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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 "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);
};