1 files changed, 82 insertions, 0 deletions
diff --git a/src/contrib/semaphore.h b/src/contrib/semaphore.h
new file mode 100644
index 0000000..5eadecf
--- /dev/null
+++ b/src/contrib/semaphore.h
@@ -0,0 +1,82 @@
+/*  Copyright (C) 2022 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/>.
+ */
+
+#pragma once
+
+#include <pthread.h>
+#include <semaphore.h>
+
+typedef struct {
+	pthread_mutex_t mutex;
+	pthread_cond_t cond;
+} knot_sem_nonposix_t;
+
+typedef struct {
+	int status;
+	union {
+		sem_t semaphore;
+		knot_sem_nonposix_t *status_lock;
+	};
+} knot_sem_t;
+
+/*!
+ * \brief Initialize semaphore by using POSIX sem_t if possible, custom value/mutex/cond structure otherwise.
+ */
+void knot_sem_init(knot_sem_t *sem, int value);
+
+/*!
+ * \brief Initialize semaphore, force using nonposix variant.
+ */
+void knot_sem_init_nonposix(knot_sem_t *sem, int value);
+
+/*!
+ * \brief Set semaphore value to specified value.
+ * \note This can be only used with nonposix semaphore.
+ */
+void knot_sem_reset(knot_sem_t *sem, int value);
+
+/*!
+ * \brief Lock the semaphore (decrement), block until it's non-negative.
+ */
+void knot_sem_wait(knot_sem_t *sem);
+
+/*!
+ * \brief Block until the semaphore could decrement, but keep the value unchanged.
+ * \note This can be only used with nonposix semaphore.
+ */
+void knot_sem_wait_post(knot_sem_t *sem);
+
+/*!
+ * \brief Force-lock the semaphore without blocking, it might get negative.
+ * \note This can be only used with nonposix semaphore.
+ */
+void knot_sem_get_ahead(knot_sem_t *sem);
+
+/*!
+ * \brief Lock the semaphore, abort() if it would block.
+ * \note This can be only used with nonposix semaphore.
+ */
+void knot_sem_get_assert(knot_sem_t *sem);
+
+/*!
+ * \brief Unlock the semaphore (increment).
+ */
+void knot_sem_post(knot_sem_t *sem);
+
+/*!
+ * \brief Uninitialize the semaphore. Calls knot_sem_wait once at the beginning.
+ */
+void knot_sem_destroy(knot_sem_t *sem);