usr/src/lib/libc/port/gen/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 (c) 2010, Oracle and/or its affiliates. All rights reserved.
  24  */
  25
  26 #include "lint.h"
  27 #include <string.h>
  28 #include <strings.h>
  29 #include <sys/types.h>
  30
  31 static int
  32 ffs_impl(uint64_t bits)
  33 {
  34         int i = 1;
  35         uint32_t bits32;
  36
  37         if (bits == 0)
  38                 return (0);
  39
  40         if ((bits32 = (uint32_t)bits) == 0) {
  41                 bits32 = (uint32_t)(bits >> 32);
  42                 i += 32;
  43         }
  44
  45         if ((bits32 & 0xffff) == 0) {
  46                 bits32 >>= 16;
  47                 i += 16;
  48         }
  49         if ((bits32 & 0xff) == 0) {
  50                 bits32 >>= 8;
  51                 i += 8;
  52         }
  53         if ((bits32 & 0xf) == 0) {
  54                 bits32 >>= 4;
  55                 i += 4;
  56         }
  57         if ((bits32 & 0x3) == 0) {
  58                 bits32 >>= 2;
  59                 i += 2;
  60         }
  61         if ((bits32 & 0x1) == 0)
  62                 i += 1;
  63
  64         return (i);
  65 }
  66
  67 int
  68 ffs(int bits)
  69 {
  70         return (ffs_impl((uint64_t)(uint_t)bits));
  71 }
  72
  73 int
  74 ffsl(long bits)
  75 {
  76         return (ffs_impl((uint64_t)(ulong_t)bits));
  77 }
  78
  79 int
  80 ffsll(long long bits)
  81 {
  82         return (ffs_impl((uint64_t)(u_longlong_t)bits));
  83 }