Re: Synchronous signal delivery..

[Werner Almesberger]

I wrote:
>     ssize_t overwrite(int fd,
>       const void *data_if_empty,size_t size_if_empty,
>       const void *data_if_full,size_t size_if_full,
>       int *was_empty);

Bah, rubbish. Make this

    ssize_t overwrite(int fd,const void *data,size_t size);

If the pipe/queue is empty, don't write, and return 0. Now, this
could probably be implemented with a flag to send(2) (then this
wouldn't work for pipes, but you could use socketpair(2) for a
similar effect). Example:

void add_signal(int signum)
{
	static int signal_set = 0;
	int new_signal = 1 << signum;
	int sent;

	signal_set |= new_signal;
	sent = send(fd,&signal_set,sizeof(int),MSG_OVERWRITE);
	if (!sent) {
		send(fd,&new_signal,sizeof(int),0);
		signal_set = new_signal;
	}
}

- Werner

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  _________________________________________________________________________
 / Werner Almesberger, Buenos Aires, Argentina         [e-mail] /
/_http://www.almesberger.net/____________________________________________/