Cellular automata :D

////////////////////////////////////////////////////////////////////////////////
// THE SCOTCH-WARE LICENSE (Revision 0):
// <aaronryool/gmail.com> wrote this file. As long as you retain this notice you
// can do whatever you want with this stuff. If we meet some day, and you think
// this stuff is worth it, you can buy me a shot of scotch in return
////////////////////////////////////////////////////////////////////////////////

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <signal.h>

typedef enum { false, true } bool;

#define BGBLACK  "\033[40m"
#define BGRED    "\033[41m"
#define BGWHITE  "\033[47m"
#define RESET    "\033[0m"

#define CLEAR           "\033[2J"
#define HIDE_CURSOR     "\e[?25l"
#define SHOW_CURSOR     "\e[?25h"

#define CURSOR(x, y) printf("\033[%i;%iH\n", y, x)

void __attribute__((noreturn)) usage(char** argv)
{
    printf("%s <#frames>\n", argv[0]);
    exit(1);
}

void init(int argc, char** argv, char** envp)
{
    if(argc != 2)
        usage(argv);
    printf("%s", HIDE_CURSOR);
    signal(SIGINT, exit);
}

void fini()
{
    printf("%s", SHOW_CURSOR);
}

__attribute__((section(".init_array"))) typeof(init)* __init = init;
__attribute__((section(".fini_array"))) typeof(fini)* __fini = fini;

int grid_check_neighbors(bool* grid, int width, int height, int x, int y)
{
#define SIZE (width * height)
#define STATE(x, y, limit_comp) (int) (((x) * width + (y)) limit_comp ? grid[(x) * width + (y)] : false)
    return STATE(x-1, y-1,>=0) + STATE(x-1,y,>=0) + STATE(x-1,y+1,>=0) + STATE(x,y-1,>=0) +
        STATE(x,y+1,<SIZE) + STATE(x+1,y-1,<SIZE) + STATE(x+1,y,<SIZE) + STATE(x+1,y+1,<SIZE);
}


void grid_step(bool* grid, int width, int height)
{
#define SIZE (width * height)
    unsigned int i, n;
    bool t[SIZE];
    memcpy(t, grid, SIZE*sizeof(bool));
    for(i = 0;i < SIZE;i++)
    {
        n = grid_check_neighbors(grid, width, height, i / width, i % width);
        if(!grid[i] && n == 3)
                t[i] = true;
        else if(n < 2 || n > 3)
                t[i] = false;
    }
    memcpy(grid, t, SIZE*sizeof(bool));
}

int main(int argc, char** argv, char** envp)
{
#define SIZE (width * height)
    const int width = 25,
        height = 25;
    int i, c;
    unsigned int frames = atoi(argv[1]);

    if(! frames) usage(argv);

    bool grid[] = {
        0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
        0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
        0,0,0,0,0,0,1,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
        0,0,0,0,0,0,1,1,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
        0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
        0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
        0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,0,0,0,0,
        0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,
        0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,
        0,0,0,0,0,1,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,
        0,0,0,0,1,0,1,0,0,0,0,1,1,1,0,0,0,0,0,0,0,0,0,0,0,
        0,0,0,0,0,1,0,0,0,0,0,1,0,1,0,0,0,0,0,0,0,0,0,0,0,
        0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,
        0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,
        0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,0,0,
        0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
        0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
        0,0,0,1,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,
        0,0,0,1,1,1,0,0,0,0,0,0,1,1,1,0,0,0,0,0,0,0,0,0,0,
        0,0,0,0,0,0,0,0,0,0,0,0,1,0,1,0,0,0,0,0,0,0,0,0,0,
        0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
        0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
        0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
        0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
        0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
    };

    printf("%s", CLEAR);
    for(i = 0;i < frames;i++)
    {
        CURSOR(0, 0);
        for(c = 0;c < SIZE;c++)
        {
            printf(grid[c] ? "  %s" : "  %s", grid[c] ? BGRED : c % 2 ? BGBLACK : BGWHITE);
            if((c + 1) % width == 0)
                printf("%s\n", RESET);
        }
        grid_step(grid, width, height);
        usleep(1000*100);
    }
    return 0;
}