1 files changed, 80 insertions, 0 deletions
diff --git a/src/contrib/semaphore.c b/src/contrib/semaphore.c
new file mode 100644
index 0000000..ad50dcc
--- /dev/null
+++ b/src/contrib/semaphore.c
@@ -0,0 +1,80 @@
+/*  Copyright (C) 2019 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include "semaphore.h"
+
+#include <assert.h>
+#include <stdlib.h>
+
+#if defined(__APPLE__)
+#pragma clang diagnostic ignored "-Wdeprecated-declarations"
+#endif
+
+void knot_sem_init(knot_sem_t *sem, unsigned int value)
+{
+	int ret = sem_init(&sem->semaphore, 1, value);
+	if (ret == 0) {
+		sem->status = -1;
+	} else {
+		sem->status = value;
+		sem->status_lock = malloc(sizeof(*sem->status_lock));
+		pthread_mutex_init(&sem->status_lock->mutex, NULL);
+		pthread_cond_init(&sem->status_lock->cond, NULL);
+	}
+}
+
+void knot_sem_wait(knot_sem_t *sem)
+{
+	if (sem->status < 0) {
+		int semret;
+		do {
+			semret = sem_wait(&sem->semaphore);
+		} while (semret != 0); // repeat wait as it might be interrupted by a signal
+	} else {
+		pthread_mutex_lock(&sem->status_lock->mutex);
+		while (sem->status == 0) {
+			pthread_cond_wait(&sem->status_lock->cond, &sem->status_lock->mutex);
+		}
+		sem->status--;
+		pthread_mutex_unlock(&sem->status_lock->mutex);
+	}
+}
+
+void knot_sem_post(knot_sem_t *sem)
+{
+	if (sem->status < 0) {
+		int semret = sem_post(&sem->semaphore);
+		(void)semret;
+		assert(semret == 0);
+	} else {
+		pthread_mutex_lock(&sem->status_lock->mutex);
+		sem->status++;
+		pthread_cond_signal(&sem->status_lock->cond);
+		pthread_mutex_unlock(&sem->status_lock->mutex);
+	}
+}
+
+void knot_sem_destroy(knot_sem_t *sem)
+{
+	knot_sem_wait(sem);
+	if (sem->status < 0) {
+		sem_destroy(&sem->semaphore);
+	} else {
+		pthread_cond_destroy(&sem->status_lock->cond);
+		pthread_mutex_destroy(&sem->status_lock->mutex);
+		free(sem->status_lock);
+	}
+}