xpcom/io/nsIAsyncOutputStream.idl

   1 /* ***** BEGIN LICENSE BLOCK *****
   2  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
   3  *
   4  * The contents of this file are subject to the Mozilla Public License Version
   5  * 1.1 (the "License"); you may not use this file except in compliance with
   6  * the License. You may obtain a copy of the License at
   7  * http://www.mozilla.org/MPL/
   8  *
   9  * Software distributed under the License is distributed on an "AS IS" basis,
  10  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
  11  * for the specific language governing rights and limitations under the
  12  * License.
  13  *
  14  * The Original Code is Mozilla.
  15  *
  16  * The Initial Developer of the Original Code is
  17  * Netscape Communications Corporation.
  18  * Portions created by the Initial Developer are Copyright (C) 2002
  19  * the Initial Developer. All Rights Reserved.
  20  *
  21  * Contributor(s):
  22  *   Darin Fisher <darin@netscape.com>
  23  *
  24  * Alternatively, the contents of this file may be used under the terms of
  25  * either the GNU General Public License Version 2 or later (the "GPL"), or
  26  * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
  27  * in which case the provisions of the GPL or the LGPL are applicable instead
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  33  * the provisions above, a recipient may use your version of this file under
  34  * the terms of any one of the MPL, the GPL or the LGPL.
  35  *
  36  * ***** END LICENSE BLOCK ***** */
  37
  38 #include "nsIOutputStream.idl"
  39
  40 interface nsIOutputStreamCallback;
  41 interface nsIEventTarget;
  42
  43 /**
  44  * If an output stream is non-blocking, it may return NS_BASE_STREAM_WOULD_BLOCK
  45  * when written to.  The caller must then wait for the stream to become
  46  * writable.  If the stream implements nsIAsyncOutputStream, then the caller can
  47  * use this interface to request an asynchronous notification when the stream
  48  * becomes writable or closed (via the AsyncWait method).
  49  *
  50  * While this interface is almost exclusively used with non-blocking streams, it
  51  * is not necessary that nsIOutputStream::isNonBlocking return true.  Nor is it
  52  * necessary that a non-blocking nsIOutputStream implementation also implement
  53  * nsIAsyncOutputStream.
  54  */
  55 [scriptable, uuid(beb632d3-d77a-4e90-9134-f9ece69e8200)]
  56 interface nsIAsyncOutputStream : nsIOutputStream
  57 {
  58     /**
  59      * This method closes the stream and sets its internal status.  If the
  60      * stream is already closed, then this method is ignored.  Once the stream
  61      * is closed, the stream's status cannot be changed.  Any successful status
  62      * code passed to this method is treated as NS_BASE_STREAM_CLOSED, which
  63      * is equivalent to nsIInputStream::close.
  64      *
  65      * NOTE: this method exists in part to support pipes, which have both an
  66      * input end and an output end.  If the output end of a pipe is closed, then
  67      * reads from the input end of the pipe will fail.  The error code returned
  68      * when an attempt is made to read from a "closed" pipe corresponds to the
  69      * status code passed in when the output end of the pipe is closed, which
  70      * greatly simplifies working with pipes in some cases.
  71      *
  72      * @param aStatus
  73      *        The error that will be reported if this stream is accessed after
  74      *        it has been closed.
  75      */
  76     void closeWithStatus(in nsresult reason);
  77
  78     /**
  79      * Asynchronously wait for the stream to be writable or closed.  The
  80      * notification is one-shot, meaning that each asyncWait call will result
  81      * in exactly one notification callback.  After the OnOutputStreamReady event
  82      * is dispatched, the stream releases its reference to the
  83      * nsIOutputStreamCallback object.  It is safe to call asyncWait again from the
  84      * notification handler.
  85      *
  86      * This method may be called at any time (even if write has not been called).
  87      * In other words, this method may be called when the stream already has
  88      * room for more data.  It may also be called when the stream is closed.  If
  89      * the stream is already writable or closed when AsyncWait is called, then the
  90      * OnOutputStreamReady event will be dispatched immediately.  Otherwise, the
  91      * event will be dispatched when the stream becomes writable or closed.
  92      *
  93      * @param aCallback
  94      *        This object is notified when the stream becomes ready.  This
  95      *        parameter may be null to clear an existing callback.
  96      * @param aFlags
  97      *        This parameter specifies optional flags passed in to configure
  98      *        the behavior of this method.  Pass zero to specify no flags.
  99      * @param aRequestedCount
 100      *        Wait until at least this many bytes can be written.  This is only
 101      *        a suggestion to the underlying stream; it may be ignored.  The
 102      *        caller may pass zero to indicate no preference.
 103      * @param aEventTarget
 104      *        Specify NULL to receive notification on ANY thread (possibly even
 105      *        recursively on the calling thread -- i.e., synchronously), or
 106      *        specify that the notification be delivered to a specific event
 107      *        target.
 108      */
 109     void asyncWait(in nsIOutputStreamCallback aCallback,
 110                    in unsigned long aFlags,
 111                    in unsigned long aRequestedCount,
 112                    in nsIEventTarget aEventTarget);
 113
 114     /**
 115      * If passed to asyncWait, this flag overrides the default behavior,
 116      * causing the OnOutputStreamReady notification to be suppressed until the
 117      * stream becomes closed (either as a result of closeWithStatus/close being
 118      * called on the stream or possibly due to some error in the underlying
 119      * stream).
 120      */
 121     const unsigned long WAIT_CLOSURE_ONLY = (1<<0);
 122 };
 123
 124 /**
 125  * This is a companion interface for nsIAsyncOutputStream::asyncWait.
 126  */
 127 [scriptable, uuid(40dbcdff-9053-42c5-a57c-3ec910d0f148)]
 128 interface nsIOutputStreamCallback : nsISupports
 129 {
 130     /**
 131      * Called to indicate that the stream is either writable or closed.
 132      *
 133      * @param aStream
 134      *        The stream whose asyncWait method was called.
 135      */
 136     void onOutputStreamReady(in nsIAsyncOutputStream aStream);
 137 };