91 lines
2.2 KiB
C
91 lines
2.2 KiB
C
#ifndef _FIXP_ARITH_H
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#define _FIXP_ARITH_H
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/*
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* $$
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*
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* Simplistic fixed-point arithmetics.
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* Hmm, I'm probably duplicating some code :(
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*
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* Copyright (c) 2002 Johann Deneux
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*/
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/*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*
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* Should you need to contact me, the author, you can do so by
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* e-mail - mail your message to <deneux@ifrance.com>
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*/
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#include <linux/types.h>
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// The type representing fixed-point values
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typedef s16 fixp_t;
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#define FRAC_N 8
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#define FRAC_MASK ((1<<FRAC_N)-1)
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// Not to be used directly. Use fixp_{cos,sin}
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static const fixp_t cos_table[45] = {
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0x0100, 0x00FF, 0x00FF, 0x00FE, 0x00FD, 0x00FC, 0x00FA, 0x00F8,
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0x00F6, 0x00F3, 0x00F0, 0x00ED, 0x00E9, 0x00E6, 0x00E2, 0x00DD,
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0x00D9, 0x00D4, 0x00CF, 0x00C9, 0x00C4, 0x00BE, 0x00B8, 0x00B1,
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0x00AB, 0x00A4, 0x009D, 0x0096, 0x008F, 0x0087, 0x0080, 0x0078,
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0x0070, 0x0068, 0x005F, 0x0057, 0x004F, 0x0046, 0x003D, 0x0035,
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0x002C, 0x0023, 0x001A, 0x0011, 0x0008
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};
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/* a: 123 -> 123.0 */
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static inline fixp_t fixp_new(s16 a)
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{
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return a<<FRAC_N;
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}
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/* a: 0xFFFF -> -1.0
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0x8000 -> 1.0
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0x0000 -> 0.0
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*/
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static inline fixp_t fixp_new16(s16 a)
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{
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return ((s32)a)>>(16-FRAC_N);
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}
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static inline fixp_t fixp_cos(unsigned int degrees)
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{
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int quadrant = (degrees / 90) & 3;
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unsigned int i = degrees % 90;
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if (quadrant == 1 || quadrant == 3) {
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i = 89 - i;
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}
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i >>= 1;
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return (quadrant == 1 || quadrant == 2)? -cos_table[i] : cos_table[i];
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}
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static inline fixp_t fixp_sin(unsigned int degrees)
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{
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return -fixp_cos(degrees + 90);
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}
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static inline fixp_t fixp_mult(fixp_t a, fixp_t b)
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{
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return ((s32)(a*b))>>FRAC_N;
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}
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#endif
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