Merge branch 'master' into squeeze

[debian/amanda] / common-src / amsemaphore.c

diff --git a/common-src/amsemaphore.c b/common-src/amsemaphore.c
new file mode 100644 (file)
index 0000000..554e758
--- /dev/null
+++ b/common-src/amsemaphore.c
@@ -0,0 +1,122 @@
+/*
+ * Copyright (c) 2008, 2009, 2010 Zmanda, Inc.  All Rights Reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published
+ * by the Free Software Foundation.
+ *
+ * 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
+ *
+ * Contact information: Zmanda Inc., 465 S. Mathilda Ave., Suite 300
+ * Sunnyvale, CA 94085, USA, or: http://www.zmanda.com
+ */
+
+/* GLib does not provide semaphores, which are useful in queue.c.
+   So, we implement it here. */
+
+#include "amanda.h"
+#include "amsemaphore.h"
+
+amsemaphore_t* amsemaphore_new_with_value(int value) {
+    amsemaphore_t *rval;
+
+    if (!g_thread_supported())
+        return NULL;
+
+    rval = malloc(sizeof(*rval));
+    rval->value = value;
+    rval->mutex = g_mutex_new();
+    rval->decrement_cond = g_cond_new();
+    rval->zero_cond = g_cond_new();
+    
+    if (rval->mutex == NULL || rval->decrement_cond == NULL ||
+        rval->zero_cond == NULL) {
+        amsemaphore_free(rval);
+        return NULL;
+    } else {
+        return rval;
+    }
+}
+
+void amsemaphore_free(amsemaphore_t* o) {
+    g_mutex_free(o->mutex);
+    g_cond_free(o->decrement_cond);
+    g_cond_free(o->zero_cond);
+    free(o);
+}
+
+/* This function checks if the semaphore would is zero or negative.
+ * If so, the zero_cond is signalled. We assume that the mutex is
+ * locked. */
+static void check_empty(amsemaphore_t * o) {
+    if (o->value <= 0) {
+        g_cond_broadcast(o->zero_cond);
+    }
+}
+
+void amsemaphore_increment(amsemaphore_t* o, unsigned int inc) {
+    g_return_if_fail(o != NULL);
+    g_return_if_fail(inc != 0);
+
+    amsemaphore_force_adjust(o, inc);
+}
+
+void amsemaphore_decrement(amsemaphore_t* o, unsigned int dec) {
+    int sdec;
+    g_return_if_fail(o != NULL);
+    sdec = (int) dec;
+    g_return_if_fail(sdec >= 0);
+
+    g_mutex_lock(o->mutex);
+    while (o->value < sdec) {
+        g_cond_wait(o->decrement_cond, o->mutex);
+    }
+    o->value -= sdec;
+    check_empty(o);
+    g_mutex_unlock(o->mutex);
+}
+
+void amsemaphore_force_adjust(amsemaphore_t* o, int inc) {
+    g_return_if_fail(o != NULL);
+
+    g_mutex_lock(o->mutex);
+    o->value += inc;
+    if (inc < 0)
+       check_empty(o);
+    else
+       g_cond_broadcast(o->decrement_cond);
+    g_mutex_unlock(o->mutex);
+
+}
+
+void amsemaphore_force_set(amsemaphore_t* o, int value) {
+    int oldvalue;
+    g_return_if_fail(o != NULL);
+    
+    g_mutex_lock(o->mutex);
+    oldvalue = o->value;
+    o->value = value;
+    if (value < oldvalue)
+       check_empty(o);
+    else
+       g_cond_broadcast(o->decrement_cond);
+    g_mutex_unlock(o->mutex);
+    
+}
+
+void amsemaphore_wait_empty(amsemaphore_t * o) {
+    g_return_if_fail(o != NULL);
+    
+    g_mutex_lock(o->mutex);
+    while (o->value > 0) {
+        g_cond_wait(o->zero_cond, o->mutex);
+    }
+    g_mutex_unlock(o->mutex);
+}