1 files changed, 104 insertions, 0 deletions
diff --git a/xpcom/io/nsIAsyncOutputStream.idl b/xpcom/io/nsIAsyncOutputStream.idl
new file mode 100644
index 0000000000..a76200c249
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+++ b/xpcom/io/nsIAsyncOutputStream.idl
@@ -0,0 +1,104 @@
+/* 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 "nsIOutputStream.idl"
+
+interface nsIOutputStreamCallback;
+interface nsIEventTarget;
+
+/**
+ * If an output stream is non-blocking, it may return NS_BASE_STREAM_WOULD_BLOCK
+ * when written to.  The caller must then wait for the stream to become
+ * writable.  If the stream implements nsIAsyncOutputStream, then the caller can
+ * use this interface to request an asynchronous notification when the stream
+ * becomes writable or closed (via the AsyncWait method).
+ *
+ * While this interface is almost exclusively used with non-blocking streams, it
+ * is not necessary that nsIOutputStream::isNonBlocking return true.  Nor is it
+ * necessary that a non-blocking nsIOutputStream implementation also implement
+ * nsIAsyncOutputStream.
+ */
+[scriptable, uuid(beb632d3-d77a-4e90-9134-f9ece69e8200)]
+interface nsIAsyncOutputStream : nsIOutputStream
+{
+    /**
+     * 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
+     * is 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 output end of a pipe is closed, then
+     * reads from the input end of the pipe will fail.  The error code returned
+     * when an attempt is made to read from a "closed" pipe corresponds to the
+     * status code passed in when the output end of the pipe is 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 reason);
+
+    /**
+     * Asynchronously wait for the stream to be writable or closed.  The
+     * notification is one-shot, meaning that each asyncWait call will result
+     * in exactly one notification callback.  After the OnOutputStreamReady event
+     * is dispatched, the stream releases its reference to the
+     * nsIOutputStreamCallback object.  It is safe to call asyncWait again from the
+     * notification handler.
+     *
+     * This method may be called at any time (even if write has not been called).
+     * In other words, this method may be called when the stream already has
+     * room for more data.  It may also be called when the stream is closed.  If
+     * the stream is already writable or closed when AsyncWait is called, then the
+     * OnOutputStreamReady event will be dispatched immediately.  Otherwise, the
+     * event will be dispatched when the stream becomes writable 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 written.  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 nsIOutputStreamCallback aCallback,
+                   in unsigned long aFlags,
+                   in unsigned long aRequestedCount,
+                   in nsIEventTarget aEventTarget);
+
+    /**
+     * If passed to asyncWait, this flag overrides the default behavior,
+     * causing the OnOutputStreamReady 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 nsIAsyncOutputStream::asyncWait.
+ */
+[function, scriptable, uuid(40dbcdff-9053-42c5-a57c-3ec910d0f148)]
+interface nsIOutputStreamCallback : nsISupports
+{
+    /**
+     * Called to indicate that the stream is either writable or closed.
+     *
+     * @param aStream
+     *        The stream whose asyncWait method was called.
+     */
+    void onOutputStreamReady(in nsIAsyncOutputStream aStream);
+};