1 | /* SPDX-License-Identifier: LGPL-2.1-or-later */ |
2 | /* |
3 | * Provides fixed-point logarithm operations. |
4 | * |
5 | * Copyright (C) 2006 Christoph Pfister (christophpfister@gmail.com) |
6 | */ |
7 | |
8 | #ifndef __LINUX_INT_LOG_H |
9 | #define __LINUX_INT_LOG_H |
10 | |
11 | #include <linux/types.h> |
12 | |
13 | /** |
14 | * intlog2 - computes log2 of a value; the result is shifted left by 24 bits |
15 | * |
16 | * @value: The value (must be != 0) |
17 | * |
18 | * to use rational values you can use the following method: |
19 | * |
20 | * intlog2(value) = intlog2(value * 2^x) - x * 2^24 |
21 | * |
22 | * Some usecase examples: |
23 | * |
24 | * intlog2(8) will give 3 << 24 = 3 * 2^24 |
25 | * |
26 | * intlog2(9) will give 3 << 24 + ... = 3.16... * 2^24 |
27 | * |
28 | * intlog2(1.5) = intlog2(3) - 2^24 = 0.584... * 2^24 |
29 | * |
30 | * |
31 | * return: log2(value) * 2^24 |
32 | */ |
33 | extern unsigned int intlog2(u32 value); |
34 | |
35 | /** |
36 | * intlog10 - computes log10 of a value; the result is shifted left by 24 bits |
37 | * |
38 | * @value: The value (must be != 0) |
39 | * |
40 | * to use rational values you can use the following method: |
41 | * |
42 | * intlog10(value) = intlog10(value * 10^x) - x * 2^24 |
43 | * |
44 | * An usecase example: |
45 | * |
46 | * intlog10(1000) will give 3 << 24 = 3 * 2^24 |
47 | * |
48 | * due to the implementation intlog10(1000) might be not exactly 3 * 2^24 |
49 | * |
50 | * look at intlog2 for similar examples |
51 | * |
52 | * return: log10(value) * 2^24 |
53 | */ |
54 | extern unsigned int intlog10(u32 value); |
55 | |
56 | #endif |
57 | |