integrate libreadline into a czmq event loop

zreadline.c

// example for integrating readline and
// synchronous signal delivery with czmq/zloop
// Michael Haberler 3/2014
// gcc -g zreadline.o `pkg-config --cflags --libs libczmq` -lreadline -o zreadline

#include <stdio.h>
#include <readline/readline.h>
#include <readline/history.h>
#include <stdlib.h>
#include <unistd.h>
#include <czmq.h>
#include <sys/signalfd.h>

int signo;
int eofseen = 0;
const char *prompt = "cmd> ";

static void my_rlhandler(char* line)
{
    if (line == NULL) {
	printf("EOF\n");
	eofseen = 1;
    } else {
	if (strlen(line)) {
	    add_history(line);
	}
	printf("got line: '%s'\n", line);
	free(line);
    }
}

static int s_handle_input(zloop_t *loop, zmq_pollitem_t *poller, void *arg)
{
    if (poller->revents & ZMQ_POLLIN)
	rl_callback_read_char();
    return 0;
}

static int s_handle_signal(zloop_t *loop, zmq_pollitem_t *poller, void *arg)
{
    struct signalfd_siginfo fdsi;
    ssize_t s = read(poller->fd, &fdsi, sizeof(struct signalfd_siginfo));
    if (s != sizeof(struct signalfd_siginfo)) {
	perror("read");
    }
    fprintf(stderr, "got signal %d '%s'\n",fdsi.ssi_signo,strsignal(fdsi.ssi_signo) );
    signo = fdsi.ssi_signo;
    return -1; // exit reactor
}

int main(int argc, char **argv)
{
    int sfd, retval;
    void *ctx  = zctx_new();
    assert(ctx);

    zloop_t *loop = zloop_new();
    assert (loop);

    // suppress default handling of signals in zctx_new()
    // since we're using signalfd()
    zsys_handler_set(NULL);

    sigset_t sigmask;
    sigemptyset(&sigmask);

    // block all signal delivery through default signal handlers
    // since we're using signalfd()
    sigfillset(&sigmask);
    assert(sigprocmask(SIG_SETMASK, &sigmask, NULL) == 0);

    // explicitly enable signals we want delivered via signalfd()
    sigemptyset(&sigmask);
    sigaddset(&sigmask, SIGINT);
    sigaddset(&sigmask, SIGQUIT);
    sigaddset(&sigmask, SIGTERM);
    sigaddset(&sigmask, SIGSEGV);
    sigaddset(&sigmask, SIGFPE);
    assert((sfd = signalfd(-1, &sigmask, 0)) >= 0);

    zmq_pollitem_t signal_poller =  { 0, sfd,   ZMQ_POLLIN };
    zloop_poller (loop, &signal_poller, s_handle_signal, NULL);

    // readline setup
    rl_callback_handler_install(prompt, (rl_vcpfunc_t*) &my_rlhandler);
    zmq_pollitem_t input_poller =  { 0, fileno(stdin),   ZMQ_POLLIN };
    zloop_poller (loop, &input_poller, s_handle_input, NULL);

    do {
	retval = zloop_start(loop);
    } while (!retval && !eofseen);

    rl_callback_handler_remove();
    fprintf(stderr, "exiting, signal %d, retval %d, eofseen %d\n",
	    signo, retval, eofseen);
    exit(0);
}