From: Holger Schemel <info@artsoft.org>
Date: Thu, 10 Sep 2020 18:19:20 +0000 (+0200)
Subject: added handling 64-bit random value bug with old tapes in EM engine
X-Git-Tag: 4.2.0.3~55
X-Git-Url: https://git.artsoft.org/?a=commitdiff_plain;h=1006b2db;p=rocksndiamonds.git

added handling 64-bit random value bug with old tapes in EM engine

See commits 61c3da0 (incomplete fix) and c92edfe9 (final fix) for
details about this problem that was introduced (by a partial fix) in
version 3.3.1.0 and finally fixed in version 4.0.1.2, which resulted
in many tapes recorded between these versions with the EM game engine
to be broken.

To fix these broken tapes, it is required to set a new property bit in
all existing tape files that are affected by this bug.

The functionality to automatically patch these tapes will be added as
a new command line option.
---

diff --git a/src/game.c b/src/game.c
index 3544dcf7..ea44ebd1 100644
--- a/src/game.c
+++ b/src/game.c
@@ -2990,6 +2990,9 @@ static void InitGameEngine(void)
   game_em.use_snap_key_bug =
     (game.engine_version < VERSION_IDENT(4,0,1,0));
 
+  game_em.use_random_bug =
+    (tape.property_bits & TAPE_PROPERTY_EM_RANDOM_BUG);
+
   boolean use_old_em_engine = (game.engine_version < VERSION_IDENT(4,2,0,0));
 
   game_em.use_old_explosions		= use_old_em_engine;
diff --git a/src/game_em/convert.c b/src/game_em/convert.c
index 99381064..2ea8e962 100644
--- a/src/game_em/convert.c
+++ b/src/game_em/convert.c
@@ -461,6 +461,7 @@ void prepare_em_level(void)
   //
   // - game_em.use_single_button (default: TRUE)
   // - game_em.use_snap_key_bug (default: FALSE)
+  // - game_em.use_random_bug (default: FALSE)
   // - game_em.use_old_explosions (default: FALSE)
   // - game_em.use_old_android (default: FALSE)
   // - game_em.use_old_push_elements (default: FALSE)
diff --git a/src/game_em/export.h b/src/game_em/export.h
index 51401e67..c5373fdb 100644
--- a/src/game_em/export.h
+++ b/src/game_em/export.h
@@ -45,6 +45,7 @@ struct GameInfo_EM
   // flags to handle bugs in and changes between different engine versions
   boolean use_single_button;
   boolean use_snap_key_bug;
+  boolean use_random_bug;
   boolean use_old_explosions;
   boolean use_old_android;
   boolean use_old_push_elements;
diff --git a/src/game_em/logic.c b/src/game_em/logic.c
index 68a977aa..ba823a0c 100644
--- a/src/game_em/logic.c
+++ b/src/game_em/logic.c
@@ -12,6 +12,8 @@
 #define ACID_ROLL	/* rolling objects go into acid rather than remove it */
 #define ACID_PLAYER	/* player gets killed by acid, but without explosion */
 
+#define RANDOM_BUG	/* handle problem with old tapes using 64-bit random */
+
 #define RANDOM(x)	((seed = seed << 31 | seed >> 1) % x)
 
 static short **cave, **next, **boom;
@@ -7485,7 +7487,11 @@ static void logic_globals(void)
   int x;
   int y;
   int count;
-  unsigned int random;
+#ifdef RANDOM_BUG
+  uint64_t random;
+#else
+  uint32_t random;
+#endif
 
   cave = lev.cave;
   next = lev.next;
@@ -7531,6 +7537,11 @@ static void logic_globals(void)
       Lamoeba(x, y);
 
     random = random * 129 + 1;
+
+#ifdef RANDOM_BUG
+    if (!game_em.use_random_bug)
+      random = (uint32_t)random;
+#endif
   }
 
   game_em.random = random;
diff --git a/src/tape.h b/src/tape.h
index c8c06759..d5a19ac8 100644
--- a/src/tape.h
+++ b/src/tape.h
@@ -37,6 +37,7 @@
 
 // values for tape properties stored in tape file
 #define TAPE_PROPERTY_NONE		0
+#define TAPE_PROPERTY_EM_RANDOM_BUG	(1 << 0)
 
 // some positions in the video tape control window
 #define VIDEO_DISPLAY1_XPOS	5