write-no-hang-p

Arguments: stream

If the argument stream is an integer, write-no-hang-p views that integer as an output file-descriptor, and it just checks the file-descriptor for readiness.

When stream is a stream, the output-handle of stream is queried to see if writing can be done. true is returned if writing can be done, else nil is returned. If the handle is itself a stream (an encapsulation), the stream is examined for output availability. If an error would be signalled on the stream, then true is returned, as if writing can be done.

In more detail, regardless of the type of stream, the buffer is checked for fullness. If it is not full, then true is returned.

If the buffer is full, then device-write is called with nil as the buffer, 0 as both start and end arguments, and blocking set to nil. If these return an indication that a write is possible, then true is returned, otherwise nil is returned.

See streams.htm for information on the simple-streams implementation in Allegro CL.

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This page was not revised from the 10.0 page.
Created 2019.8.20.