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 /* 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 "nsIInputStream.idl"

 interface nsIInputStreamCallback;

 interface nsIEventTarget;

 /**

  * If an input stream is non-blocking, it may return NS_BASE_STREAM_WOULD_BLOCK

  * when read.  The caller must then wait for the stream to have some data to 

  * read.  If the stream implements nsIAsyncInputStream, then the caller can use 

  * this interface to request an asynchronous notification when the stream

  * becomes readable or closed (via the AsyncWait method).

  *

  * While this interface is almost exclusively used with non-blocking streams, it

  * is not necessary that nsIInputStream::isNonBlocking return true.  Nor is it

  * necessary that a non-blocking nsIInputStream implementation also implement

  * nsIAsyncInputStream.

  */

 [scriptable, uuid(a5f255ab-4801-4161-8816-277ac92f6ad1)]

 interface nsIAsyncInputStream : nsIInputStream

 {

     /**

      * This method closes the stream and sets its internal status.  If the 

      * stream is already closed, then this method is ignored.  Once the stream

      * is closed, the stream's status cannot be changed.  Any successful status

      * code passed to this method is treated as NS_BASE_STREAM_CLOSED, which

      * has an effect equivalent to nsIInputStream::close. 

      *

      * NOTE: this method exists in part to support pipes, which have both an 

      * input end and an output end.  If the input end of a pipe is closed, then

      * writes to the output end of the pipe will fail.  The error code returned 

      * when an attempt is made to write to a "broken" pipe corresponds to the

      * status code passed in when the input end of the pipe was closed, which

      * greatly simplifies working with pipes in some cases.

      *

      * @param aStatus

      *        The error that will be reported if this stream is accessed after

      *        it has been closed.

      */

     void closeWithStatus(in nsresult aStatus);

     /**

      * Asynchronously wait for the stream to be readable or closed.  The

      * notification is one-shot, meaning that each asyncWait call will result

      * in exactly one notification callback.  After the OnInputStreamReady event

      * is dispatched, the stream releases its reference to the 

      * nsIInputStreamCallback object.  It is safe to call asyncWait again from the

      * notification handler.

      *

      * This method may be called at any time (even if read has not been called).

      * In other words, this method may be called when the stream already has

      * data to read.  It may also be called when the stream is closed.  If the

      * stream is already readable or closed when AsyncWait is called, then the

      * OnInputStreamReady event will be dispatched immediately.  Otherwise, the

      * event will be dispatched when the stream becomes readable or closed.

      * 

      * @param aCallback

      *        This object is notified when the stream becomes ready.  This

      *        parameter may be null to clear an existing callback.

      * @param aFlags

      *        This parameter specifies optional flags passed in to configure

      *        the behavior of this method.  Pass zero to specify no flags.

      * @param aRequestedCount

      *        Wait until at least this many bytes can be read.  This is only

      *        a suggestion to the underlying stream; it may be ignored.  The

      *        caller may pass zero to indicate no preference.

      * @param aEventTarget

      *        Specify NULL to receive notification on ANY thread (possibly even

      *        recursively on the calling thread -- i.e., synchronously), or

      *        specify that the notification be delivered to a specific event

      *        target.

      */

     void asyncWait(in nsIInputStreamCallback aCallback,

                    in unsigned long aFlags,

                    in unsigned long aRequestedCount,

                    in nsIEventTarget aEventTarget);

     /**

      * If passed to asyncWait, this flag overrides the default behavior,

      * causing the OnInputStreamReady notification to be suppressed until the

      * stream becomes closed (either as a result of closeWithStatus/close being

      * called on the stream or possibly due to some error in the underlying

      * stream).

      */

     const unsigned long WAIT_CLOSURE_ONLY = (1<<0);

 };

 /**

  * This is a companion interface for nsIAsyncInputStream::asyncWait.

  */

 [function, scriptable, uuid(d1f28e94-3a6e-4050-a5f5-2e81b1fc2a43)]

 interface nsIInputStreamCallback : nsISupports

 {

     /**

      * Called to indicate that the stream is either readable or closed.

      *

      * @param aStream

      *        The stream whose asyncWait method was called.

      */

     void onInputStreamReady(in nsIAsyncInputStream aStream);

 };