Game of Life (in C/SDL)

game_of_life.c

#include "SDL.h"
#include <stdint.h>
#include <stdbool.h>
#include <stdlib.h>
#include <unistd.h>
#include <time.h>

#define SIZE 1000

struct cell {
    bool is_alive;
    int8_t nbc_prev;
    int8_t nbc_next;
};

void sync_neighbors(struct cell *board) {
    for (int i = 0; i < (SIZE * SIZE); i++) {
        board[i].nbc_prev = board[i].nbc_next;
    }
}

void update_neightbors(struct cell *board, int idx, int delta) {
    int offs[] = {-SIZE-1, -SIZE, -SIZE+1, -1, +1, SIZE-1, SIZE, SIZE+1};
    for (int offs_i = 0; offs_i < 8; offs_i++) {
        board[(idx + offs[offs_i]) % (SIZE * SIZE)].nbc_next += delta;
    }
}

void step(struct cell *board) {
    int cellsize = sizeof(struct cell);
    for (int i = 0; i < (SIZE * SIZE); i++) {
        struct cell *c = board + i;
        if (c->is_alive) {
            if (c->nbc_prev <= 1 || c->nbc_prev >= 4) {
                c->is_alive = false;
                update_neightbors(board, i, -1);
            }
        } else {
            if (c->nbc_prev == 3) {
                c->is_alive = true;
                update_neightbors(board, i, 1);
            }
        }
    }
    sync_neighbors(board);
}

void randomize(struct cell *board) {
    srand(time(NULL));

    for (int i = 0; i < (SIZE * SIZE); i++) {
        // int r = rand() % 20;
        // if (r < 1) {
        //     board[i].is_alive = true;
        //     update_neightbors(board, i, 1);
        // }

        if (i % 3 == 0) {
            board[i].is_alive = true;
            update_neightbors(board, i, 1);
        }
    }

    sync_neighbors(board);
}

void draw(struct cell *board, SDL_Renderer *renderer) {
    SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
    SDL_RenderClear(renderer);

    SDL_SetRenderDrawColor(renderer, 255, 255, 255, 255);
    for (int y = 0; y < SIZE; y++) {
        for (int x = 0; x < SIZE; x++) {
            int i = y * SIZE + x;
            if (!board[i].is_alive) continue;

            SDL_Rect point = {x, y, 1, 1};
            SDL_RenderFillRect(renderer, &point);
        }
    }
}

int main(int argc, char* argv[]) {
    if (SDL_Init(SDL_INIT_VIDEO) != 0) {
        printf("SDL Init Error\n");
        exit(EXIT_FAILURE);
    }

    SDL_Window *win = SDL_CreateWindow("Game Of Life", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, SIZE, SIZE, SDL_WINDOW_SHOWN);
    if (win == NULL) {
        printf("Window creation error\n");
        exit(EXIT_FAILURE);
    }

    SDL_Renderer *renderer = SDL_CreateRenderer(win, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC);
    if (renderer == NULL) {
        printf("Renderer creation error\n");
        exit(EXIT_FAILURE);
    }

    struct cell *board = malloc(sizeof(struct cell) * (SIZE * SIZE));
    if (board == NULL) {
        printf("Malloc error\n");
        exit(EXIT_FAILURE);
    }

    memset(board, 0, sizeof(struct cell) * (SIZE * SIZE));

    randomize(board);

    bool quit = false;
    while (!quit) {
        step(board);

        draw(board, renderer);

        SDL_RenderPresent(renderer);
        SDL_Delay(10);

        SDL_Event e;
        while (SDL_PollEvent(&e)) {
            if (e.type == SDL_MOUSEBUTTONDOWN) quit = true;
        }
     }

    SDL_Quit();

    free(board);
}