conmon: Add polling_set_t epoll helper

This is a tiny helper that makes using epoll a bit less painful.

conmon/pollset.c

@@ -0,0 +1,103 @@
+#define _GNU_SOURCE
+
+#include <glib.h>
+#include <sys/epoll.h>
+#include <unistd.h>
+#include <errno.h>
+
+#include "pollset.h"
+
+#define MAX_EVENTS 10
+
+typedef struct _polling_fd_t polling_fd_t;
+struct _polling_fd_t {
+	int fd;
+	polling_set_input_cb input_cb;
+	polling_set_error_cb error_cb;
+	gpointer user_data;
+};
+
+static void polling_fd_free(polling_fd_t *polling_fd)
+{
+        if (polling_fd->fd >= 0)
+		close(polling_fd->fd);
+	g_free(polling_fd);
+}
+
+int polling_set_init(polling_set_t *set)
+{
+	set->epfd = epoll_create1(EPOLL_CLOEXEC);
+	if (set->epfd < 0)
+		return -1;
+	set->fd_hash = g_hash_table_new_full(g_direct_hash, g_direct_equal,
+					     NULL, (GDestroyNotify)polling_fd_free);
+	return 0;
+}
+
+void polling_set_destroy(polling_set_t *set)
+{
+	if (set->epfd >= 0)
+		close(set->epfd);
+	if (set->fd_hash)
+		g_hash_table_destroy(set->fd_hash);
+}
+
+int polling_set_add_fd(polling_set_t *set, int fd, polling_set_input_cb input_cb, polling_set_error_cb error_cb, gpointer user_data)
+{
+	struct epoll_event ev;
+	polling_fd_t *polling_fd;
+	
+	ev.events = EPOLLIN;
+	ev.data.fd = fd;
+
+	if (epoll_ctl(set->epfd, EPOLL_CTL_ADD, ev.data.fd, &ev) < 0)
+		return -1;
+
+	polling_fd = g_new0(polling_fd_t, 1);
+	polling_fd->fd = fd;
+	polling_fd->input_cb = input_cb;
+	polling_fd->error_cb = error_cb;
+	polling_fd->user_data = user_data;
+
+	g_hash_table_insert(set->fd_hash, GINT_TO_POINTER(fd), polling_fd);
+	return 0;
+}
+
+void polling_set_remove_fd(polling_set_t *set, int fd)
+{
+	g_hash_table_remove(set->fd_hash, GINT_TO_POINTER(fd));
+}
+
+int polling_set_iterate(polling_set_t *set)
+{
+	struct epoll_event evlist[MAX_EVENTS];
+	int ready;
+
+	do {
+		ready = epoll_wait(set->epfd, evlist, MAX_EVENTS, -1);
+	} while (ready == -1 && errno == EINTR);
+
+	if (ready < 0)
+		return -1;
+
+	for (int i = 0; i < ready; i++) {
+		int fd = evlist[i].data.fd;
+		polling_fd_t *polling_fd = g_hash_table_lookup(set->fd_hash, GINT_TO_POINTER(fd));
+
+		if (polling_fd == NULL)
+			continue;
+
+		if (evlist[i].events & EPOLLIN &&
+		    polling_fd->input_cb)
+			polling_fd->input_cb(set, fd, polling_fd->user_data);
+		else if (evlist[i].events & (EPOLLHUP | EPOLLERR)) {
+			bool remove = true;
+			if (polling_fd->error_cb)
+				remove = polling_fd->error_cb(set, fd, polling_fd->user_data);
+			if (remove)
+				polling_set_remove_fd(set, fd);
+		}
+  	}
+
+	return 0;
+}

conmon/pollset.h

@@ -0,0 +1,22 @@
+#pragma once
+
+#include <stdbool.h>
+
+typedef struct _polling_set_t polling_set_t;
+struct _polling_set_t {
+	int epfd;
+	GHashTable *fd_hash;
+};
+
+#define POLLING_SET_INIT { -1, NULL }
+
+typedef void (*polling_set_input_cb) (polling_set_t *set, int fd, gpointer user_data);
+typedef bool (*polling_set_error_cb) (polling_set_t *set, int fd, gpointer user_data);
+
+int polling_set_init(polling_set_t *set);
+void polling_set_destroy(polling_set_t *set);
+int polling_set_add_fd(polling_set_t *set, int fd, polling_set_input_cb input_cb, polling_set_error_cb error_cb, gpointer user_data);
+
+int polling_set_iterate(polling_set_t *set);
+
+#define _cleanup_pollset_ __attribute__((cleanup(polling_set_destroy)))