| Allegro CL version 8.2 Minimal update since 8.2 release. 8.1 version |
Arguments: stream-or-fds &key wait-function whostate timeout
This lower-level function extends the capabilities of mp:process-wait and mp:process-wait-with-timeout to allow a process to wait for input from multiple streams and to wait for input from a file.
The stream-or-fds argument may be a single element or a list of elements. Each element may be a stream object or a file descriptor obtained from the operating system (typically a small non-negative integer).
This function waits for input to become available on any of the streams, and when that happens a list of streams/fds (some subset of the given stream-or-fds argument) that have input available is returned. Here have input available means (when the default wait-function is used) that a subsequent call to read-char or read-byte will immediately return without blocking. (It might return end-of-file status, however).
The wait-function argument should be a
function that accepts one argument. If a single stream-or-fd is passed
as the stream-or-fds argument, then the wait
function will be called with that stream-or-fd. If a list of
stream-or-fds is supplied to wait-for-input-available then the wait function
will be called on each of those stream-or-fds in turn until it returns
non-nil
. If every one of the stream-or-fds
gets us a nil
return on the first pass, then
this process goes into a wait, with enough information handy to let us
do an appropriate select-equivalent OS call when there are no
processes ready to run.
The default value for the wait-function
keyword argument is #'stream-listen
. This generic function
has methods defined both for integer file descriptors and for
terminal, socket, or other "interactive'' streams. This function
may be applied to streams that do not have a corresponding file
descriptor, such as a window-stream (in Common Windows on Unix).
If you supply your own wait-function, it must determine whether input is available for there is no additional test made by wait-for-input-available beyond the value returned by the wait function.
While waiting, the current process's whostate is set to the value
specified for the whostate keyword argument, defaulting to
"waiting for input", as if a
process-wait or
process-wait-with-timeout
were being called. If a value is specified for the timeout
keyword argument and no stream has input available before the timeout
occurs, nil
is returned. The value of the
timeout argument (if it is specified) should be a
non-negative real number. The units are seconds. Note that a value
less than the granularity of the system will timeout immediately.
See the discussion in the following sections in multiprocessing.htm for information on why to use this function rather than process-wait when waiting for input from a file. Note that the :os-threads and non :os-threads versions are discussed in different sections.
See also process-wait and waiting-for-input-available.
See multiprocessing.htm for general information on multiprocessing in Allegro CL.
Copyright (c) 1998-2016, Franz Inc. Oakland, CA., USA. All rights reserved.
This page was not revised from the 8.1 page.
Created 2010.1.21.
| Allegro CL version 8.2 Minimal update since 8.2 release. 8.1 version |