X-Git-Url: http://git.draconx.ca/gitweb/rrace.git/blobdiff_plain/48cf657b615567153e5ed786b6034f9b46733f9a..bb0ef256f417d9847b157c0a204a634d65c98a4b:/src/game.c

diff --git a/src/game.c b/src/game.c
index 999d526..ab70478 100644
--- a/src/game.c
+++ b/src/game.c
@@ -1,6 +1,6 @@
 /*
  * Slide puzzle core game logic
- * Copyright © 2022 Nick Bowler
+ * Copyright © 2022-2023 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
@@ -23,8 +23,8 @@
 #include <config.h>
 #include <limits.h>
 #include <string.h>
+#include <unistd.h>
 #include <time.h>
-#include <gethrxtime.h>
 #include "game.h"
 
 #define B64(x) ((x) & 0xffffffffffffffff)
@@ -119,6 +119,12 @@ void game_reseed(unsigned long long seed)
 	rng_state[3] = splitmix64(&seed);
 }
 
+#define assign_tile(planes, tile, bit) do { \
+	0[planes] |= (((tile)>>0) & 1ul) << (bit); \
+	1[planes] |= (((tile)>>1) & 1ul) << (bit); \
+	2[planes] |= (((tile)>>2) & 1ul) << (bit); \
+} while (0)
+
 void game_reset(struct board *board)
 {
 	unsigned char tiles[25];
@@ -127,8 +133,19 @@ void game_reset(struct board *board)
 	if (!rng_is_seeded()) {
 		unsigned long long seed;
 
-		seed = time(NULL);
-		seed += gethrxtime();
+		/*
+		 * Try to get a reasonable initial seed.
+		 *
+		 * Reasonable in this context means:
+		 *
+		 * - roughly even distribution of 1/0 bits, and
+		 * - unlikely to generate the same seed twice in succession.
+		 */
+		game_begin(board);
+
+		seed  = time(NULL);
+		seed += board->time_start;
+		seed += (unsigned long long)getpid() << 16;
 		seed += seed << 32;
 
 		game_reseed(seed);
@@ -141,33 +158,55 @@ void game_reset(struct board *board)
 	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;
+	/*
+	 * Goal bitmap has 2-tile "gaps" between rows; it doesn't matter what
+	 * these are set to and since we have a random permutation it doesn't
+	 * matter which of the 24 nonempty tiles we pick for the actual goal.
+	 */
+	for (i = 0; i < 13; i++) {
+		assign_tile(board->goal, tiles[i], i);
 	}
 
 	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;
+		assign_tile(board->game, tiles[i], i);
+
+		if (tiles[i] == TILE_EMPTY) {
+			board->game[3] = (1ul<<i);
+			board->x = i%5;
+			board->y = i/5;
 		}
 	}
+
+/* Uncomment to make every game stupidly easy -- winnable in 1 move */
+#if 0
+	/* Force empty space to the border */
+	if (board_position(board->x, board->y) & GOAL_MASK) {
+		switch (rng_uniform_int(4)) {
+		case 0: game_do_move(board, board->x, 0); break;
+		case 1: game_do_move(board, board->x, 4); break;
+		case 2: game_do_move(board, 0, board->y); break;
+		case 3: game_do_move(board, 4, board->y); break;
+		}
+	}
+
+	/* Force goal to match the current board */
+	for (i = 0; i < 3; i++) {
+		board->goal[i] = (board->game[i] & GOAL_MASK) >> GOAL_SHIFT;
+	}
+
+	/* Move empty space back to the centre */
+	if (board->x == 0 || board->x == 4) {
+		game_do_move(board, 1+rng_uniform_int(3), board->y);
+	}
+
+	if (board->y == 0 || board->y == 4) {
+		game_do_move(board, board->x, 1+rng_uniform_int(3));
+	}
+#endif
 }
 
 uint_fast32_t game_do_move(struct board *board, int x, int y)
@@ -209,23 +248,13 @@ uint_fast32_t game_check_goal(struct board *board)
 	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;
+		mask |= game[i] ^ ((0ul+goal[i]) << GOAL_SHIFT);
+	return mask & GOAL_MASK;
 }
 
 int_fast32_t game_finish(struct board *board)
 {
-	int_fast32_t t = elapsed(board);
+	int_fast32_t t = game_elapsed(board);
 	int i;
 
 	for (i = 0; i < 4; i++) {