1 /* libFLAC - Free Lossless Audio Codec library
2 * Copyright (C) 2001,2002,2003,2004,2005,2006,2007 Josh Coalson
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 *
8 * - Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 *
11 * - Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 *
15 * - Neither the name of the Xiph.org Foundation nor the names of its
16 * contributors may be used to endorse or promote products derived from
17 * this software without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
21 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
22 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR
23 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
24 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
25 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
26 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
27 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
28 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
29 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
30 */
31
32 #if HAVE_CONFIG_H
33 # include <config.h>
34 #endif
35
36 #include "private/bitmath.h"
37 #include "FLAC/assert.h"
38
39 /* An example of what FLAC__bitmath_ilog2() computes:
40 *
41 * ilog2( 0) = assertion failure
42 * ilog2( 1) = 0
43 * ilog2( 2) = 1
44 * ilog2( 3) = 1
45 * ilog2( 4) = 2
46 * ilog2( 5) = 2
47 * ilog2( 6) = 2
48 * ilog2( 7) = 2
49 * ilog2( 8) = 3
50 * ilog2( 9) = 3
51 * ilog2(10) = 3
52 * ilog2(11) = 3
53 * ilog2(12) = 3
54 * ilog2(13) = 3
55 * ilog2(14) = 3
56 * ilog2(15) = 3
57 * ilog2(16) = 4
58 * ilog2(17) = 4
59 * ilog2(18) = 4
60 */
FLAC__bitmath_ilog2(FLAC__uint32 v)61 unsigned FLAC__bitmath_ilog2(FLAC__uint32 v)
62 {
63 unsigned l = 0;
64 FLAC__ASSERT(v > 0);
65 while(v >>= 1)
66 l++;
67 return l;
68 }
69
FLAC__bitmath_ilog2_wide(FLAC__uint64 v)70 unsigned FLAC__bitmath_ilog2_wide(FLAC__uint64 v)
71 {
72 unsigned l = 0;
73 FLAC__ASSERT(v > 0);
74 while(v >>= 1)
75 l++;
76 return l;
77 }
78
79 /* An example of what FLAC__bitmath_silog2() computes:
80 *
81 * silog2(-10) = 5
82 * silog2(- 9) = 5
83 * silog2(- 8) = 4
84 * silog2(- 7) = 4
85 * silog2(- 6) = 4
86 * silog2(- 5) = 4
87 * silog2(- 4) = 3
88 * silog2(- 3) = 3
89 * silog2(- 2) = 2
90 * silog2(- 1) = 2
91 * silog2( 0) = 0
92 * silog2( 1) = 2
93 * silog2( 2) = 3
94 * silog2( 3) = 3
95 * silog2( 4) = 4
96 * silog2( 5) = 4
97 * silog2( 6) = 4
98 * silog2( 7) = 4
99 * silog2( 8) = 5
100 * silog2( 9) = 5
101 * silog2( 10) = 5
102 */
FLAC__bitmath_silog2(int v)103 unsigned FLAC__bitmath_silog2(int v)
104 {
105 while(1) {
106 if(v == 0) {
107 return 0;
108 }
109 else if(v > 0) {
110 unsigned l = 0;
111 while(v) {
112 l++;
113 v >>= 1;
114 }
115 return l+1;
116 }
117 else if(v == -1) {
118 return 2;
119 }
120 else {
121 v++;
122 v = -v;
123 }
124 }
125 }
126
FLAC__bitmath_silog2_wide(FLAC__int64 v)127 unsigned FLAC__bitmath_silog2_wide(FLAC__int64 v)
128 {
129 while(1) {
130 if(v == 0) {
131 return 0;
132 }
133 else if(v > 0) {
134 unsigned l = 0;
135 while(v) {
136 l++;
137 v >>= 1;
138 }
139 return l+1;
140 }
141 else if(v == -1) {
142 return 2;
143 }
144 else {
145 v++;
146 v = -v;
147 }
148 }
149 }
150