Copied the benaphore implementation from the kernel for use in libroot.

Would be nice to actually share those.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@24748 a95241bf-73f2-0310-859d-f6bbb57e9c96

headers/private/libroot/libroot_lock.h

@@ -0,0 +1,82 @@
+/*
+ * Copyright 2002-2008, Axel Dörfler, axeld@pinc-software.de.
+ * Distributed under the terms of the MIT License.
+ *
+ * Copyright 2001-2002, Travis Geiselbrecht. All rights reserved.
+ * Distributed under the terms of the NewOS License.
+ */
+#ifndef _LIBROOT_LOCK_H
+#define _LIBROOT_LOCK_H
+
+#include <OS.h>
+
+
+// TODO: Copied from the kernel private lock.h/lock.c. We should somehow make
+// that code reusable.
+
+
+namespace BPrivate {
+
+
+typedef struct benaphore {
+	sem_id	sem;
+	int32	count;
+} benaphore;
+
+
+static inline status_t
+benaphore_init(benaphore *ben, const char *name)
+{
+	if (ben == NULL || name == NULL)
+		return B_BAD_VALUE;
+
+	ben->count = 1;
+	ben->sem = create_sem(0, name);
+	if (ben->sem >= B_OK)
+		return B_OK;
+
+	return ben->sem;
+}
+
+
+static inline status_t
+benaphore_lock_etc(benaphore *ben, uint32 flags, bigtime_t timeout)
+{
+	if (atomic_add(&ben->count, -1) <= 0)
+		return acquire_sem_etc(ben->sem, 1, flags, timeout);
+
+	return B_OK;
+}
+
+
+static inline status_t
+benaphore_lock(benaphore *ben)
+{
+	if (atomic_add(&ben->count, -1) <= 0)
+		return acquire_sem(ben->sem);
+
+	return B_OK;
+}
+
+
+static inline status_t
+benaphore_unlock(benaphore *ben)
+{
+	if (atomic_add(&ben->count, 1) < 0)
+		return release_sem(ben->sem);
+
+	return B_OK;
+}
+
+
+}	// namespace BPrivate
+
+
+using BPrivate::benaphore;
+using BPrivate::benaphore_init;
+using BPrivate::benaphore_lock_etc;
+using BPrivate::benaphore_lock;
+using BPrivate::benaphore_unlock;
+
+
+#endif	// _LIBROOT_LOCK_H