From df41a3a7dfe7f3bc69eabef3a4afe0e9f2a8d8e1 Mon Sep 17 00:00:00 2001
From: Nat Goodspeed <nat@lindenlab.com>
Date: Thu, 17 Aug 2023 09:14:54 -0400
Subject: DRTVWR-588: Finally ditch LL_USE_SYSTEM_RAND code in llrand.cpp.

This conditional code hasn't been used since June 2008, possibly even earlier.
---
 indra/llcommon/llrand.cpp | 104 +++++++++++++++++-----------------------------
 1 file changed, 39 insertions(+), 65 deletions(-)

(limited to 'indra')

diff --git a/indra/llcommon/llrand.cpp b/indra/llcommon/llrand.cpp
index cb28a8f5c3..33afc50cf7 100644
--- a/indra/llcommon/llrand.cpp
+++ b/indra/llcommon/llrand.cpp
@@ -58,46 +58,14 @@
  * to restore uniform distribution.
  */
 
-// *NOTE: The system rand implementation is probably not correct.
-#define LL_USE_SYSTEM_RAND 0
+static LLRandLagFib2281 gRandomGenerator(LLUUID::getRandomSeed());
 
-#if LL_USE_SYSTEM_RAND
-#include <cstdlib>
-#endif
+// no default implementation, only specific F64 and F32 specializations
+template <typename REAL>
+inline REAL ll_internal_random();
 
-#if LL_USE_SYSTEM_RAND
-class LLSeedRand
-{
-public:
-	LLSeedRand()
-	{
-#if LL_WINDOWS
-		srand(LLUUID::getRandomSeed());
-#else
-		srand48(LLUUID::getRandomSeed());
-#endif
-	}
-};
-static LLSeedRand sRandomSeeder;
-inline F64 ll_internal_random_double()
-{
-#if LL_WINDOWS
-	return (F64)rand() / (F64)RAND_MAX; 
-#else
-	return drand48();
-#endif
-}
-inline F32 ll_internal_random_float()
-{
-#if LL_WINDOWS
-	return (F32)rand() / (F32)RAND_MAX; 
-#else
-	return (F32)drand48();
-#endif
-}
-#else
-static LLRandLagFib2281 gRandomGenerator(LLUUID::getRandomSeed());
-inline F64 ll_internal_random_double()
+template <>
+inline F64 ll_internal_random<F64>()
 {
 	// *HACK: Through experimentation, we have found that dual core
 	// CPUs (or at least multi-threaded processes) seem to
@@ -108,15 +76,35 @@ inline F64 ll_internal_random_double()
 	return rv;
 }
 
+template <>
+inline F32 ll_internal_random<F32>()
+{
+    return F32(ll_internal_random<F64>());
+}
+
+/*------------------------------ F64 aliases -------------------------------*/
+inline F64 ll_internal_random_double()
+{
+    return ll_internal_random<F64>();
+}
+
+F64 ll_drand()
+{
+	return ll_internal_random_double();
+}
+
+/*------------------------------ F32 aliases -------------------------------*/
 inline F32 ll_internal_random_float()
 {
-	// The clamping rules are described above.
-	F32 rv = (F32)gRandomGenerator();
-	if(!((rv >= 0.0f) && (rv < 1.0f))) return fmod(rv, 1.f);
-	return rv;
+    return ll_internal_random<F32>();
+}
+
+F32 ll_frand()
+{
+	return ll_internal_random_float();
 }
-#endif
 
+/*-------------------------- clamped random range --------------------------*/
 S32 ll_rand()
 {
 	return ll_rand(RAND_MAX);
@@ -130,42 +118,28 @@ S32 ll_rand(S32 val)
 	return rv;
 }
 
-F32 ll_frand()
-{
-	return ll_internal_random_float();
-}
-
-F32 ll_frand(F32 val)
+template <typename REAL>
+REAL ll_grand(REAL val)
 {
 	// The clamping rules are described above.
-	F32 rv = ll_internal_random_float() * val;
+	REAL rv = ll_internal_random<REAL>() * val;
 	if(val > 0)
 	{
-		if(rv >= val) return 0.0f;
+		if(rv >= val) return REAL();
 	}
 	else
 	{
-		if(rv <= val) return 0.0f;
+		if(rv <= val) return REAL();
 	}
 	return rv;
 }
 
-F64 ll_drand()
+F32 ll_frand(F32 val)
 {
-	return ll_internal_random_double();
+    return ll_grand<F32>(val);
 }
 
 F64 ll_drand(F64 val)
 {
-	// The clamping rules are described above.
-	F64 rv = ll_internal_random_double() * val;
-	if(val > 0)
-	{
-		if(rv >= val) return 0.0;
-	}
-	else
-	{
-		if(rv <= val) return 0.0;
-	}
-	return rv;
+    return ll_grand<F64>(val);
 }
-- 
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