[Rd] Could Rstd_Busy do something (src/unix/sys-std.c)?

[Jakson Alves de Aquino]

On Sat, Dec 15, 2012 at 5:41 PM, Simon Urbanek
<simon.urbanek at r-project.org> wrote:
>
> On Dec 15, 2012, at 2:20 PM, Jakson Alves de Aquino wrote:
>
>> On Sat, Dec 15, 2012 at 1:09 PM, Simon Urbanek
>> <simon.urbanek at r-project.org> wrote:
>>> On Dec 15, 2012, at 6:36 AM, Jakson Alves de Aquino wrote:
>>>> I could avoid the crash if I knew that R is busy at the moment that
>>>> it receives the SIGWINCH. Thus my question is: Could Rstd_Busy()
>>>> set the value of a variable so packages like setwidth could know
>>>> that R is busy?
>>>
>>> You're looking at the wrong spot - the Busy callback is meant for UI
>>> signaling that R may enter a longer time of processing, it is not
>>> really an indicator that R is busy - R can be busy even without the
>>> busy state being signaled.
[...]
>>> The other way is to register an input handler and signal your FD
>>> when you get SIGWINCH, that guarantees that your handler will be
>>> called as soon as possible after the signal has arrived - that is
>>> probably what you want (see CarbonEL for a simple example how this
>>> is used).
>>
>> Based on CarbolEL, I added the following to setwidth_Start() function:
>>
>>    int fds[2];
>>    if(pipe(fds))
>>        Rprintf("pipe > 0\n");
>>    else
>>        Rprintf("pipe = 0\n");
>>    ifd = fds[0];
>>    ofd = fds[1];
>>    addInputHandler(R_InputHandlers, ifd, &uih, 32);
>>
>> And, also based on CarbolEL, I created the following uih() function:
>>
>>    static void uih(void *data) {
>>      char buf[16];
>>
>>      if(read(ifd, buf, 16) == 0){
>>          Rprintf("read = 0 :: %s\n", buf);
>>          Rprintf("%d written\n", write(ofd, buf, 16));
>>      } else {
>>          Rprintf("read != 0\n");
>>      }
>>    }
>>
>> However, the uih() function never gets called.
>>
>
> You didn't provide the signal yet - you have the initialization and
> receiving end ready - now you need to write the piece that triggers
> the input.

It works like a charm now. If handle_winch() is called a hundred times
while R is busy, uih() will also be called a hundred times, but only
when R is no longer busy:

    void handle_winch(int sig){
        signal(SIGWINCH, SIG_IGN);
        char buf[16];
        *buf = 0;
        if(write(ofd, buf, 16) <= 0)
            REprintf("setwidth error: write <= 0\n");
        signal(SIGWINCH, handle_winch);
    }

    static void uih(void *data) {
      char buf[16];
      if(read(ifd, buf, 16) == 0)
          REprintf("setwidth error: read = 0\n");
      R_ToplevelExec(setwidth_Set, NULL);
    }

I added the if(read()) and if(write()) to avoid compiler warnings
about return values not being used.

Thank you very much!

-- 
Jakson Alves de Aquino
Federal University of Ceará
Social Sciences Department
www.lepem.ufc.br/aquino.php