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// Copyright (c) 2008 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 FileInputStream, a basic interface for reading files
// synchronously or asynchronously with support for seeking to an offset.
#ifndef NET_BASE_FILE_INPUT_STREAM_H_
#define NET_BASE_FILE_INPUT_STREAM_H_
#include "net/base/completion_callback.h"
#if defined(OS_WIN)
typedef void* HANDLE;
#endif
namespace net {
// TODO(darin): Move this to a more generic location.
// This explicit mapping matches both FILE_ on Windows and SEEK_ on Linux.
enum Whence {
FROM_BEGIN = 0,
FROM_CURRENT = 1,
FROM_END = 2
};
class FileInputStream {
public:
FileInputStream();
~FileInputStream();
// Call this method to close the FileInputStream. It is OK to call Close
// multiple times. Redundant calls are ignored.
void Close();
// Call this method to open the FileInputStream. The remaining methods
// cannot be used unless this method returns OK. If the file cannot be
// opened then an error code is returned.
// NOTE: The underlying file is opened with non-exclusive access.
int Open(const std::wstring& path, bool asynchronous_mode);
// Returns true if Open succeeded and Close has not been called.
bool IsOpen() const;
// Adjust the position from where data is read. Upon success, the stream
// position relative to the start of the file is returned. Otherwise, an
// error code is returned. It is not valid to call Seek while a Read call
// has a pending completion.
int64 Seek(Whence whence, int64 offset);
// Returns the number of bytes available to read from the current stream
// position until the end of the file. Otherwise, an error code is returned.
int64 Available();
// Call this method to read data from the current stream position. 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.
//
// If opened with |asynchronous_mode| set to true, then a non-null callback
// must be passed to this method. In asynchronous mode, if the read could
// not complete synchronously, then ERR_IO_PENDING is returned, and the
// callback will be notified on the current thread (via the MessageLoop) when
// the read has completed.
//
// In the case of an asychronous read, the memory pointed to by |buf| must
// remain valid until the callback is notified. However, 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.
//
int Read(char* buf, int buf_len, CompletionCallback* callback);
private:
class AsyncContext;
friend class AsyncContext;
// This member is used to support asynchronous reads. It is non-null when
// the FileInputStream was opened with asynchronous_mode set to true.
scoped_ptr<AsyncContext> async_context_;
#if defined(OS_WIN)
HANDLE handle_;
#elif defined(OS_POSIX)
int fd_;
#endif
DISALLOW_COPY_AND_ASSIGN(FileInputStream);
};
} // namespace net
#endif // NET_BASE_FILE_INPUT_STREAM_H_
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