Core classes Random & RandomStream port to C#

Source/Engine/Engine/RandomStream.cs

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+// Copyright (c) 2012-2022 Wojciech Figat. All rights reserved.
+
+using System;
+using System.Runtime.CompilerServices;
+
+#pragma warning disable 675
+
+namespace FlaxEngine
+{
+    /// <summary>
+    /// Very basic pseudo numbers generator.
+    /// </summary>
+    [HideInEditor]
+    public class RandomStream
+    {
+        /// <summary>
+        /// Holds the initial seed.
+        /// </summary>
+        private int _initialSeed = 0;
+        
+        /// <summary>
+        /// Holds the current seed.
+        /// </summary>
+        private int _seed = 0;
+
+        /// <summary>
+        /// Init
+        /// </summary>
+        public RandomStream()
+        {
+            _initialSeed = 0;
+            _seed = 0;
+        }
+
+        /// <summary>
+        /// Creates and initializes a new random stream from the specified seed value.
+        /// </summary>
+        /// <param name="seed">The seed value.</param>
+        public RandomStream(int seed)
+        {
+            _initialSeed = seed;
+            _seed = seed;
+        }
+
+        /// <summary>
+        /// Gets initial seed value
+        /// </summary>
+        public int GetInitialSeed()
+        {
+            return _initialSeed;
+        }
+
+
+        /// <summary>
+        /// Gets the current seed.
+        /// </summary>
+        public int GetCurrentSeed()
+        {
+            return _seed;
+        }
+
+        /// <summary>
+        /// Initializes this random stream with the specified seed value.
+        /// </summary>
+        /// <param name="seed">The seed value.</param>
+        public void Initialize(int seed)
+        {
+            _initialSeed = seed;
+            _seed = seed;
+        }
+
+        /// <summary>
+        /// Resets this random stream to the initial seed value.
+        /// </summary>
+        public void Reset()
+        {
+            _seed = _initialSeed;
+        }
+
+        /// <summary>
+        /// Generates a new random seed.
+        /// </summary>
+        public void GenerateNewSeed()
+        {
+            Initialize(new System.Random().Next());
+        }
+
+        /// <summary>
+        /// Returns a random boolean.
+        /// </summary>
+        public unsafe bool GetBool()
+        {
+            MutateSeed();
+            fixed (int* seedPtr= &_seed)
+            return *seedPtr < (uint.MaxValue/ 2);
+        }
+
+        /// <summary>
+        /// Returns a random number between 0 and uint.MaxValue.
+        /// </summary>
+        public unsafe uint GetUnsignedInt()
+        {
+            MutateSeed();
+            fixed (int* seedPtr = &_seed)
+            return (uint)*seedPtr;
+        }
+
+        /// <summary>
+        /// Returns a random number between 0 and 1.
+        /// </summary>
+        public unsafe float GetFraction()
+        {
+            MutateSeed();
+            float temp = 1.0f;
+            float result = 0.0f;
+            *(int*)&result = (int)((*(int*)&temp & 0xff800000) | (_seed & 0x007fffff));
+            return Mathf.Frac(result);
+        }
+
+        /// <summary>
+        /// Returns a random number between 0 and 1.
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public float Rand()
+        {
+            return GetFraction();
+        }
+
+        /// <summary>
+        /// Returns a random vector of unit size.
+        /// </summary>
+        public Float3 GetUnitVector()
+        {
+            Float3 result;
+            float l;
+            do
+            {
+                result.X = GetFraction() * 2.0f - 1.0f;
+                result.Y = GetFraction() * 2.0f - 1.0f;
+                result.Z = GetFraction() * 2.0f - 1.0f;
+                l = result.LengthSquared;
+            } while (l > 1.0f || l < Mathf.Epsilon);
+            return Float3.Normalize(result);
+        }
+
+        /// <summary>
+        /// Gets a random <see cref="Vector3"/> with components in a range between [0;1].
+        /// </summary>
+        public Vector3 GetVector3()
+        {
+            return new Vector3(GetFraction(), GetFraction(), GetFraction());
+        }
+
+        /// <summary>
+        /// Helper function for rand implementations.
+        /// </summary>
+        /// <param name="a">Top border</param>
+        /// <returns>A random number in [0..A)</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public int RandHelper(int a)
+        {
+            return a > 0 ? Mathf.FloorToInt(GetFraction() *((float)a - Mathf.Epsilon)) : 0;
+        }
+
+        /// <summary>
+        /// Helper function for rand implementations
+        /// </summary>
+        /// <param name="min">Minimum value</param>
+        /// <param name="max">Maximum value</param>
+        /// <returns>A random number in [min; max] range</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public int RandRange(int min, int max)
+        {
+            int range = max - min + 1;
+            return min + RandHelper(range);
+        }
+
+        /// <summary>
+        /// Helper function for rand implementations
+        /// </summary>
+        /// <param name="min">Minimum value</param>
+        /// <param name="max">Maximum value</param>
+        /// <returns>A random number in [min; max] range</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public float RandRange(float min, float max)
+        {
+            return min + (max - min) * Rand();
+        }
+    
+        /// <summary>
+        /// Mutates the current seed into the next seed.
+        /// </summary>
+        protected void MutateSeed()
+        {
+            // This can be modified to provide better randomization
+            _seed = _seed * 196314165 + 907633515;
+        }
+    }
+}

Source/Engine/Engine/RandomUtil.cs

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+// Copyright (c) 2012-2022 Wojciech Figat. All rights reserved.
+
+using System;
+using System.Runtime.CompilerServices;
+
+namespace FlaxEngine
+{
+    /// <summary>
+    /// Basic pseudo numbers generator utility.
+    /// </summary>
+    [HideInEditor]
+    public class RandomUtil
+    {
+        private static readonly Random _random = new Random();
+
+        /// <summary>
+        /// Generates a pseudo-random number from normalized range [0;1].
+        /// </summary>
+        /// <returns>The random number.</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static float Rand()
+        {
+            return _random.Next(0, int.MaxValue) / (float)int.MaxValue;
+        }
+    }
+}