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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.
// This file defines FileStream, a basic interface for reading and writing files
// synchronously or asynchronously with support for seeking to an offset.
// Note that even when used asynchronously, only one operation is supported at
// a time.
#ifndef NET_BASE_FILE_STREAM_H_
#define NET_BASE_FILE_STREAM_H_
#include <stdint.h>
#include "base/files/file.h"
#include "base/macros.h"
#include "net/base/completion_callback.h"
#include "net/base/net_export.h"
namespace base {
class FilePath;
class TaskRunner;
}
namespace net {
class IOBuffer;
class NET_EXPORT FileStream {
public:
// Creates a FileStream.
// Uses |task_runner| for asynchronous operations.
explicit FileStream(const scoped_refptr<base::TaskRunner>& task_runner);
// Construct a FileStream with an existing valid |file|.
// Uses |task_runner| for asynchronous operations.
FileStream(base::File file,
const scoped_refptr<base::TaskRunner>& task_runner);
// The underlying file is closed automatically.
virtual ~FileStream();
// Call this method to open the FileStream asynchronously. The remaining
// methods cannot be used unless the file is opened successfully. Returns
// ERR_IO_PENDING if the operation is started. If the operation cannot be
// started then an error code is returned.
//
// Once the operation is done, |callback| will be run on the thread where
// Open() was called, with the result code. open_flags is a bitfield of
// base::File::Flags.
//
// If the file stream is not closed manually, the underlying file will be
// automatically closed when FileStream is destructed in an asynchronous
// manner (i.e. the file stream is closed in the background but you don't
// know when).
virtual int Open(const base::FilePath& path, int open_flags,
const CompletionCallback& callback);
// Returns ERR_IO_PENDING and closes the file asynchronously, calling
// |callback| when done.
// It is invalid to request any asynchronous operations while there is an
// in-flight asynchronous operation.
virtual int Close(const CompletionCallback& callback);
// Returns true if Open succeeded and Close has not been called.
virtual bool IsOpen() const;
// Adjust the position from the start of the file where data is read
// asynchronously. Upon success, ERR_IO_PENDING is returned and |callback|
// will be run on the thread where Seek() was called with the the stream
// position relative to the start of the file. Otherwise, an error code is
// returned. It is invalid to request any asynchronous operations while there
// is an in-flight asynchronous operation.
virtual int Seek(int64_t offset, const Int64CompletionCallback& callback);
// Call this method to read data from the current stream position
// asynchronously. Up to buf_len bytes will be copied into buf. (In
// other words, partial reads are allowed.) Returns the number of bytes
// copied, 0 if at end-of-file, or an error code if the operation could
// not be performed.
//
// The file must be opened with FLAG_ASYNC, and a non-null
// callback must be passed to this method. If the read could not
// complete synchronously, then ERR_IO_PENDING is returned, and the
// callback will be run on the thread where Read() was called, when the
// read has completed.
//
// It is valid to destroy or close the file stream while there is an
// asynchronous read in progress. That will cancel the read and allow
// the buffer to be freed.
//
// It is invalid to request any asynchronous operations while there is an
// in-flight asynchronous operation.
//
// This method must not be called if the stream was opened WRITE_ONLY.
virtual int Read(IOBuffer* buf, int buf_len,
const CompletionCallback& callback);
// Call this method to write data at the current stream position
// asynchronously. Up to buf_len bytes will be written from buf. (In
// other words, partial writes are allowed.) Returns the number of
// bytes written, or an error code if the operation could not be
// performed.
//
// The file must be opened with FLAG_ASYNC, and a non-null
// callback must be passed to this method. If the write could not
// complete synchronously, then 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 valid to destroy or close the file stream while there is an
// asynchronous write in progress. That will cancel the write and allow
// the buffer to be freed.
//
// It is invalid to request any asynchronous operations while there is an
// in-flight asynchronous operation.
//
// This method must not be called if the stream was opened READ_ONLY.
//
// Zero byte writes are not allowed.
virtual int Write(IOBuffer* buf, int buf_len,
const CompletionCallback& callback);
// Forces out a filesystem sync on this file to make sure that the file was
// written out to disk and is not currently sitting in the buffer. This does
// not have to be called, it just forces one to happen at the time of
// calling.
//
// The file must be opened with FLAG_ASYNC, and a non-null
// callback must be passed to this method. If the write could not
// complete synchronously, then ERR_IO_PENDING is returned, and the
// callback will be run on the thread where Flush() was called when
// the write has completed.
//
// It is valid to destroy or close the file stream while there is an
// asynchronous flush in progress. That will cancel the flush and allow
// the buffer to be freed.
//
// It is invalid to request any asynchronous operations while there is an
// in-flight asynchronous operation.
//
// This method should not be called if the stream was opened READ_ONLY.
virtual int Flush(const CompletionCallback& callback);
private:
class Context;
// Context performing I/O operations. It was extracted into a separate class
// to perform asynchronous operations because FileStream can be destroyed
// before completion of an async operation. Also if a FileStream is destroyed
// without explicitly calling Close, the file should be closed asynchronously
// without delaying FileStream's destructor.
scoped_ptr<Context> context_;
DISALLOW_COPY_AND_ASSIGN(FileStream);
};
} // namespace net
#endif // NET_BASE_FILE_STREAM_H_
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