gecko-dev/xpcom/io/nsISafeOutputStream.idl

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "nsISupports.idl"

/**
 * This interface provides a mechanism to control an output stream
 * that takes care not to overwrite an existing target until it is known
 * that all writes to the destination succeeded.
 * 
 * An object that supports this interface is intended to also support
 * nsIOutputStream.
 *
 * For example, a file output stream that supports this interface writes to
 * a temporary file, and moves it over the original file when |finish| is
 * called only if the stream can be successfully closed and all writes
 * succeeded.  If |finish| is called but something went wrong during
 * writing, it will delete the temporary file and not touch the original.
 * If the stream is closed by calling |close| directly, or the stream
 * goes away, the original file will not be overwritten, and the temporary
 * file will be deleted.
 *
 * Currently, this interface is implemented only for file output streams.
 */
[scriptable, uuid(5f914307-5c34-4e1f-8e32-ec749d25b27a)]
interface nsISafeOutputStream : nsISupports
{
    /**
     * Call this method to close the stream and cause the original target
     * to be overwritten. Note: if any call to |write| failed to write out
     * all of the data given to it, then calling this method will |close| the
     * stream and return failure. Further, if closing the stream fails, this
     * method will return failure. The original target will be overwritten only
     * if all calls to |write| succeeded and the stream was successfully closed.
     */
    void finish();
};