~ajpaon/squell: Don't allow players to reshuffle new pieces via undo

d2cef6d561561613ff68582aa42ce15a2231d290 — Andrew Paon 1 year, 7 months ago 38085e7

Don't allow players to reshuffle new pieces via undo

Previously, when a player received new pieces they could undo and
re-place their last piece to get a new random set of pieces.

Now we use reentrant rand functions and store their state on struct
Game. When a previous version of Game is restored, so is the previous
PRNG state, thus we get the same set of pieces next time they are
refilled.

patch browse .tar.gz

1 files changed, 17 insertions(+), 8 deletions(-)

M main.c

M main.c => main.c +17 -8

@@ 262,24 262,31 @@ struct Game {
   enum GameState state;
   int score;
 
+  struct drand48_data prng_state;
+
   // player input
   int active_piece;
   int active_row;
   int active_column;
 };
 
-struct Piece random_piece() { return PIECES[random() % NPIECES]; }
+struct Piece random_piece(struct Game *g) {
+  long result;
+  lrand48_r(&g->prng_state, &result);
+
+  return PIECES[result % NPIECES];
+}
 
 void fill_table(struct Game *g) {
-  g->table[0] = random_piece();
+  g->table[0] = random_piece(g);
 
   // No duplicate pieces
   do {
-    g->table[1] = random_piece();
+    g->table[1] = random_piece(g);
   } while (g->table[0].field == g->table[1].field);
 
   do {
-    g->table[2] = random_piece();
+    g->table[2] = random_piece(g);
   } while (g->table[0].field == g->table[2].field ||
            g->table[1].field == g->table[2].field);
 }


@@ 555,10 562,6 @@ void handle_quit(int score) {
 }
 
 void game_main() {
-  long seed;
-  time(&seed);
-  srand(seed);
-
   char header[] = "                        _ _ \n"
                   "   ___  __ _ _   _  ___| | |\n"
                   "  / __|/ _` | | | |/ _ \\ | |\n"


@@ 587,6 590,12 @@ void game_main() {
 
   struct Game game = {0};
 
+  {
+    long seed;
+    time(&seed);
+    srand48_r(seed, &game.prng_state);
+  }
+
   game.state = CHOOSING_PIECE;
 
   fill_table(&game);