nsIAsyncInputStream

IID:15a15329-00de-44e8-ab06-0d0b0d43dc5b
Inherits From:nsIInputStream

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.


Constants

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).
PRUint32 WAIT_CLOSURE_ONLY = 1

Methods

void asyncWait ( nsIInputStreamCallback callback , PRUint32 flags , PRUint32 requestedCount , nsIEventTarget eventTarget ) void closeWithStatus ( nsresult status )

void asyncWait ( nsIInputStreamCallback callback , PRUint32 flags , PRUint32 requestedCount , nsIEventTarget eventTarget )

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.

Arguments:
callback: This object is notified when the stream becomes ready.
flags: This parameter specifies optional flags passed in to configure the behavior of this method. Pass zero to specify no flags.
requestedCount: 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.
eventTarget: 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 closeWithStatus ( nsresult status )

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.

Arguments:
status: The error that will be reported if this stream is accessed after it has been closed.

References

This interface is the type of the following properties:

nsIPipe.inputStream

This interface is passed as an argument to the following methods:

nsIInputStreamCallback.onInputStreamReady

Reference documentation is generated from Mozilla's source.

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