examples

commit b6d66746d2680e1cc60a4eef54ba86ed559b8f37
parent eab5b7383124afd2f84ee52cb53b4324730a3266
Author: Henry Wilson <henry@henryandlizzy.uk>
Date:   Sat,  6 Aug 2022 00:21:49 +0100

epoll: Add timerfd example

Diffstat:
A
src/timerfd.c
 | 
82
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

1 file changed, 82 insertions(+), 0 deletions(-)
diff --git a/src/timerfd.c b/src/timerfd.c
@@ -0,0 +1,82 @@
+#include <sys/epoll.h>
+#include <sys/timerfd.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <ctype.h>
+
+static int timer, event_queue;
+
+static void succeed_or_die(int n, char const* msg)
+{
+	if (n >= 0)
+		return;
+
+	perror(msg);
+	exit(1);
+}
+
+static void stdin_event(void)
+{
+	char buf[64];
+	int n = read(STDIN_FILENO, buf, sizeof buf - 1);
+
+	if (n <= 0)
+	{
+		puts("Stdin closed.");
+		exit(0);
+	}
+	for (int i = 0; i < n; ++i)
+		if (iscntrl(buf[i]))
+			buf[i] = '.';
+	buf[n] = '\0';
+
+	printf("Stdin: '%s'\n", buf);
+}
+
+static void timerfd_event(void)
+{
+	static uint64_t ticks;
+	uint64_t new_ticks;
+	read(timer, &new_ticks, sizeof new_ticks);
+	ticks += new_ticks;
+	printf("Tick +%lu %lu\n", new_ticks, ticks);
+}
+
+int main()
+{
+	timer = timerfd_create(CLOCK_MONOTONIC, 0);
+	succeed_or_die(timer, "timerfd_create");
+
+	int res = timerfd_settime(timer, 0, &(struct itimerspec){
+               .it_interval = {1, 0},  /* Interval for periodic timer */
+               .it_value = {1, 0},     /* Initial expiration */
+        }, NULL);
+	succeed_or_die(res, "timerfd_settime");
+
+	event_queue = epoll_create1(0);
+	succeed_or_die(event_queue, "epoll_create2");
+
+	res = epoll_ctl(event_queue, EPOLL_CTL_ADD, STDIN_FILENO, &(struct epoll_event){
+               .events = EPOLLIN,
+               .data.ptr = stdin_event,
+        });
+	succeed_or_die(res, "epoll_ctl");
+
+	res = epoll_ctl(event_queue, EPOLL_CTL_ADD, timer, &(struct epoll_event){
+               .events = EPOLLIN,
+               .data.ptr = timerfd_event,
+        });
+	succeed_or_die(res, "epoll_ctl");
+
+	for (;;)
+	{
+		struct epoll_event events[8];
+		int n_events = epoll_wait(event_queue, events, sizeof events / sizeof *events, -1);
+		succeed_or_die(n_events, "epoll_wait");
+
+		for (int i = 0; i < n_events; ++i)
+			((void(*)(void))events[i].data.ptr)();
+	}
+}