simpleSnakeSDL.cpp

// very simple SDL snake implementation

#include "SDL/SDL.h"
#include <iostream>

const int squareSize=10;
const int squares=30;
const int hsquares=squares/2;
const int size=squareSize*squares;

const int startingSize = 3;
// const int vSquares=30;

struct point {
	int x, y;
};

point centerpoint = {hsquares, hsquares};

struct node {
	point p;
	node *next, *prev;
};

class snake {
	point food;
	node *tail, *head;
	int size, dir;
	public:
	snake(){
		size = startingSize;
		dir = 0;
		// init snake
		head = new node;
		head->p = centerpoint;
		head->prev = NULL;
		node *aux = new node;
		head->next = aux;
		aux->prev = head;
		for (int i=1; i<size; i++) {
			aux->p = centerpoint;
			aux->next = new node;
			aux->next->prev = aux;
			aux = aux->next;
		}
		tail = aux;
		tail->next = NULL;
		tail->p = centerpoint;
		placefood();
	}
	void placefood(){
		bool col;
		do {
			food.x = rand() % squares;
			food.y = rand() % squares;

			node *aux = head;
			col = false;
			do {
				col = (aux->p.x == food.x && aux->p.y == food.y);
				aux = aux->next;
			} while (aux && !col);
		} while (col);
	}
	void draw(SDL_Surface *screen){
		node *prev = tail;
		do {
			SDL_Rect *pos = new SDL_Rect;
			pos->x = prev->p.x * squareSize;
			pos->y = prev->p.y * squareSize;
			pos->w = pos->h = squareSize;
			SDL_FillRect(screen, pos,	SDL_MapRGBA(screen->format, 255,255,255,255));
			prev=prev->prev;
		} while (prev!=NULL);

		SDL_Rect *foodp = new SDL_Rect;
		foodp->x = food.x * squareSize;
		foodp->y = food.y * squareSize;
		foodp->w = foodp->h = squareSize;
		SDL_FillRect(screen, foodp, SDL_MapRGBA(screen->format, 255, 0, 0, 255));
	}
	void print() {
		node *curr = head;
		do {
			std::cout<<curr->p.x<<';'<<curr->p.y<<';'<<curr->prev<<';'<<curr->next<<' ';
			curr = curr->next;
		} while (curr!=NULL);
		std::cout<<'\n';
	}
	bool move() {
		tail->prev->next = NULL;

		node *aux = tail;
		tail = tail->prev;

		aux->prev = NULL;
		aux->next = head;
		head->prev = aux;

		aux->p = head->p;
		head = aux;

		switch (dir) {
			case 0:
				if (head->p.x + 2 > squares)
					head->p.x = 0;
				else head->p.x += 1;
				break;
			case 1:
				if (head->p.y + 2 > squares)
					head->p.y = 0;
				else head->p.y += 1;
				break;
			case 2:
				if (head->p.x == 0)
					head->p.x = squares - 1;
				else head->p.x -= 1;
				break;
			default:
				if (head->p.y == 0)
					head->p.y = squares - 1;
				else head->p.y -= 1;
		}
		
		// print();

		aux = aux->next;
		do {
		 	if (aux->p.x == head->p.x && aux->p.y == head->p.y) {
				std::cout<<"GAME OVER - "<<size<<" points\n";
				return false;
		 	}
			aux = aux->next;
		} while (aux);

		if (head->p.x == food.x && head->p.y == food.y) {
			node * newtail = new node;
			newtail->prev = tail;
			newtail->p = tail->p;
			tail->next = newtail;
			tail = newtail;
			size++;
			placefood();
		}

		return true;
	}
	void changedir(int _dir) {
		if ((dir == 0 && _dir == 2) ||
				(dir == 1 && _dir == 3) ||
				(dir == 2 && _dir == 0) ||
				(dir == 3 && _dir == 1)) return;
		dir = _dir;
	}
};

int main() {
	if (SDL_Init(SDL_INIT_EVERYTHING)) {
		std::cout<<"Could not initialize SDL.\n";
		return 1;
	};
	
	SDL_Surface* screen = SDL_SetVideoMode(
		size,size,0,SDL_HWSURFACE|SDL_DOUBLEBUF);

	snake s;
	// s.print();
	int lt = SDL_GetTicks(), lm = lt;
	

	bool active=true;
	while(active){
	
		// RENDER
		SDL_FillRect(screen, NULL, SDL_MapRGBA(screen->format,0,0,0,255));
		s.draw(screen);
		// draw food


		SDL_Flip(screen);
		SDL_Event ev;
		while(SDL_PollEvent(&ev)) {
			switch (ev.type) {
				case SDL_QUIT:
					active = false;
					break;
				case SDL_KEYDOWN:
					switch ((int)ev.key.keysym.scancode) {
						case 114:
							s.changedir(0);
							break;
						case 116:
							s.changedir(1);
							break;
						case 113:
							s.changedir(2);
							break;
						case 111:
							s.changedir(3);
					}
					// std::cout<<(int)ev.key.keysym.scancode<<'\n';
					// std::cout.flush();
			}
		}

		int ct = SDL_GetTicks();
		if (ct - lt >= 60) {
			lt = ct;
			active = s.move();
			// s.print();
		}
	}

	return 0;
}