ref: c8a7747659c6b8aa4989cfcccf518cbe18d9182d
dir: /sys/src/libdraw/icossin.c/
#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 short 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;
short *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];
}