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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);
+};