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// 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 STORAGE_BROWSER_FILEAPI_FILE_STREAM_WRITER_H_
#define STORAGE_BROWSER_FILEAPI_FILE_STREAM_WRITER_H_
#include "base/basictypes.h"
#include "net/base/completion_callback.h"
#include "storage/browser/storage_browser_export.h"
namespace base {
class FilePath;
class TaskRunner;
}
namespace net {
class IOBuffer;
}
namespace storage {
// A generic interface for writing to a file-like object.
class FileStreamWriter {
public:
enum OpenOrCreate { OPEN_EXISTING_FILE, CREATE_NEW_FILE };
// Creates a writer for the existing file in the path |file_path| starting
// from |initial_offset|. Uses |task_runner| for async file operations.
STORAGE_EXPORT static FileStreamWriter* CreateForLocalFile(
base::TaskRunner* task_runner,
const base::FilePath& file_path,
int64 initial_offset,
OpenOrCreate open_or_create);
// 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 ~FileStreamWriter() {}
// 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.
//
// After the last write, Flush() must be called if the file system written to
// was registered with the FlushPolicy::FLUSH_ON_COMPLETION policy in mount
// options.
//
// This errors out (either synchronously or via callback) with:
// net::ERR_FILE_NOT_FOUND: When the target file is not found.
// net::ERR_ACCESS_DENIED: When the target file is a directory or
// the writer has no permission on the file.
// net::ERR_FILE_NO_SPACE: When the write will result in out of quota
// or there is not enough room left on the disk.
//
// 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.
//
// If the cancel is finished synchronously, it returns net::OK. If the
// cancel could not be performed, it returns an error code. Especially when
// there is no in-flight operation, net::ERR_UNEXPECTED is returned.
// Otherwise, net::ERR_IO_PENDING is returned, and the callback will be run on
// the thread where Cancel() was called when the cancel has completed. It is
// invalid to call Cancel() more than once on the same async operation.
//
// In either case, the callback function passed to the in-flight async
// operation is dismissed immediately when Cancel() is called, and thus
// will never be called.
virtual int Cancel(const net::CompletionCallback& callback) = 0;
// Flushes the data written so far.
//
// If the flush finished synchronously, it return net::OK. If the flush 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 Flush() was
// called when the flush has completed.
//
// It is invalid to call Flush while there is an in-flight async operation.
virtual int Flush(const net::CompletionCallback& callback) = 0;
};
} // namespace storage
#endif // STORAGE_BROWSER_FILEAPI_FILE_STREAM_WRITER_H_