harvey/sys/src/libdraw/icossin.c

/*
 * This file is part of the UCB release of Plan 9. It is subject to the license
 * terms in the LICENSE file found in the top-level directory of this
 * distribution and at http://akaros.cs.berkeley.edu/files/Plan9License. No
 * part of the UCB release of Plan 9, including this file, may be copied,
 * modified, propagated, or distributed except according to the terms contained
 * in the LICENSE file.
 */

#include	<u.h>
#include	<libc.h>
#include	<draw.h>

/*
 * Integer sine and cosine for integral degree argument.
 * Tables computed by (sin,cos)(PI*d/180).
 */
static int16_t sinus[91] = {
	0,	/* 0 */
	18,	/* 1 */
	36,	/* 2 */
	54,	/* 3 */
	71,	/* 4 */
	89,	/* 5 */
	107,	/* 6 */
	125,	/* 7 */
	143,	/* 8 */
	160,	/* 9 */
	178,	/* 10 */
	195,	/* 11 */
	213,	/* 12 */
	230,	/* 13 */
	248,	/* 14 */
	265,	/* 15 */
	282,	/* 16 */
	299,	/* 17 */
	316,	/* 18 */
	333,	/* 19 */
	350,	/* 20 */
	367,	/* 21 */
	384,	/* 22 */
	400,	/* 23 */
	416,	/* 24 */
	433,	/* 25 */
	449,	/* 26 */
	465,	/* 27 */
	481,	/* 28 */
	496,	/* 29 */
	512,	/* 30 */
	527,	/* 31 */
	543,	/* 32 */
	558,	/* 33 */
	573,	/* 34 */
	587,	/* 35 */
	602,	/* 36 */
	616,	/* 37 */
	630,	/* 38 */
	644,	/* 39 */
	658,	/* 40 */
	672,	/* 41 */
	685,	/* 42 */
	698,	/* 43 */
	711,	/* 44 */
	724,	/* 45 */
	737,	/* 46 */
	749,	/* 47 */
	761,	/* 48 */
	773,	/* 49 */
	784,	/* 50 */
	796,	/* 51 */
	807,	/* 52 */
	818,	/* 53 */
	828,	/* 54 */
	839,	/* 55 */
	849,	/* 56 */
	859,	/* 57 */
	868,	/* 58 */
	878,	/* 59 */
	887,	/* 60 */
	896,	/* 61 */
	904,	/* 62 */
	912,	/* 63 */
	920,	/* 64 */
	928,	/* 65 */
	935,	/* 66 */
	943,	/* 67 */
	949,	/* 68 */
	956,	/* 69 */
	962,	/* 70 */
	968,	/* 71 */
	974,	/* 72 */
	979,	/* 73 */
	984,	/* 74 */
	989,	/* 75 */
	994,	/* 76 */
	998,	/* 77 */
	1002,	/* 78 */
	1005,	/* 79 */
	1008,	/* 80 */
	1011,	/* 81 */
	1014,	/* 82 */
	1016,	/* 83 */
	1018,	/* 84 */
	1020,	/* 85 */
	1022,	/* 86 */
	1023,	/* 87 */
	1023,	/* 88 */
	1024,	/* 89 */
	1024,	/* 90 */
};

void
icossin(int deg, int *cosp, int *sinp)
{
	int sinsign, cossign;
	int16_t *stp, *ctp;

	deg %= 360;
	if(deg < 0)
		deg += 360;
	sinsign = 1;
	cossign = 1;
	stp = 0;
	ctp = 0;
	switch(deg/90){
	case 2:
		sinsign = -1;
		cossign = -1;
		deg -= 180;
		/* fall through */
	case 0:
		stp = &sinus[deg];
		ctp = &sinus[90-deg];
		break;
	case 3:
		sinsign = -1;
		cossign = -1;
		deg -= 180;
		/* fall through */
	case 1:
		deg = 180-deg;
		cossign = -cossign;
		stp = &sinus[deg];
		ctp = &sinus[90-deg];
		break;
	}
	*sinp = sinsign*stp[0];
	*cosp = cossign*ctp[0];
}