llListRandomize() wasn't very random

Signed-off-by: Diva Canto <diva@metaverseink.com>

2 files changed, 58 insertions, 6 deletions

diff --git a/OpenSim/Framework/Util.cs b/OpenSim/Framework/Util.cs
index 56a90b1..2d0b280 100644
--- a/OpenSim/Framework/Util.cs
+++ b/OpenSim/Framework/Util.cs
@@ -3036,4 +3036,55 @@ namespace OpenSim.Framework
             }
         }
     }
+
+    public class BetterRandom
+    {
+        private const int BufferSize = 1024;  // must be a multiple of 4
+        private byte[] RandomBuffer;
+        private int BufferOffset;
+        private RNGCryptoServiceProvider rng;
+        public BetterRandom()
+        {
+            RandomBuffer = new byte[BufferSize];
+            rng = new RNGCryptoServiceProvider();
+            BufferOffset = RandomBuffer.Length;
+        }
+        private void FillBuffer()
+        {
+            rng.GetBytes(RandomBuffer);
+            BufferOffset = 0;
+        }
+        public int Next()
+        {
+            if (BufferOffset >= RandomBuffer.Length)
+            {
+                FillBuffer();
+            }
+            int val = BitConverter.ToInt32(RandomBuffer, BufferOffset) & 0x7fffffff;
+            BufferOffset += sizeof(int);
+            return val;
+        }
+        public int Next(int maxValue)
+        {
+            return Next() % maxValue;
+        }
+        public int Next(int minValue, int maxValue)
+        {
+            if (maxValue < minValue)
+            {
+                throw new ArgumentOutOfRangeException("maxValue must be greater than or equal to minValue");
+            }
+            int range = maxValue - minValue;
+            return minValue + Next(range);
+        }
+        public double NextDouble()
+        {
+            int val = Next();
+            return (double)val / int.MaxValue;
+        }
+        public void GetBytes(byte[] buff)
+        {
+            rng.GetBytes(buff);
+        }
+    }
 }
diff --git a/OpenSim/Region/ScriptEngine/Shared/Api/Implementation/LSL_Api.cs b/OpenSim/Region/ScriptEngine/Shared/Api/Implementation/LSL_Api.cs
index c5e02a6..53c198e 100644
--- a/OpenSim/Region/ScriptEngine/Shared/Api/Implementation/LSL_Api.cs
+++ b/OpenSim/Region/ScriptEngine/Shared/Api/Implementation/LSL_Api.cs
@@ -5631,7 +5631,7 @@ namespace OpenSim.Region.ScriptEngine.Shared.Api
         public LSL_List llListRandomize(LSL_List src, int stride)
         {
             LSL_List result;
-            Random rand           = new Random();
+            BetterRandom rand = new BetterRandom();
 
             int   chunkk;
             int[] chunks;
@@ -5647,24 +5647,25 @@ namespace OpenSim.Region.ScriptEngine.Shared.Api
             // If not, then return the src list. This also
             // traps those cases where stride > length.
 
-            if (src.Length != stride && src.Length%stride == 0)
+            if (src.Length != stride && src.Length % stride == 0)
             {
                 chunkk = src.Length/stride;
 
                 chunks = new int[chunkk];
 
                 for (int i = 0; i < chunkk; i++)
+                {
                     chunks[i] = i;
+                }
 
                 // Knuth shuffle the chunkk index
-                for (int i = chunkk - 1; i >= 1; i--)
+                for (int i = chunkk - 1; i > 0; i--)
                 {
                     // Elect an unrandomized chunk to swap
                     int index = rand.Next(i + 1);
-                    int tmp;
 
                     // and swap position with first unrandomized chunk
-                    tmp = chunks[i];
+                    int tmp = chunks[i];
                     chunks[i] = chunks[index];
                     chunks[index] = tmp;
                 }
@@ -5677,7 +5678,7 @@ namespace OpenSim.Region.ScriptEngine.Shared.Api
                 {
                     for (int j = 0; j < stride; j++)
                     {
-                        result.Add(src.Data[chunks[i]*stride+j]);
+                        result.Add(src.Data[chunks[i] * stride + j]);
                     }
                 }
             }