michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #include "nsIOutputStream.idl"
michael@0: 
michael@0: interface nsIOutputStreamCallback;
michael@0: interface nsIEventTarget;
michael@0: 
michael@0: /**
michael@0:  * If an output stream is non-blocking, it may return NS_BASE_STREAM_WOULD_BLOCK
michael@0:  * when written to.  The caller must then wait for the stream to become
michael@0:  * writable.  If the stream implements nsIAsyncOutputStream, then the caller can
michael@0:  * use this interface to request an asynchronous notification when the stream
michael@0:  * becomes writable or closed (via the AsyncWait method).
michael@0:  *
michael@0:  * While this interface is almost exclusively used with non-blocking streams, it
michael@0:  * is not necessary that nsIOutputStream::isNonBlocking return true.  Nor is it
michael@0:  * necessary that a non-blocking nsIOutputStream implementation also implement
michael@0:  * nsIAsyncOutputStream.
michael@0:  */
michael@0: [scriptable, uuid(beb632d3-d77a-4e90-9134-f9ece69e8200)]
michael@0: interface nsIAsyncOutputStream : nsIOutputStream
michael@0: {
michael@0:     /**
michael@0:      * This method closes the stream and sets its internal status.  If the 
michael@0:      * stream is already closed, then this method is ignored.  Once the stream
michael@0:      * is closed, the stream's status cannot be changed.  Any successful status
michael@0:      * code passed to this method is treated as NS_BASE_STREAM_CLOSED, which
michael@0:      * is equivalent to nsIInputStream::close. 
michael@0:      *
michael@0:      * NOTE: this method exists in part to support pipes, which have both an 
michael@0:      * input end and an output end.  If the output end of a pipe is closed, then
michael@0:      * reads from the input end of the pipe will fail.  The error code returned 
michael@0:      * when an attempt is made to read from a "closed" pipe corresponds to the
michael@0:      * status code passed in when the output end of the pipe is closed, which
michael@0:      * greatly simplifies working with pipes in some cases.
michael@0:      *
michael@0:      * @param aStatus
michael@0:      *        The error that will be reported if this stream is accessed after
michael@0:      *        it has been closed.
michael@0:      */
michael@0:     void closeWithStatus(in nsresult reason);
michael@0: 
michael@0:     /**
michael@0:      * Asynchronously wait for the stream to be writable or closed.  The
michael@0:      * notification is one-shot, meaning that each asyncWait call will result
michael@0:      * in exactly one notification callback.  After the OnOutputStreamReady event
michael@0:      * is dispatched, the stream releases its reference to the 
michael@0:      * nsIOutputStreamCallback object.  It is safe to call asyncWait again from the
michael@0:      * notification handler.
michael@0:      *
michael@0:      * This method may be called at any time (even if write has not been called).
michael@0:      * In other words, this method may be called when the stream already has
michael@0:      * room for more data.  It may also be called when the stream is closed.  If
michael@0:      * the stream is already writable or closed when AsyncWait is called, then the
michael@0:      * OnOutputStreamReady event will be dispatched immediately.  Otherwise, the
michael@0:      * event will be dispatched when the stream becomes writable or closed.
michael@0:      * 
michael@0:      * @param aCallback
michael@0:      *        This object is notified when the stream becomes ready.  This
michael@0:      *        parameter may be null to clear an existing callback.
michael@0:      * @param aFlags
michael@0:      *        This parameter specifies optional flags passed in to configure
michael@0:      *        the behavior of this method.  Pass zero to specify no flags.
michael@0:      * @param aRequestedCount
michael@0:      *        Wait until at least this many bytes can be written.  This is only
michael@0:      *        a suggestion to the underlying stream; it may be ignored.  The
michael@0:      *        caller may pass zero to indicate no preference.
michael@0:      * @param aEventTarget
michael@0:      *        Specify NULL to receive notification on ANY thread (possibly even
michael@0:      *        recursively on the calling thread -- i.e., synchronously), or
michael@0:      *        specify that the notification be delivered to a specific event
michael@0:      *        target.
michael@0:      */
michael@0:     void asyncWait(in nsIOutputStreamCallback aCallback,
michael@0:                    in unsigned long aFlags,
michael@0:                    in unsigned long aRequestedCount,
michael@0:                    in nsIEventTarget aEventTarget);
michael@0: 
michael@0:     /**
michael@0:      * If passed to asyncWait, this flag overrides the default behavior,
michael@0:      * causing the OnOutputStreamReady notification to be suppressed until the
michael@0:      * stream becomes closed (either as a result of closeWithStatus/close being
michael@0:      * called on the stream or possibly due to some error in the underlying
michael@0:      * stream).
michael@0:      */
michael@0:     const unsigned long WAIT_CLOSURE_ONLY = (1<<0);
michael@0: };
michael@0: 
michael@0: /**
michael@0:  * This is a companion interface for nsIAsyncOutputStream::asyncWait.
michael@0:  */
michael@0: [scriptable, uuid(40dbcdff-9053-42c5-a57c-3ec910d0f148)]
michael@0: interface nsIOutputStreamCallback : nsISupports
michael@0: {
michael@0:     /**
michael@0:      * Called to indicate that the stream is either writable or closed.
michael@0:      *
michael@0:      * @param aStream
michael@0:      *        The stream whose asyncWait method was called.
michael@0:      */
michael@0:     void onOutputStreamReady(in nsIAsyncOutputStream aStream);
michael@0: };