1 /* SPDX-License-Identifier: GPL-2.0-or-later */ 2 #ifndef _FIXP_ARITH_H 3 #define _FIXP_ARITH_H 4 5 #include <linux/bug.h> 6 #include <linux/math64.h> 7 8 /* 9 * Simplistic fixed-point arithmetics. 10 * Hmm, I'm probably duplicating some code :( 11 * 12 * Copyright (c) 2002 Johann Deneux 13 */ 14 15 /* 16 * 17 * Should you need to contact me, the author, you can do so by 18 * e-mail - mail your message to <johann.deneux@gmail.com> 19 */ 20 21 #include <linux/types.h> 22 23 static const s32 sin_table[] = { 24 0x00000000, 0x023be165, 0x04779632, 0x06b2f1d2, 0x08edc7b6, 0x0b27eb5c, 25 0x0d61304d, 0x0f996a26, 0x11d06c96, 0x14060b67, 0x163a1a7d, 0x186c6ddd, 26 0x1a9cd9ac, 0x1ccb3236, 0x1ef74bf2, 0x2120fb82, 0x234815ba, 0x256c6f9e, 27 0x278dde6e, 0x29ac379f, 0x2bc750e8, 0x2ddf003f, 0x2ff31bdd, 0x32037a44, 28 0x340ff241, 0x36185aee, 0x381c8bb5, 0x3a1c5c56, 0x3c17a4e7, 0x3e0e3ddb, 29 0x3fffffff, 0x41ecc483, 0x43d464fa, 0x45b6bb5d, 0x4793a20f, 0x496af3e1, 30 0x4b3c8c11, 0x4d084650, 0x4ecdfec6, 0x508d9210, 0x5246dd48, 0x53f9be04, 31 0x55a6125a, 0x574bb8e5, 0x58ea90c2, 0x5a827999, 0x5c135399, 0x5d9cff82, 32 0x5f1f5ea0, 0x609a52d1, 0x620dbe8a, 0x637984d3, 0x64dd894f, 0x6639b039, 33 0x678dde6d, 0x68d9f963, 0x6a1de735, 0x6b598ea1, 0x6c8cd70a, 0x6db7a879, 34 0x6ed9eba0, 0x6ff389de, 0x71046d3c, 0x720c8074, 0x730baeec, 0x7401e4bf, 35 0x74ef0ebb, 0x75d31a5f, 0x76adf5e5, 0x777f903b, 0x7847d908, 0x7906c0af, 36 0x79bc384c, 0x7a6831b8, 0x7b0a9f8c, 0x7ba3751c, 0x7c32a67c, 0x7cb82884, 37 0x7d33f0c8, 0x7da5f5a3, 0x7e0e2e31, 0x7e6c924f, 0x7ec11aa3, 0x7f0bc095, 38 0x7f4c7e52, 0x7f834ecf, 0x7fb02dc4, 0x7fd317b3, 0x7fec09e1, 0x7ffb025e, 39 0x7fffffff 40 }; 41 42 /** 43 * __fixp_sin32() returns the sin of an angle in degrees 44 * 45 * @degrees: angle, in degrees, from 0 to 360. 46 * 47 * The returned value ranges from -0x7fffffff to +0x7fffffff. 48 */ 49 static inline s32 __fixp_sin32(int degrees) 50 { 51 s32 ret; 52 bool negative = false; 53 54 if (degrees > 180) { 55 negative = true; 56 degrees -= 180; 57 } 58 if (degrees > 90) 59 degrees = 180 - degrees; 60 61 ret = sin_table[degrees]; 62 63 return negative ? -ret : ret; 64 } 65 66 /** 67 * fixp_sin32() returns the sin of an angle in degrees 68 * 69 * @degrees: angle, in degrees. The angle can be positive or negative 70 * 71 * The returned value ranges from -0x7fffffff to +0x7fffffff. 72 */ 73 static inline s32 fixp_sin32(int degrees) 74 { 75 degrees = (degrees % 360 + 360) % 360; 76 77 return __fixp_sin32(degrees); 78 } 79 80 /* cos(x) = sin(x + 90 degrees) */ 81 #define fixp_cos32(v) fixp_sin32((v) + 90) 82 83 /* 84 * 16 bits variants 85 * 86 * The returned value ranges from -0x7fff to 0x7fff 87 */ 88 89 #define fixp_sin16(v) (fixp_sin32(v) >> 16) 90 #define fixp_cos16(v) (fixp_cos32(v) >> 16) 91 92 /** 93 * fixp_sin32_rad() - calculates the sin of an angle in radians 94 * 95 * @radians: angle, in radians 96 * @twopi: value to be used for 2*pi 97 * 98 * Provides a variant for the cases where just 360 99 * values is not enough. This function uses linear 100 * interpolation to a wider range of values given by 101 * twopi var. 102 * 103 * Experimental tests gave a maximum difference of 104 * 0.000038 between the value calculated by sin() and 105 * the one produced by this function, when twopi is 106 * equal to 360000. That seems to be enough precision 107 * for practical purposes. 108 * 109 * Please notice that two high numbers for twopi could cause 110 * overflows, so the routine will not allow values of twopi 111 * bigger than 1^18. 112 */ 113 static inline s32 fixp_sin32_rad(u32 radians, u32 twopi) 114 { 115 int degrees; 116 s32 v1, v2, dx, dy; 117 s64 tmp; 118 119 /* 120 * Avoid too large values for twopi, as we don't want overflows. 121 */ 122 BUG_ON(twopi > 1 << 18); 123 124 degrees = (radians * 360) / twopi; 125 tmp = radians - (degrees * twopi) / 360; 126 127 degrees = (degrees % 360 + 360) % 360; 128 v1 = __fixp_sin32(degrees); 129 130 v2 = fixp_sin32(degrees + 1); 131 132 dx = twopi / 360; 133 dy = v2 - v1; 134 135 tmp *= dy; 136 137 return v1 + div_s64(tmp, dx); 138 } 139 140 /* cos(x) = sin(x + pi/2 radians) */ 141 142 #define fixp_cos32_rad(rad, twopi) \ 143 fixp_sin32_rad(rad + twopi / 4, twopi) 144 145 /** 146 * fixp_linear_interpolate() - interpolates a value from two known points 147 * 148 * @x0: x value of point 0 149 * @y0: y value of point 0 150 * @x1: x value of point 1 151 * @y1: y value of point 1 152 * @x: the linear interpolant 153 */ 154 static inline int fixp_linear_interpolate(int x0, int y0, int x1, int y1, int x) 155 { 156 if (y0 == y1 || x == x0) 157 return y0; 158 if (x1 == x0 || x == x1) 159 return y1; 160 161 return y0 + ((y1 - y0) * (x - x0) / (x1 - x0)); 162 } 163 164 #endif 165
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