donut_nomathlib_deobfuscated.c

/* This is the deobfuscated version of the optimized donut.c code by
 * Andy Sloane (@a1k0n).
 * 
 * Taken from:
 * https://www.a1k0n.net/2021/01/13/optimizing-donut.html
 * 
 * Additionally, I have fixed warnings raised by the compiler.
 */

#include <string.h>
#include <stdio.h>
#include <unistd.h>

int x,y,o,N;

#define R(t, x, y) \
    f = x; \
    x -= t * y; \
    y += t * f; \
    f = (3 - x * x - y * y) / 2; \
    x *= f; \
    y *= f;

int main()
{
    float z[1760], a = 0, e = 1, c = 1, d = 0, f, g, h, G, H, A, t, D;
    char b[1760];

    for(;;) {
        memset(b, 32, 1760);
        memset(z, 0, 7040);

        g = 0, h = 1;

        for(int j = 0; j < 90; j++){
            G = 0, H = 1;
            for (int i = 0; i < 314; i++) {
                A = h + 2;
                D = 1 / (G * A * a + g * e+5);
                t = G * A * e - g * a;
                x = 40 + 30 * D * (H * A * d - t * c);
                y = 12 + 15 * D * (H * A * c + t * d);
                o = x + 80 * y;
                N = 8 * ((g * a - G * h * e) * d - G * h * a - g * e - H * h * c);
                if (22 > y && y > 0 && x > 0 && 80 > x && D > z[o]) {
                    z[o] = D;
                    b[o] = (N>0?N:0)[".,-~:;=!*#$@"];
                }
                R(.02, H, G);
            }
            R(.07, h, g);
        }

        for(int k = 0; 1761 > k; k++)
            putchar( k % 80 ? b[k] : 10);

        R(.04, e, a);
        R(.02, d, c);

        usleep(15000);

        printf('\n' + (" donut.c! \x1b[23A"));
    }
    return 0;
}