1/* Copyright (c) 2013-2015 Jeffrey Pfau
 2 *
 3 * This Source Code Form is subject to the terms of the Mozilla Public
 4 * License, v. 2.0. If a copy of the MPL was not distributed with this
 5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 6#ifndef UTIL_MATH_H
 7#define UTIL_MATH_H
 8
 9#include <mgba-util/common.h>
10
11CXX_GUARD_START
12
13static inline uint32_t popcount32(unsigned bits) {
14	bits = bits - ((bits >> 1) & 0x55555555);
15	bits = (bits & 0x33333333) + ((bits >> 2) & 0x33333333);
16	return (((bits + (bits >> 4)) & 0xF0F0F0F) * 0x1010101) >> 24;
17}
18
19static inline unsigned clz32(uint32_t bits) {
20#if defined(__GNUC__) || __clang__
21	return __builtin_clz(bits);
22#else
23	static const int table[256] = {
24		8, 7, 6, 6, 5, 5, 5, 5, 4, 4, 4, 4, 4, 4, 4, 4,
25		3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
26		2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
27		2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
28		1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
29		1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
30		1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
31		1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
32		0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
33		0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
34		0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
35		0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
36		0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
37		0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
38		0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
39		0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
40	};
41
42	if (bits & 0xFF000000) {
43		return table[bits >> 24];
44	} else if (bits & 0x00FF0000) {
45		return table[bits >> 16] + 8;
46	} else if (bits & 0x0000FF00) {
47		return table[bits >> 8] + 16;
48	}
49	return table[bits] + 24;
50#endif
51}
52
53static inline uint32_t toPow2(uint32_t bits) {
54	if (!bits) {
55		return 0;
56	}
57	unsigned lz = clz32(bits - 1);
58	return 1 << (32 - lz);
59}
60
61CXX_GUARD_END
62
63#endif