116 lines
2.1 KiB
C
116 lines
2.1 KiB
C
/*
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* Copyright (c) 1980 Regents of the University of California.
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* All rights reserved. The Berkeley software License Agreement
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* specifies the terms and conditions for redistribution.
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*/
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#ifndef lint
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static char sccsid[] = "@(#)arc.c 1.1 94/10/31 SMI"; /* from UCB 5.2 6/23/85 */
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#endif not lint
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int del = 20;
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step(d){
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del = d;
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}
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arc(x,y,x0,y0,x1,y1){
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double pc;
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double sqrt();
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int flg,m,xc,yc,xs,ys,qs,qf;
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float dx,dy,r;
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char use;
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dx = x-x0;
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dy = y-y0;
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r = dx*dx+dy*dy;
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pc = r;
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pc = pc > 0 ? sqrt(pc) : 0;
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flg = pc/4;
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if(flg == 0)step(1);
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else if(flg < del)step(flg);
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xc = xs = x0;
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yc = ys = y0;
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move(xs,ys);
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if(x0 == x1 && y0 == y1)flg=0;
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else flg=1;
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qs = quad(x,y,x0,y0);
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qf = quad(x,y,x1,y1);
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if(abs(x-x1) < abs(y-y1)){
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use = 'x';
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if(qs == 2 || qs ==3)m = -1;
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else m=1;
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}
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else {
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use = 'y';
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if(qs > 2)m= -1;
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else m= 1;
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}
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while(1){
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switch(use){
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case 'x':
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if(qs == 2 || qs == 3)yc -= del;
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else yc += del;
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dy = yc-y;
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pc = r-dy*dy;
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xc = m*(pc > 0 ? sqrt(pc) : 0)+x;
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if((x < xs && x >= xc) || ( x > xs && x <= xc) ||
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(y < ys && y >= yc) || ( y > ys && y <= yc) )
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{
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if(++qs > 4)qs=1;
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if(qs == 2 || qs == 3)m= -1;
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else m=1;
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flg=1;
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}
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cont(xc,yc);
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xs = xc;
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ys = yc;
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if(qs == qf && flg == 1)
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switch(qf){
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case 3:
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case 4:
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if(xs >= x1)return;
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continue;
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case 1:
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case 2:
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if(xs <= x1)return;
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}
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continue;
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case 'y':
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if(qs > 2)xc += del;
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else xc -= del;
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dx = xc-x;
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pc = r-dx*dx;
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yc = m*(pc > 0 ? sqrt(pc) : 0)+y;
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if((x < xs && x >= xc) || ( x > xs && x <= xc ) ||
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(y < ys && y >= yc) || (y > ys && y <= yc) )
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{
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if(++qs > 4)qs=1;
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if(qs > 2)m = -1;
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else m = 1;
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flg=1;
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}
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cont(xc,yc);
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xs = xc;
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ys = yc;
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if(qs == qf && flg == 1)
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switch(qs){
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case 1:
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case 4:
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if(ys >= y1)return;
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continue;
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case 2:
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case 3:
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if(ys <= y1)return;
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}
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}
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}
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}
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quad(x,y,xp,yp){
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if(x < xp)
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if(y <= yp)return(1);
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else return(4);
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else if(x > xp)
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if(y < yp)return(2);
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else return(3);
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else if(y < yp)return(2);
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else return(4);
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}
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