nsIProgressEventSink

This interface is used to asynchronously convey channel status and progress
information that is generally not critical to the processing of the channel.
The information is intended to be displayed to the user in some meaningful
way.

An implementation of this interface can be passed to a channel via the
channel’s notificationCallbacks attribute. See nsIChannel for more info.

The channel will begin passing notifications to the progress event sink
after its asyncOpen method has been called. Notifications will cease once
the channel calls its listener’s onStopRequest method or once the channel
is canceled (via nsIRequest::cancel).

NOTE: This interface is actually not specific to channels and may be used
with other implementations of nsIRequest.

Methods

onProgress(aRequest, aContext, aProgress, aProgressMax)

Called to notify the event sink that progress has occurred for the
given request.

Parameters

aRequest	the request being observed (may QI to nsIChannel).
aContext	if aRequest is a channel, then this parameter is the listener context passed to nsIChannel::asyncOpen.
aProgress	numeric value in the range 0 to aProgressMax indicating the number of bytes transfered thus far.
aProgressMax	numeric value indicating maximum number of bytes that will be transfered (or 0xFFFFFFFFFFFFFFFF if total is unknown).

onStatus(aRequest, aContext, aStatus, aStatusArg)

Called to notify the event sink with a status message for the given
request.

Parameters

aRequest	the request being observed (may QI to nsIChannel).
aContext	if aRequest is a channel, then this parameter is the listener context passed to nsIChannel::asyncOpen.
aStatus	status code (not necessarily an error code) indicating the state of the channel (usually the state of the underlying transport). see nsISocketTransport for socket specific status codes.
aStatusArg	status code argument to be used with the string bundle service to convert the status message into localized, human readable text. the meaning of this parameter is specific to the value of the status code. for socket status codes, this parameter indicates the host:port associated with the status code.