xref: /titanic_44/usr/src/lib/libc/port/gen/fls.c (revision a60349c89adffc0902b2353230891d8e7f2b24d9)
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 fls_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 >> 32)) != 0)
41 		i += 32;
42 	else
43 		bits32 = (uint32_t)bits;
44 
45 	if ((bits32 & 0xffff0000) != 0) {
46 		bits32 >>= 16;
47 		i += 16;
48 	}
49 	if ((bits32 & 0xff00) != 0) {
50 		bits32 >>= 8;
51 		i += 8;
52 	}
53 	if ((bits32 & 0xf0) != 0) {
54 		bits32 >>= 4;
55 		i += 4;
56 	}
57 	if ((bits32 & 0xc) != 0) {
58 		bits32 >>= 2;
59 		i += 2;
60 	}
61 	if ((bits32 & 0x2) != 0)
62 		i += 1;
63 
64 	return (i);
65 }
66 
67 int
68 fls(int bits)
69 {
70 	return (fls_impl((uint64_t)(uint_t)bits));
71 }
72 
73 int
74 flsl(long bits)
75 {
76 	return (fls_impl((uint64_t)(ulong_t)bits));
77 }
78 
79 int
80 flsll(long long bits)
81 {
82 	return (fls_impl((uint64_t)(u_longlong_t)bits));
83 }
84