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.
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.
| aStatus | The error that will be reported if this stream is accessed after it has been closed. |
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.
| aCallback | This object is notified when the stream becomes ready. This parameter may be null to clear an existing callback. |
| aFlags | This parameter specifies optional flags passed in to configure the behavior of this method. Pass zero to specify no flags. |
| 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. |
| 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. |
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).