Re: sending data to an asynchronous process

[Jean Louis <bugs@gnu.support>]

* Nicolas Graner <nicolas@graner.name> [2021-04-02 21:37]:
> Jean Louis <bugs@gnu.support> wrote on 2021-04-02 20:18:
> > * Nicolas Graner <nicolas@graner.name> [2021-04-02 13:21]:
> >> I am writing a program that creates audio samples in an emacs
> >> buffer, then sends them to an external program (sox) to play in
> >> the background while I continue working with emacs. Part of the
> >> code is roughly as follows:
> >> 
> > (setq process
> >       (let ((process-connection-type nil))
> > 	(start-process "my-process" nil
> > 		       "sox" "-r" rate "-c" channels "-b" bits "-e" encoding "-q" "-d")))
> > (process-send-region process start end)
> > (process-send-eof process)
> >
> > For process-send-region, it says:
> >
> > If PROCESS is a non-blocking network process that hasn’t been fully
> > set up yet, this function will block until socket setup has completed.
> >
> > Maybe that applies.

(defun rcd-command-output-from-input (program input &rest args)
  "Returns output from PROGRAM INPUT with optional ARGS"
  (let* ((output (with-temp-buffer
		  (insert input)
		  (apply #'call-process-region nil nil program t t nil args)
		  (buffer-string))))
    output))

(rcd-command-output-from-input "sox" (buffer-string)
			       "-r" "44100"
			       "-c" "2"
			       "-b" "32"
			       "-e" "signed-integer"
			       "-t" "raw"
			       "-"
			       "-q"
			       "-d") → ""

I have tried this above, it plays my buffer. But it is not
asynchronous.

There is library async.el, but I am not sure if it can receive from
buffer directly, you can however, make your function to feed the
buffer first into a file.

async-start-process is an autoloaded compiled Lisp function in
‘async.el’.

(async-start-process NAME PROGRAM FINISH-FUNC &rest PROGRAM-ARGS)

Start the executable PROGRAM asynchronously named NAME.  See ‘async-start’.
PROGRAM is passed PROGRAM-ARGS, calling FINISH-FUNC with the
process object when done.  If FINISH-FUNC is nil, the future
object will return the process object when the program is
finished.  Set DEFAULT-DIRECTORY to change PROGRAM’s current
working directory.

async-send is a compiled Lisp function in ‘async.el’.

(async-send &rest ARGS)

Send the given messages to the asychronous Emacs PROCESS.


-- 
Jean

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