LXR linux/include/linux/fixp-arith.h

   1#ifndef _FIXP_ARITH_H
   2#define _FIXP_ARITH_H
   3
   4#include <linux/math64.h>
   5
   6/*
   7 * Simplistic fixed-point arithmetics.
   8 * Hmm, I'm probably duplicating some code :(
   9 *
  10 * Copyright (c) 2002 Johann Deneux
  11 */
  12
  13/*
  14 * This program is free software; you can redistribute it and/or modify
  15 * it under the terms of the GNU General Public License as published by
  16 * the Free Software Foundation; either version 2 of the License, or
  17 * (at your option) any later version.
  18 *
  19 * This program is distributed in the hope that it will be useful,
  20 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22 * GNU General Public License for more details.
  23 *
  24 * You should have received a copy of the GNU General Public License
  25 * along with this program; if not, write to the Free Software
  26 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  27 *
  28 * Should you need to contact me, the author, you can do so by
  29 * e-mail - mail your message to <johann.deneux@gmail.com>
  30 */
  31
  32#include <linux/types.h>
  33
  34static const s32 sin_table[] = {
  35        0x00000000, 0x023be165, 0x04779632, 0x06b2f1d2, 0x08edc7b6, 0x0b27eb5c,
  36        0x0d61304d, 0x0f996a26, 0x11d06c96, 0x14060b67, 0x163a1a7d, 0x186c6ddd,
  37        0x1a9cd9ac, 0x1ccb3236, 0x1ef74bf2, 0x2120fb82, 0x234815ba, 0x256c6f9e,
  38        0x278dde6e, 0x29ac379f, 0x2bc750e8, 0x2ddf003f, 0x2ff31bdd, 0x32037a44,
  39        0x340ff241, 0x36185aee, 0x381c8bb5, 0x3a1c5c56, 0x3c17a4e7, 0x3e0e3ddb,
  40        0x3fffffff, 0x41ecc483, 0x43d464fa, 0x45b6bb5d, 0x4793a20f, 0x496af3e1,
  41        0x4b3c8c11, 0x4d084650, 0x4ecdfec6, 0x508d9210, 0x5246dd48, 0x53f9be04,
  42        0x55a6125a, 0x574bb8e5, 0x58ea90c2, 0x5a827999, 0x5c135399, 0x5d9cff82,
  43        0x5f1f5ea0, 0x609a52d1, 0x620dbe8a, 0x637984d3, 0x64dd894f, 0x6639b039,
  44        0x678dde6d, 0x68d9f963, 0x6a1de735, 0x6b598ea1, 0x6c8cd70a, 0x6db7a879,
  45        0x6ed9eba0, 0x6ff389de, 0x71046d3c, 0x720c8074, 0x730baeec, 0x7401e4bf,
  46        0x74ef0ebb, 0x75d31a5f, 0x76adf5e5, 0x777f903b, 0x7847d908, 0x7906c0af,
  47        0x79bc384c, 0x7a6831b8, 0x7b0a9f8c, 0x7ba3751c, 0x7c32a67c, 0x7cb82884,
  48        0x7d33f0c8, 0x7da5f5a3, 0x7e0e2e31, 0x7e6c924f, 0x7ec11aa3, 0x7f0bc095,
  49        0x7f4c7e52, 0x7f834ecf, 0x7fb02dc4, 0x7fd317b3, 0x7fec09e1, 0x7ffb025e,
  50        0x7fffffff
  51};
  52
  53/**
  54 * __fixp_sin32() returns the sin of an angle in degrees
  55 *
  56 * @degrees: angle, in degrees, from 0 to 360.
  57 *
  58 * The returned value ranges from -0x7fffffff to +0x7fffffff.
  59 */
  60static inline s32 __fixp_sin32(int degrees)
  61{
  62        s32 ret;
  63        bool negative = false;
  64
  65        if (degrees > 180) {
  66                negative = true;
  67                degrees -= 180;
  68        }
  69        if (degrees > 90)
  70                degrees = 180 - degrees;
  71
  72        ret = sin_table[degrees];
  73
  74        return negative ? -ret : ret;
  75}
  76
  77/**
  78 * fixp_sin32() returns the sin of an angle in degrees
  79 *
  80 * @degrees: angle, in degrees. The angle can be positive or negative
  81 *
  82 * The returned value ranges from -0x7fffffff to +0x7fffffff.
  83 */
  84static inline s32 fixp_sin32(int degrees)
  85{
  86        degrees = (degrees % 360 + 360) % 360;
  87
  88        return __fixp_sin32(degrees);
  89}
  90
  91/* cos(x) = sin(x + 90 degrees) */
  92#define fixp_cos32(v) fixp_sin32((v) + 90)
  93
  94/*
  95 * 16 bits variants
  96 *
  97 * The returned value ranges from -0x7fff to 0x7fff
  98 */
  99
 100#define fixp_sin16(v) (fixp_sin32(v) >> 16)
 101#define fixp_cos16(v) (fixp_cos32(v) >> 16)
 102
 103/**
 104 * fixp_sin32_rad() - calculates the sin of an angle in radians
 105 *
 106 * @radians: angle, in radians
 107 * @twopi: value to be used for 2*pi
 108 *
 109 * Provides a variant for the cases where just 360
 110 * values is not enough. This function uses linear
 111 * interpolation to a wider range of values given by
 112 * twopi var.
 113 *
 114 * Experimental tests gave a maximum difference of
 115 * 0.000038 between the value calculated by sin() and
 116 * the one produced by this function, when twopi is
 117 * equal to 360000. That seems to be enough precision
 118 * for practical purposes.
 119 *
 120 * Please notice that two high numbers for twopi could cause
 121 * overflows, so the routine will not allow values of twopi
 122 * bigger than 1^18.
 123 */
 124static inline s32 fixp_sin32_rad(u32 radians, u32 twopi)
 125{
 126        int degrees;
 127        s32 v1, v2, dx, dy;
 128        s64 tmp;
 129
 130        /*
 131         * Avoid too large values for twopi, as we don't want overflows.
 132         */
 133        BUG_ON(twopi > 1 << 18);
 134
 135        degrees = (radians * 360) / twopi;
 136        tmp = radians - (degrees * twopi) / 360;
 137
 138        degrees = (degrees % 360 + 360) % 360;
 139        v1 = __fixp_sin32(degrees);
 140
 141        v2 = fixp_sin32(degrees + 1);
 142
 143        dx = twopi / 360;
 144        dy = v2 - v1;
 145
 146        tmp *= dy;
 147
 148        return v1 +  div_s64(tmp, dx);
 149}
 150
 151/* cos(x) = sin(x + pi/2 radians) */
 152
 153#define fixp_cos32_rad(rad, twopi)      \
 154        fixp_sin32_rad(rad + twopi / 4, twopi)
 155
 156#endif
 157