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+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+/*
+ * Copyright 2007 Sun Microsystems, Inc. All rights reserved.
+ * Use is subject to license terms.
+ */
+
+#ifndef _SYS_UNIQUE_H
+#define _SYS_UNIQUE_H
+
+#pragma ident "%Z%%M% %I% %E% SMI"
+
+#include <sys/zfs_context.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* The number of significant bits in each unique value. */
+#define UNIQUE_BITS 56
+
+void unique_init(void);
+void unique_fini(void);
+
+/*
+ * Return a new unique value (which will not be uniquified against until
+ * it is unique_insert()-ed.
+ */
+uint64_t unique_create(void);
+
+/* Return a unique value, which equals the one passed in if possible. */
+uint64_t unique_insert(uint64_t value);
+
+/* Indicate that this value no longer needs to be uniquified against. */
+void unique_remove(uint64_t value);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _SYS_UNIQUE_H */