include/linux/fixp-arith.h

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