Extremely Fast Line Algorithm Variation E (Addition Fixed Point PreCalc)

The following is the source for the Extremely Fast Line Algorithm Variation E (Addition Fixed Point PreCalc).

```// Extremely Fast Line Algorithm Var E (Addition Fixed Point PreCalc)
// Copyright 2001-2, By Po-Han Lin
// Freely useable in non-commercial applications as long as credits
// to Po-Han Lin and link to http://www.edepot.com is provided in
// source code and can been seen in compiled executable.
//
// Lastest version at http://www.edepot.com/phl.html
// This version is for standard displays (up to 65536x65536)
// For small display version (256x256) visit http://www.edepot.com/lineex.html

// used by myLine
void myPixel(SURFACE* surface, int x,int y) {
// PLOT x,y point on surface

}

// THE EXTREMELY FAST LINE ALGORITHM Variation E (Addition Fixed Point PreCalc)
void myLine(SURFACE* surface, int x, int y, int x2, int y2) {
bool yLonger=false;
int shortLen=y2-y;
int longLen=x2-x;
if (abs(shortLen)>abs(longLen)) {
int swap=shortLen;
shortLen=longLen;
longLen=swap;
yLonger=true;
}
int decInc;
if (longLen==0) decInc=0;
else decInc = (shortLen << 16) / longLen;

if (yLonger) {
if (longLen>0) {
longLen+=y;
for (int j=0x8000+(x<<16);y<=longLen;++y) {
myPixel(surface,j >> 16,y);
j+=decInc;
}
return;
}
longLen+=y;
for (int j=0x8000+(x<<16);y>=longLen;--y) {
myPixel(surface,j >> 16,y);
j-=decInc;
}
return;
}

if (longLen>0) {
longLen+=x;
for (int j=0x8000+(y<<16);x<=longLen;++x) {
myPixel(surface,x,j >> 16);
j+=decInc;
}
return;
}
longLen+=x;
for (int j=0x8000+(y<<16);x>=longLen;--x) {
myPixel(surface,x,j >> 16);
j-=decInc;
}

}

void mySquare(SURFACE* surface,int x, int y, int x2, int y2) {
myLine(surface,x,y,x2,y2);
myLine(surface,x2,y2,x2+(y-y2),y2+(x2-x));
myLine(surface,x,y,x+(y-y2),y+(x2-x));
myLine(surface,x+(y-y2),y+(x2-x),x2+(y-y2),y2+(x2-x));
}

void myRect(SURFACE* surface, int x, int y, int x2, int y2) {
myLine(surface,x,y,x2,y);
myLine(surface,x2,y,x2,y2);
myLine(surface,x2,y2,x,y2);
myLine(surface,x,y2,x,y);
}

```