Initial import.

The driver for now only prints the argument list and then fails.

1 files changed, 107 insertions, 0 deletions

diff --git a/semaphore.c b/semaphore.c
new file mode 100644
index 0000000..1f43652
--- /dev/null
+++ b/semaphore.c
@@ -0,0 +1,107 @@
+/* Authors: Martin Nagy <mnagy@redhat.com>
+ *
+ * Copyright (C) 2008  Red Hat
+ * see file 'COPYING' for use and warranty information
+ *
+ * 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; version 2 only
+ *
+ * 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, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+/*
+ * Note: This implementation doesn't prevent from starvation. This means that
+ * if a thread signals the semaphore and then waits for it, it may catch it's
+ * own signal. However, for our purposes, this shouldn't be needed.
+ */
+
+#include <isc/condition.h>
+#include <isc/result.h>
+#include <isc/util.h>
+
+#include "semaphore.h"
+
+/*
+ * Initialize a semaphore.
+ *
+ * sem - allocated semaphore that will be initialized
+ * value - number of times we can acquire the semaphore.
+ */
+isc_result_t
+semaphore_init(semaphore_t *sem, int value)
+{
+	isc_result_t result;
+
+	REQUIRE(sem != NULL);
+	REQUIRE(value > 0);
+
+	sem->value = value;
+	result = isc_mutex_init(&sem->mutex);
+	if (result != ISC_R_SUCCESS)
+		return result;
+
+	result = isc_condition_init(&sem->cond);
+	if (result != ISC_R_SUCCESS)
+		isc_mutex_destroy(&sem->mutex);
+
+	return result;
+}
+
+/*
+ * Destroy a semaphore.
+ *
+ * sem - semaphore to be destroyed.
+ */
+void
+semaphore_destroy(semaphore_t *sem)
+{
+	REQUIRE(sem != NULL);
+
+	REQUIRE(isc_mutex_destroy(&sem->mutex) == ISC_R_SUCCESS);
+	REQUIRE(isc_condition_destroy(&sem->cond) == ISC_R_SUCCESS);
+}
+
+/*
+ * Wait on semaphore. This operation will try to acquire a lock on the
+ * semaphore. If the semaphore is already acquired as many times at it allows,
+ * the function will block until someone releases the lock.
+ */
+void
+semaphore_wait(semaphore_t *sem)
+{
+	REQUIRE(sem != NULL);
+
+	LOCK(&sem->mutex);
+
+	sem->value--;
+	if (sem->value < 0)
+		WAIT(&sem->cond, &sem->mutex);
+
+	UNLOCK(&sem->mutex);
+}
+
+/*
+ * Release the semaphore. This will make sure that another thread (probably
+ * already waiting) will be able to acquire the semaphore.
+ */
+void
+semaphore_signal(semaphore_t *sem)
+{
+	REQUIRE(sem != NULL);
+
+	LOCK(&sem->mutex);
+
+	sem->value++;
+	if (sem->value >= 0)
+		SIGNAL(&sem->cond);
+
+	UNLOCK(&sem->mutex);
+}