xpcom/io/nsIAsyncInputStream.idl

   1 /* This Source Code Form is subject to the terms of the Mozilla Public
   2  * License, v. 2.0. If a copy of the MPL was not distributed with this
   3  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   4
   5 #include "nsIInputStream.idl"
   6
   7 interface nsIInputStreamCallback;
   8 interface nsIEventTarget;
   9
  10 /**
  11  * If an input stream is non-blocking, it may return NS_BASE_STREAM_WOULD_BLOCK
  12  * when read.  The caller must then wait for the stream to have some data to
  13  * read.  If the stream implements nsIAsyncInputStream, then the caller can use
  14  * this interface to request an asynchronous notification when the stream
  15  * becomes readable or closed (via the AsyncWait method).
  16  *
  17  * While this interface is almost exclusively used with non-blocking streams, it
  18  * is not necessary that nsIInputStream::isNonBlocking return true.  Nor is it
  19  * necessary that a non-blocking nsIInputStream implementation also implement
  20  * nsIAsyncInputStream.
  21  */
  22 [scriptable, builtinclass, uuid(a5f255ab-4801-4161-8816-277ac92f6ad1)]
  23 interface nsIAsyncInputStream : nsIInputStream
  24 {
  25     /**
  26      * This method closes the stream and sets its internal status.  If the
  27      * stream is already closed, then this method is ignored.  Once the stream
  28      * is closed, the stream's status cannot be changed.  Any successful status
  29      * code passed to this method is treated as NS_BASE_STREAM_CLOSED, which
  30      * has an effect equivalent to nsIInputStream::close.
  31      *
  32      * NOTE: this method exists in part to support pipes, which have both an
  33      * input end and an output end.  If the input end of a pipe is closed, then
  34      * writes to the output end of the pipe will fail.  The error code returned
  35      * when an attempt is made to write to a "broken" pipe corresponds to the
  36      * status code passed in when the input end of the pipe was closed, which
  37      * greatly simplifies working with pipes in some cases.
  38      *
  39      * @param aStatus
  40      *        The error that will be reported if this stream is accessed after
  41      *        it has been closed.
  42      */
  43     void closeWithStatus(in nsresult aStatus);
  44
  45     /**
  46      * Asynchronously wait for the stream to be readable or closed.  The
  47      * notification is one-shot, meaning that each asyncWait call will result
  48      * in exactly one notification callback.  After the OnInputStreamReady event
  49      * is dispatched, the stream releases its reference to the
  50      * nsIInputStreamCallback object.  It is safe to call asyncWait again from the
  51      * notification handler.
  52      *
  53      * This method may be called at any time (even if read has not been called).
  54      * In other words, this method may be called when the stream already has
  55      * data to read.  It may also be called when the stream is closed and will NOT
  56      * result in an error return, e.g., NS_BASE_STREAM_CLOSED.  If the stream is
  57      * already readable or closed when AsyncWait is called, then the
  58      * OnInputStreamReady event will be dispatched immediately.  Otherwise, the
  59      * event will be dispatched when the stream becomes readable or closed.
  60      *
  61      * @param aCallback
  62      *        This object is notified when the stream becomes ready.  This
  63      *        parameter may be null to clear an existing callback.
  64      * @param aFlags
  65      *        This parameter specifies optional flags passed in to configure
  66      *        the behavior of this method.  Pass zero to specify no flags.
  67      * @param aRequestedCount
  68      *        Wait until at least this many bytes can be read.  This is only
  69      *        a suggestion to the underlying stream; it may be ignored.  The
  70      *        caller may pass zero to indicate no preference.
  71      * @param aEventTarget
  72      *        Specify NULL to receive notification on ANY thread (possibly even
  73      *        recursively on the calling thread -- i.e., synchronously), or
  74      *        specify that the notification be delivered to a specific event
  75      *        target.
  76      */
  77     void asyncWait(in nsIInputStreamCallback aCallback,
  78                    in unsigned long aFlags,
  79                    in unsigned long aRequestedCount,
  80                    in nsIEventTarget aEventTarget);
  81
  82     /**
  83      * If passed to asyncWait, this flag overrides the default behavior,
  84      * causing the OnInputStreamReady notification to be suppressed until the
  85      * stream becomes closed (either as a result of closeWithStatus/close being
  86      * called on the stream or possibly due to some error in the underlying
  87      * stream).
  88      */
  89     const unsigned long WAIT_CLOSURE_ONLY = (1<<0);
  90 };
  91
  92 /**
  93  * This is a companion interface for nsIAsyncInputStream::asyncWait.
  94  */
  95 [function, scriptable, uuid(d1f28e94-3a6e-4050-a5f5-2e81b1fc2a43)]
  96 interface nsIInputStreamCallback : nsISupports
  97 {
  98     /**
  99      * Called to indicate that the stream is either readable or closed.
 100      *
 101      * @param aStream
 102      *        The stream whose asyncWait method was called.
 103      */
 104     void onInputStreamReady(in nsIAsyncInputStream aStream);
 105 };