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diff --git a/common-src/semaphore.h b/common-src/semaphore.h
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+/*
+ * Copyright (c) 2005 Zmanda, Inc.  All Rights Reserved.
+ * 
+ * This library is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License version 2.1 as 
+ * published by the Free Software Foundation.
+ * 
+ * This library 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 Lesser General Public
+ * License for more details.
+ * 
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library; 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 Mathlida Ave, Suite 300
+ * Sunnyvale, CA 94086, USA, or: http://www.zmanda.com
+ */
+
+/* GLib does not provide semaphores, which are useful in queue.c.
+   So, we implement it here. */
+
+#include <glib.h>
+
+#ifndef SEMAPHORE_H
+
+typedef struct {
+    int value;
+    GMutex *mutex;
+    GCond * decrement_cond;
+    GCond * zero_cond;
+} semaphore_t;
+
+/* Create a new semaphore object with the given value.
+ *
+ * @param value: new value
+ * @returns: newly allocated semaphore_t
+ */
+semaphore_t* semaphore_new_with_value(int value);
+
+/* Shortcut to make a new semaphore with value 1.
+ */
+#define semaphore_new() semaphore_new_with_value(1)
+
+/* Free a semaphore allocated by semaphore_with_new_value().  Be sure the
+ * semaphore is no longer in use by any threads.
+ *
+ * @param sem: the semaphore to free
+ */
+void semaphore_free(semaphore_t *sem);
+
+/* Increment the value of the semaphore by incr.  This corresponds to
+ * Dijkstra's V(), or the typical semaphore's release().
+ *
+ * This function will not block, but may wake other threads waiting
+ * on semaphore_decrement().
+ *
+ * @param sem: the semaphore
+ * @param incr: added to the semaphore's value
+ */
+void semaphore_increment(semaphore_t *sem, unsigned int incr);
+
+/* Shortcut to increment the semaphore by 1.
+ */
+#define semaphore_up(semaphore) semaphore_increment(semaphore,1)
+
+/* Decrement the value of the semaphore by incr.  If this operation
+ * would make the semaphore negative, block until the semaphore
+ * value is large enough, then perform the decerement operation. Threads
+ * waiting on semaphore_wait_empty() may be awakened if the value
+ * reaches 0.
+ *
+ * @param sem: the semaphore
+ * @param decr: subtracted from the semaphore's value
+ */
+void semaphore_decrement(semaphore_t *sem, unsigned int decr);
+
+/* Shortcut to decrement the semaphore by 1.
+ */
+#define semaphore_down(semaphore) semaphore_decrement(semaphore, 1)
+
+/* Increment or decrement (with a negative incr) the value without
+ * blocking.  Threads waiting on semaphore_decrement() or
+ * semaphore_wait_empty() will be awakened if necessary.
+ *
+ * @param sem: the semaphore
+ * @param incr: added to the semaphore's value
+ */
+void semaphore_force_adjust(semaphore_t *sem, int incr);
+
+/* Set the semaphore to a given value without blocking.  Threads
+ * waiting on semaphore_decrement() or semaphore_wait_empty()
+ * will be awakened if necessary.
+ *
+ * @param sem: the semaphore
+ * @param value: the new value
+ */
+void semaphore_force_set(semaphore_t *sem, int value);
+
+/* Block until the semaphore's value is zero.
+ *
+ * @param sem: the semaphore
+ */
+void semaphore_wait_empty(semaphore_t *sem);
+
+#endif /* SEMAPHORE_H */