usr/src/common/util/ffs.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21
  22 /*
  23  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  */
  26
  27 #pragma ident   "%Z%%M% %I%     %E% SMI"
  28
  29 /*
  30  * Common implementation of ffs for kernel, mdb, and libc.  Note that mdb
  31  * renames ffs into mdb_ffs to avoid user-space clashes with the signature of
  32  * ffs(3C).
  33  */
  34
  35 #if defined(_KERNEL) || defined(ffs)
  36 #include <sys/int_types.h>
  37 #define arg_t   uintmax_t
  38 #else
  39 #define arg_t   int
  40 #include "lint.h"
  41 #endif
  42
  43 int
  44 ffs(arg_t bits)
  45 {
  46         int i;
  47
  48         if (bits == 0)
  49                 return (0);
  50         for (i = 1; ; i++, bits >>= 1) {
  51                 if (bits & 1)
  52                         break;
  53         }
  54         return (i);
  55 }