linux/include/linux/fixp-arith.h
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   1#ifndef _FIXP_ARITH_H
   2#define _FIXP_ARITH_H
   3
   4/*
   5 * Simplistic fixed-point arithmetics.
   6 * Hmm, I'm probably duplicating some code :(
   7 *
   8 * Copyright (c) 2002 Johann Deneux
   9 */
  10
  11/*
  12 * This program is free software; you can redistribute it and/or modify
  13 * it under the terms of the GNU General Public License as published by
  14 * the Free Software Foundation; either version 2 of the License, or
  15 * (at your option) any later version.
  16 *
  17 * This program is distributed in the hope that it will be useful,
  18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20 * GNU General Public License for more details.
  21 *
  22 * You should have received a copy of the GNU General Public License
  23 * along with this program; if not, write to the Free Software
  24 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  25 *
  26 * Should you need to contact me, the author, you can do so by
  27 * e-mail - mail your message to <johann.deneux@gmail.com>
  28 */
  29
  30#include <linux/types.h>
  31
  32/* The type representing fixed-point values */
  33typedef s16 fixp_t;
  34
  35#define FRAC_N 8
  36#define FRAC_MASK ((1<<FRAC_N)-1)
  37
  38/* Not to be used directly. Use fixp_{cos,sin} */
  39static const fixp_t cos_table[46] = {
  40        0x0100, 0x00FF, 0x00FF, 0x00FE, 0x00FD, 0x00FC, 0x00FA, 0x00F8,
  41        0x00F6, 0x00F3, 0x00F0, 0x00ED, 0x00E9, 0x00E6, 0x00E2, 0x00DD,
  42        0x00D9, 0x00D4, 0x00CF, 0x00C9, 0x00C4, 0x00BE, 0x00B8, 0x00B1,
  43        0x00AB, 0x00A4, 0x009D, 0x0096, 0x008F, 0x0087, 0x0080, 0x0078,
  44        0x0070, 0x0068, 0x005F, 0x0057, 0x004F, 0x0046, 0x003D, 0x0035,
  45        0x002C, 0x0023, 0x001A, 0x0011, 0x0008, 0x0000
  46};
  47
  48
  49/* a: 123 -> 123.0 */
  50static inline fixp_t fixp_new(s16 a)
  51{
  52        return a<<FRAC_N;
  53}
  54
  55/* a: 0xFFFF -> -1.0
  56      0x8000 -> 1.0
  57      0x0000 -> 0.0
  58*/
  59static inline fixp_t fixp_new16(s16 a)
  60{
  61        return ((s32)a)>>(16-FRAC_N);
  62}
  63
  64static inline fixp_t fixp_cos(unsigned int degrees)
  65{
  66        int quadrant = (degrees / 90) & 3;
  67        unsigned int i = degrees % 90;
  68
  69        if (quadrant == 1 || quadrant == 3)
  70                i = 90 - i;
  71
  72        i >>= 1;
  73
  74        return (quadrant == 1 || quadrant == 2)? -cos_table[i] : cos_table[i];
  75}
  76
  77static inline fixp_t fixp_sin(unsigned int degrees)
  78{
  79        return -fixp_cos(degrees + 90);
  80}
  81
  82static inline fixp_t fixp_mult(fixp_t a, fixp_t b)
  83{
  84        return ((s32)(a*b))>>FRAC_N;
  85}
  86
  87#endif
  88
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