Re: Single process output reading

[storm@cua.dk (Kim F. Storm)]

Milan Zamazal <pdm@brailcom.org> writes:

> I think a way to read an output of just a single asynchronous process in
> Emacs is needed.  I.e. a way to invoke accept-process-output without
> possible invocation of another process filter function or a timer.

Your reasons sound valid to me, but blocking everything including timers
isn't very good, but may be acceptable for very short periods of time.

> IMO a better way would be to allow restricting accept-process-output to
> just a single process output reading.  Then the speech output system,
> aware of possible consequences of advising 'message' etc., could invoke
> accept-process-output in the restricted form, without the danger of
> unwanted side effects.

Here's an (untested) patch that adds a "just-this-one" arg to
accept-process-output

To avoid running timers, specify an integer as fourth arg, e.g.
  (accept-process-output your-process nil nil 1)


*** process.c	29 Jul 2004 16:46:31 +0200	1.434
--- process.c	16 Aug 2004 16:25:16 +0200	
***************
*** 3718,3734 ****
  }
  \f
  DEFUN ("accept-process-output", Faccept_process_output, Saccept_process_output,
!        0, 3, 0,
         doc: /* Allow any pending output from subprocesses to be read by Emacs.
  It is read into the process' buffers or given to their filter functions.
  Non-nil arg PROCESS means do not return until some output has been received
  from PROCESS.
  Non-nil second arg TIMEOUT and third arg TIMEOUT-MSECS are number of
  seconds and microseconds to wait; return after that much time whether
  or not there is input.
  Return non-nil iff we received any output before the timeout expired.  */)
!      (process, timeout, timeout_msecs)
!      register Lisp_Object process, timeout, timeout_msecs;
  {
    int seconds;
    int useconds;
--- 3718,3737 ----
  }
  \f
  DEFUN ("accept-process-output", Faccept_process_output, Saccept_process_output,
!        0, 4, 0,
         doc: /* Allow any pending output from subprocesses to be read by Emacs.
  It is read into the process' buffers or given to their filter functions.
  Non-nil arg PROCESS means do not return until some output has been received
  from PROCESS.
+ If optional fourth arg JUST-THIS-ONE is non-nil, only accept output
+ from PROCESS, suspending reading output from other processes.
+ If JUST-THIS-ONE is an integer, don't run any timers either.
  Non-nil second arg TIMEOUT and third arg TIMEOUT-MSECS are number of
  seconds and microseconds to wait; return after that much time whether
  or not there is input.
  Return non-nil iff we received any output before the timeout expired.  */)
!      (process, timeout, timeout_msecs, just_this_one)
!      register Lisp_Object process, timeout, timeout_msecs, just_this_one;
  {
    int seconds;
    int useconds;
***************
*** 3776,3782 ****
      XSETFASTINT (process, 0);
  
    return
!     (wait_reading_process_input (seconds, useconds, process, 0)
       ? Qt : Qnil);
  }
  
--- 3779,3787 ----
      XSETFASTINT (process, 0);
  
    return
!     (wait_reading_process_input (seconds, useconds, process,
! 				 NILP (just_this_one) ? 0 :
! 				 !INTEGERP (just_this_one) ? -1 : -2)
       ? Qt : Qnil);
  }
  
***************
*** 4032,4037 ****
--- 4037,4043 ----
    EMACS_TIME timeout, end_time;
    int wait_channel = -1;
    struct Lisp_Process *wait_proc = 0;
+   int just_the_wait_proc = 0;
    int got_some_input = 0;
    /* Either nil or a cons cell, the car of which is of interest and
       may be changed outside of this routine.  */
***************
*** 4048,4053 ****
--- 4054,4064 ----
        wait_proc = XPROCESS (read_kbd);
        wait_channel = XINT (wait_proc->infd);
        XSETFASTINT (read_kbd, 0);
+       if (do_display < 0)
+ 	{
+ 	  just_the_wait_proc = do_display;
+ 	  do_display = 0;
+ 	}
      }
  
    /* If waiting for non-nil in a cell, record where.  */
***************
*** 4122,4128 ****
  	 But not if wait_for_cell; in those cases,
  	 the wait is supposed to be short,
  	 and those callers cannot handle running arbitrary Lisp code here.  */
!       if (NILP (wait_for_cell))
  	{
  	  EMACS_TIME timer_delay;
  
--- 4133,4140 ----
  	 But not if wait_for_cell; in those cases,
  	 the wait is supposed to be short,
  	 and those callers cannot handle running arbitrary Lisp code here.  */
!       if (NILP (wait_for_cell)
! 	  && just_the_wait_proc != -2)
  	{
  	  EMACS_TIME timer_delay;
  
***************
*** 4258,4264 ****
  
        /* Wait till there is something to do */
  
!       if (!NILP (wait_for_cell))
  	{
  	  Available = non_process_wait_mask;
  	  check_connect = check_delay = 0;
--- 4270,4281 ----
  
        /* Wait till there is something to do */
  
!       if (just_the_wait_proc)
! 	{
! 	  FD_SET (wait_channel, &Available);
! 	  check_connect = check_delay = 0;
! 	}
!       else if (!NILP (wait_for_cell))
  	{
  	  Available = non_process_wait_mask;
  	  check_connect = check_delay = 0;


--
Kim F. Storm <storm@cua.dk> http://www.cua.dk