From 1465102ba0abb5ed6524d2743ac7768e917721b2 Mon Sep 17 00:00:00 2001
From: Christoph Oelckers <coelckers@users.noreply.github.com>
Date: Wed, 31 May 2017 11:33:57 +0200
Subject: [PATCH] - added SetRandomSeed function for ZScript. This uses the
 same RNG syntax as the other random functions.

---
 src/namedef.h                     |  2 +
 src/scripting/backend/codegen.cpp | 85 +++++++++++++++++++++++++++++++
 src/scripting/backend/codegen.h   | 21 ++++++++
 3 files changed, 108 insertions(+)

diff --git a/src/namedef.h b/src/namedef.h
index db492c1b27..a22a5de5f0 100644
--- a/src/namedef.h
+++ b/src/namedef.h
@@ -334,6 +334,8 @@ xx(FRandom)
 xx(Random2)
 xx(RandomPick)
 xx(FRandomPick)
+xx(SetRandomSeed)
+xx(BuiltinRandomSeed)
 xx(GetClass)
 xx(GetParentClass)
 xx(GetClassName)
diff --git a/src/scripting/backend/codegen.cpp b/src/scripting/backend/codegen.cpp
index f088bc2430..0613b91bde 100644
--- a/src/scripting/backend/codegen.cpp
+++ b/src/scripting/backend/codegen.cpp
@@ -5906,6 +5906,82 @@ ExpEmit FxRandom2::Emit(VMFunctionBuilder *build)
 	return out;
 }
 
+//==========================================================================
+//
+//
+//
+//==========================================================================
+FxRandomSeed::FxRandomSeed(FRandom * r, FxExpression *s, const FScriptPosition &pos, bool nowarn)
+	: FxExpression(EFX_Random, pos)
+{
+	EmitTail = false;
+	seed = new FxIntCast(s, nowarn);
+	rng = r;
+	ValueType = TypeVoid;
+}
+
+//==========================================================================
+//
+//
+//
+//==========================================================================
+
+FxRandomSeed::~FxRandomSeed()
+{
+	SAFE_DELETE(seed);
+}
+
+//==========================================================================
+//
+//
+//
+//==========================================================================
+
+FxExpression *FxRandomSeed::Resolve(FCompileContext &ctx)
+{
+	CHECKRESOLVED();
+	RESOLVE(seed, ctx);
+	return this;
+};
+
+
+//==========================================================================
+//
+//
+//
+//==========================================================================
+
+int BuiltinRandomSeed(VMValue *param, TArray<VMValue> &defaultparam, int numparam, VMReturn *ret, int numret)
+{
+	PARAM_PROLOGUE;
+	PARAM_POINTER(rng, FRandom)
+	PARAM_INT(seed);
+	rng->Init(seed);
+	return 0;
+}
+
+ExpEmit FxRandomSeed::Emit(VMFunctionBuilder *build)
+{
+	// Call DecoRandom to generate a random number.
+	VMFunction *callfunc;
+	PSymbol *sym = FindBuiltinFunction(NAME_BuiltinRandomSeed, BuiltinRandomSeed);
+
+	assert(sym->IsKindOf(RUNTIME_CLASS(PSymbolVMFunction)));
+	assert(((PSymbolVMFunction *)sym)->Function != nullptr);
+	callfunc = ((PSymbolVMFunction *)sym)->Function;
+
+	if (build->FramePointer.Fixed) EmitTail = false;	// do not tail call if the stack is in use
+	int opcode = (EmitTail ? OP_TAIL_K : OP_CALL_K);
+
+	build->Emit(OP_PARAM, 0, REGT_POINTER | REGT_KONST, build->GetConstantAddress(rng));
+	EmitParameter(build, seed, ScriptPosition);
+	build->Emit(opcode, build->GetConstantAddress(callfunc), 2, 1);
+
+	ExpEmit call;
+	if (EmitTail) call.Final = true;
+	return call;
+}
+
 //==========================================================================
 //
 //
@@ -7537,6 +7613,7 @@ FxFunctionCall::FxFunctionCall(FName methodname, FName rngname, FArgumentList &a
 		case NAME_RandomPick:
 		case NAME_FRandomPick:
 		case NAME_Random2:
+		case NAME_SetRandomSeed:
 			RNG = FRandom::StaticFindRNG(rngname.GetChars());
 			break;
 
@@ -7790,6 +7867,14 @@ FxExpression *FxFunctionCall::Resolve(FCompileContext& ctx)
 		}
 		break;
 
+	case NAME_SetRandomSeed:
+		if (CheckArgSize(NAME_Random, ArgList, 1, 1, ScriptPosition))
+		{
+			func = new FxRandomSeed(RNG, ArgList[0], ScriptPosition, ctx.FromDecorate);
+			ArgList[0] = nullptr;
+		}
+		break;
+
 	case NAME_Random:
 		// allow calling Random without arguments to default to (0, 255)
 		if (ArgList.Size() == 0)
diff --git a/src/scripting/backend/codegen.h b/src/scripting/backend/codegen.h
index 004b1f2289..2121eff7a4 100644
--- a/src/scripting/backend/codegen.h
+++ b/src/scripting/backend/codegen.h
@@ -1321,6 +1321,27 @@ public:
 };
 
 
+//==========================================================================
+//
+//
+//
+//==========================================================================
+
+class FxRandomSeed : public FxExpression
+{
+protected:
+	bool EmitTail;
+	FRandom *rng;
+	FxExpression *seed;
+
+public:
+
+	FxRandomSeed(FRandom *, FxExpression *mi, const FScriptPosition &pos, bool nowarn);
+	~FxRandomSeed();
+	FxExpression *Resolve(FCompileContext&);
+	ExpEmit Emit(VMFunctionBuilder *build);
+};
+
 //==========================================================================
 //
 //	FxMemberBase