110 lines
2.5 KiB
C
110 lines
2.5 KiB
C
/***
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**
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** Module: Trig
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**
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** Description:
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** This is a module of the T1 to TT font converter. The module
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** contains a look-up table for computing atan2() faster, and
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** with less precision than that of the c run-time library.
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**
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** Author: Michael Jansson
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**
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** Created: 5/26/93
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**
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***/
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#include "types.h"
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#include "metrics.h"
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#include "trig.h"
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static const unsigned char atan_tbl[] = {
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0,
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2, 5, 7, 10, 12, 15, 17, 20, 22, 25, 27, 30, 32, 35, 38, 40,
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43, 45, 48, 50, 53, 55, 57, 60, 62, 65, 67, 70, 72, 75, 77, 79,
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82, 84, 87, 89, 91, 94, 96, 98, 101, 103, 105, 107, 110, 112, 114, 116,
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119, 121, 123, 125, 127, 130, 132, 134, 136, 138, 140, 142, 144, 147, 149, 151,
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153, 155, 157, 159, 161, 163, 165, 167, 168, 170, 172, 174, 176, 178, 180, 182,
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183, 185, 187, 189, 191, 192, 194, 196, 198, 199, 201, 203, 204, 206, 208, 209,
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211, 212, 214, 216, 217, 219, 220, 222, 223, 225, 226, 228, 229, 231, 232, 234,
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235, 237, 238, 239, 241, 242, 244, 245, 246, 248, 249, 250, 252, 253, 254, 255
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};
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/***
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** Function: Atan2
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**
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** Description:
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** Compute atan2()
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***/
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int FASTCALL Atan2(const funit dy, const funit dx)
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{
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funit du, dv;
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int a = 0;
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/* Normalize the sign. */
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if (ABS(dx)>ABS(dy)) {
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du = ABS(dx);
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dv = ABS(dy);
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if (du==0) {
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a = PI4;
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} else {
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/* Normalize for the size of the table. */
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while (dv>256) {
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dv = (dv+1)>>1;
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du = (du+1)>>1;
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}
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dv = ((dv<<7)+(du>>1))/du;
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/* Lookup the angle. */
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if (dv==1)
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a = (int)((long)PI4 * (long)ABS(dx) / (long)ABS(dy));
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if (du!=dv)
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a = (int)atan_tbl[dv];
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}
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} else {
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du = ABS(dy);
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dv = ABS(dx);
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if (du==0) {
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a = PI4;
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} else {
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/* Normalize for the size of the table. */
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while (dv>256) {
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dv = (dv+1)>>1;
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du = (du+1)>>1;
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}
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dv = ((dv<<7)+(du>>1))/du;
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/* Lookup the angle. */
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if (dv==1)
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a = (int)((long)PI4 * (long)ABS(dy) / (long)ABS(dx));
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if (du!=dv)
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a = PI2 - (int)atan_tbl[dv];
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}
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}
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/* pick the right quadrant. */
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if (dx>0) {
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if (dy>0) {
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/* NOOP */
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} else {
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a = -a;
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}
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} else {
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if (dy>0) {
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a = PI - a;
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} else {
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a = a - PI;
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}
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}
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return a;
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}
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