- Now base the old PRNG flag on Edward850's implementation but done in reverse.

Also disable it for some generators.
https://forum.zdoom.org/viewtopic.php?f=4&t=47546

src/fragglescript/t_func.cpp

@@ -63,7 +63,7 @@
 #include "vm.h"
 #include "s_music.h"
 
-static FRandom pr_script("FScript");
+static FRandom pr_script("FScript", false);
 
 // functions. FParser::SF_ means Script Function not, well.. heh, me
 

src/m_random.cpp

@@ -171,7 +171,7 @@ static TDeletingArray<FRandom *> NewRNGs;
 // CODE --------------------------------------------------------------------
 
 // Which one is deterministic?
-int P_Random (void)
+unsigned int P_Random (void)
 {
 	prndindex = (prndindex+1)&0xff;
 	return rndtable[prndindex];
@@ -191,7 +191,7 @@ void M_ClearRandom (void)
 //==========================================================================
 
 FRandom::FRandom ()
-: NameCRC (0)
+: NameCRC (0), useOldRNG (false)
 {
 #ifndef NDEBUG
 	Name = NULL;
@@ -210,9 +210,10 @@ FRandom::FRandom ()
 //
 //==========================================================================
 
-FRandom::FRandom (const char *name)
+FRandom::FRandom (const char *name, bool useold)
 {
 	NameCRC = CalcCRC32 ((const uint8_t *)name, (unsigned int)strlen (name));
+	useOldRNG = useold;
 #ifndef NDEBUG
 	initialized = false;
 	Name = name;
@@ -273,6 +274,21 @@ FRandom::~FRandom ()
 	}
 }
 
+//==========================================================================
+//
+// FRandom::GetRandom()
+//
+// Returns either an old PRNG value or an SFMT value
+//
+//==========================================================================
+
+unsigned int FRandom::GetRandom()
+{
+	if (useOldRNG && (compatflags2 & COMPATF2_OLD_RANDOM_GENERATOR))
+		return P_Random();
+	else return GenRand32();
+}
+
 //==========================================================================
 //
 // FRandom :: StaticClearRandom
@@ -325,7 +341,8 @@ uint32_t FRandom::StaticSumSeeds ()
 		pr_spawnmobj.sfmt.u[0] + pr_spawnmobj.idx +
 		pr_acs.sfmt.u[0] + pr_acs.idx +
 		pr_chase.sfmt.u[0] + pr_chase.idx +
-		pr_damagemobj.sfmt.u[0] + pr_damagemobj.idx;
+		pr_damagemobj.sfmt.u[0] + pr_damagemobj.idx +
+		prndindex;
 }
 
 //==========================================================================

src/m_random.h

@@ -45,13 +45,15 @@ class FRandom
 {
 public:
 	FRandom ();
-	FRandom (const char *name);
+	FRandom (const char *name, bool useold = true);
 	~FRandom ();
 
+	unsigned int GetRandom(); // [ED850]
+
 	// Returns a random number in the range [0,255]
 	int operator()()
 	{
-		return GenRand32() & 255;
+		return GetRandom() & 255;
 	}
 
 	// Returns a random number in the range [0,mod)
@@ -59,7 +61,7 @@ public:
 	{
 		return (0 == mod)
 			? 0
-			: (GenRand32() % mod);
+			: (GetRandom() % mod);
 	}
 
 	// Returns rand# - rand#
@@ -71,8 +73,8 @@ public:
 // Returns (rand# & mask) - (rand# & mask)
 	int Random2(int mask)
 	{
-		int t = GenRand32() & mask & 255;
-		return t - (GenRand32() & mask & 255);
+		int t = GetRandom() & mask & 255;
+		return t - (GetRandom() & mask & 255);
 	}
 
 	// HITDICE macro used in Heretic and Hexen
@@ -213,6 +215,9 @@ private:
 #ifndef NDEBUG
 	bool initialized;
 #endif
+
+	// Use the old PRNG table if/when requested [ED850]
+	bool useOldRNG;
 };
 
 extern uint32_t rngseed;			// The starting seed (not part of state)
@@ -225,7 +230,7 @@ extern bool use_staticrng;
 extern FRandom M_Random;
 
 // Returns a number from 0 to 255, from a lookup table.
-int P_Random (void);
+unsigned int P_Random (void);
 void M_ClearRandom (void);
 
 extern int prndindex;

src/p_acs.cpp

@@ -543,7 +543,7 @@
 
 extern FILE *Logfile;
 
-FRandom pr_acs ("ACS");
+FRandom pr_acs ("ACS", false);
 
 // I imagine this much stack space is probably overkill, but it could
 // potentially get used with recursive functions.

src/p_actionfunctions.cpp

@@ -88,19 +88,19 @@
 AActor *SingleActorFromTID(int tid, AActor *defactor);
 
 
-static FRandom pr_camissile ("CustomActorfire");
-static FRandom pr_cabullet ("CustomBullet");
-static FRandom pr_cwjump ("CustomWpJump");
-static FRandom pr_cwpunch ("CustomWpPunch");
+static FRandom pr_camissile ("CustomActorfire", false);
+static FRandom pr_cabullet ("CustomBullet", false);
+static FRandom pr_cwjump ("CustomWpJump", false);
+static FRandom pr_cwpunch ("CustomWpPunch", false);
 static FRandom pr_grenade ("ThrowGrenade");
-static FRandom pr_crailgun ("CustomRailgun");
-static FRandom pr_spawndebris ("SpawnDebris");
-static FRandom pr_spawnitemex ("SpawnItemEx");
-static FRandom pr_burst ("Burst");
+static FRandom pr_crailgun ("CustomRailgun", false);
+static FRandom pr_spawndebris ("SpawnDebris", false);
+static FRandom pr_spawnitemex ("SpawnItemEx", false);
+static FRandom pr_burst ("Burst", false);
 static FRandom pr_monsterrefire ("MonsterRefire");
 static FRandom pr_teleport("A_Teleport");
 static FRandom pr_bfgselfdamage("BFGSelfDamage");
-FRandom pr_cajump("CustomJump");
+FRandom pr_cajump("CustomJump", false);
 
 //==========================================================================
 //

src/scripting/decorate/thingdef_exp.cpp

@@ -51,7 +51,7 @@
 #include "doomstat.h"
 #include "backend/codegen.h"
 
-FRandom pr_exrandom ("EX_Random");
+FRandom pr_exrandom ("EX_Random", false);
 
 static FxExpression *ParseRandom(FScanner &sc, FName identifier, PClassActor *cls);
 static FxExpression *ParseRandomPick(FScanner &sc, FName identifier, PClassActor *cls);