ACCESS_DENIED: When the target file is a directory or
52   //      the writer has no permission on the file.
53   //   net::ERR_FILE_NO_SPACE: When the write will result in out of quota
54   //      or there is not enough room left on the disk.
55   //
56   // It is invalid to call Write while there is an in-flight async operation.
57   virtual int Write(net::IOBuffer* buf, int buf_len,
58                     const net::CompletionCallback& callback) = 0;
59 
60   // Cancels an in-flight async operation.
61   //
62   // If the cancel is finished synchronously, it returns net::OK. If the
63   // cancel could not be performed, it returns an error code. Especially when
64   // there is no in-flight operation, net::ERR_UNEXPECTED is returned.
65   // Otherwise, net::ERR_IO_PENDING is returned, and the callback will be run on
66   // the thread where Cancel() was called when the cancel has completed. It is
67   // invalid to call Cancel() more than once on the same async operation.
68   //
69   // In either case, the callback function passed to the in-flight async
70   // operation is dismissed immediately when Cancel() is called, and thus
71   // will never be called.
72   virtual int Cancel(const net::CompletionCallback& callback) = 0;
73 
74   // Flushes the data written so far.
75   //
76   // If the flush finished synchronously, it return net::OK. If the flush could
77   // not be performed, it returns an error code. Otherwise, net::ERR_IO_PENDING
78   // is returned, and the callback will be run on the thread where Flush() was
79   // called when the flush has completed.
80   //
81   // It is invalid to call Flush while there is an in-flight async operation.
82   virtual int Flush(const net::CompletionCallback& callback) = 0;
83 };
84 
85 }  // namespace storage
86 
87 #endif  // STORAGE_BROWSER_FILEAPI_FILE_STREAM_WRITER_H_
88