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
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