/*
* Slide puzzle core game logic
* Copyright © 2022 Nick Bowler
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see .
*
* The RNG implementation is adapted from xoshiro256** and splitmix64
* by David Blackman and Sebastiano Vigna, originally distributed under
* the Creative Commons Zero public domain dedication.
*/
#include
#include
#include
#include
#include
#include "game.h"
#define B64(x) ((x) & 0xffffffffffffffff)
/* Rotate val left by n bits. The behaviour is undefined if n is zero. */
static unsigned long long rot_left64(unsigned long long val, int n)
{
return B64( (val << n) | (val >> (64 - n)) );
}
static unsigned long long xoshiro256ss(unsigned long long *s)
{
unsigned long long tmp, ret;
ret = B64(rot_left64(B64(s[1]*5), 7) * 9);
tmp = B64(s[1] << 17);
s[2] ^= s[0];
s[3] ^= s[1];
s[1] ^= s[2];
s[0] ^= s[3];
s[2] ^= tmp;
s[3] = rot_left64(s[3], 45);
return ret;
}
static unsigned long long splitmix64(unsigned long long *state)
{
unsigned long long z;
z = B64(*state += 0x9e3779b97f4a7c15);
z = B64((z ^ (z >> 30)) * 0xbf58476d1ce4e5b9);
z = B64((z ^ (z >> 27)) * 0x94d049bb133111eb);
return z ^ (z >> 31);
}
static unsigned long long rng_state[4];
static int rng_is_seeded(void)
{
return rng_state[0] || rng_state[1] || rng_state[2] || rng_state[3];
}
/* Calculate the least power of two greater than val, minus 1. */
static unsigned rng_mask(unsigned val)
{
val |= val >> 1;
val |= val >> 2;
val |= val >> 4;
val |= val >> 8;
if (UINT_MAX >= 65536)
val |= val >> 16;
return val;
}
/* Return a random integer uniformly on the closed interval [0, limit-1] */
static unsigned rng_uniform_int(unsigned max)
{
unsigned mask = rng_mask(max-1);
unsigned long long val;
do {
val = ( xoshiro256ss(rng_state) >> 32 ) & mask;
} while (val >= max);
return val;
}
static void shuffle(unsigned char *tiles, unsigned n)
{
unsigned i, j;
for (i = 1; i < n; i++) {
unsigned char tmp;
j = rng_uniform_int(i+1);
tmp = tiles[i];
tiles[i] = tiles[j];
tiles[j] = tmp;
}
}
void game_reseed(unsigned long long seed)
{
rng_state[0] = splitmix64(&seed);
rng_state[1] = splitmix64(&seed);
rng_state[2] = splitmix64(&seed);
rng_state[3] = splitmix64(&seed);
}
void game_reset(struct board *board)
{
unsigned char tiles[25];
unsigned i;
if (!rng_is_seeded()) {
unsigned long long seed;
seed = time(NULL);
seed += gethrxtime();
seed += seed << 32;
game_reseed(seed);
}
for (i = 0; i < 24; i++) {
tiles[i] = (i%6) + 1;
}
shuffle(tiles, 24);
memset(board->goal, 0, sizeof board->goal);
for (i = 0; i < 9; i++) {
uint_fast32_t position = board_position(i/3+1, i%3+1) >> 6;
if (tiles[i] & 1) board->goal[0] |= position;
if (tiles[i] & 2) board->goal[1] |= position;
if (tiles[i] & 4) board->goal[2] |= position;
}
tiles[24] = TILE_EMPTY;
shuffle(tiles, 25);
memset(board->game, 0, sizeof board->game);
for (i = 0; i < 25; i++) {
unsigned x = i/5, y = i%5;
uint_fast32_t position;
position = board_position(x, y);
if (tiles[i] != TILE_EMPTY) {
if (tiles[i] & 1) board->game[0] |= position;
if (tiles[i] & 2) board->game[1] |= position;
if (tiles[i] & 4) board->game[2] |= position;
} else {
board->game[3] = ~position;
board->x = x;
board->y = y;
}
}
}
int game_do_move(struct board *board, int x, int y)
{
int bx = board->x, by = board->y;
uint_least32_t mask, val[4];
int i, shl, shr;
if ((bx != x) == (by != y))
return -1;
if (bx == x) {
mask = board_mask_v(x, by, y);
shr = 5*(by < y);
shl = 5*(by > y);
} else {
mask = board_mask_h(y, bx, x);
shr = bx < x;
shl = bx > x;
}
for (i = 0; i < 4; i++) {
board->game[i] ^= (val[i] = board->game[i] & mask);
board->game[i] |= val[i] << shl >> shr;
}
board->x = x;
board->y = y;
return 0;
}
uint_fast32_t game_check_goal(struct board *board)
{
uint_least32_t *game = board->game;
uint_least16_t *goal = board->goal;
uint_least32_t mask = 0;
int i;
for (i = 0; i < 3; i++)
mask |= goal[i] ^ (game[i] >> GOAL_SHIFT);
return (mask << GOAL_SHIFT) & GOAL_MASK;
}
void game_begin(struct board *board)
{
board->time_start = gethrxtime();
}
static int_fast32_t elapsed(struct board *board)
{
return (gethrxtime() - board->time_start) / 1000000;
}
int_fast32_t game_finish(struct board *board)
{
int_fast32_t t = elapsed(board);
int i;
for (i = 0; i < 4; i++) {
board->game[i] &= GOAL_MASK;
}
/*
* Setting both x and y hole location to a bogus value will effectively
* disable the game since there will be no valid moves.
*/
board->x = board->y = -1;
return t;
}