WIP

Esiur/Net/Ppap/RandomGenerator.cs

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+using Org.BouncyCastle.Crypto;
+using Org.BouncyCastle.Crypto.Prng;
+using Org.BouncyCastle.Security;
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace Esiur.Net.Ppap
+{
+    public class RandomGenerator
+         : SecureRandom
+    {
+        private static long counter = DateTime.UtcNow.Ticks;
+
+        private static long NextCounterValue()
+        {
+            return Interlocked.Increment(ref counter);
+        }
+
+        private static readonly SecureRandom MasterRandom = new SecureRandom(new CryptoApiRandomGenerator());
+        internal static readonly SecureRandom ArbitraryRandom = new SecureRandom(new VmpcRandomGenerator(), 16);
+
+        private static DigestRandomGenerator CreatePrng(string digestName, bool autoSeed)
+        {
+            IDigest digest = DigestUtilities.GetDigest(digestName);
+            if (digest == null)
+                return null;
+            DigestRandomGenerator prng = new DigestRandomGenerator(digest);
+            if (autoSeed)
+            {
+                AutoSeed(prng, 2 * digest.GetDigestSize());
+            }
+            return prng;
+        }
+
+        public static new byte[] GetNextBytes(SecureRandom secureRandom, int length)
+        {
+            byte[] result = new byte[length];
+            secureRandom.NextBytes(result);
+            return result;
+        }
+
+        public static new SecureRandom GetInstance(string algorithm)
+        {
+            return GetInstance(algorithm, true);
+        }
+
+        public static new SecureRandom GetInstance(string algorithm, bool autoSeed)
+        {
+            if (algorithm == null)
+                throw new ArgumentNullException(nameof(algorithm));
+
+            if (algorithm.EndsWith("PRNG", StringComparison.OrdinalIgnoreCase))
+            {
+                string digestName = algorithm.Substring(0, algorithm.Length - "PRNG".Length);
+
+                DigestRandomGenerator prng = CreatePrng(digestName, autoSeed);
+                if (prng != null)
+                    return new SecureRandom(prng);
+            }
+
+            throw new ArgumentException("Unrecognised PRNG algorithm: " + algorithm, "algorithm");
+        }
+
+        protected new readonly IRandomGenerator generator;
+
+        public RandomGenerator()
+            : this(CreatePrng("SHA256", true))
+        {
+
+        }
+
+        public RandomGenerator(IRandomGenerator generator)
+
+        {
+            this.generator = generator;
+        }
+
+        public RandomGenerator(IRandomGenerator generator, int autoSeedLengthInBytes)
+
+        {
+            AutoSeed(generator, autoSeedLengthInBytes);
+
+            this.generator = generator;
+        }
+
+        public override byte[] GenerateSeed(int length)
+        {
+            return GetNextBytes(MasterRandom, length);
+        }
+
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public override void GenerateSeed(Span<byte> seed)
+        {
+            MasterRandom.NextBytes(seed);
+        }
+#endif
+
+        public override void SetSeed(byte[] seed)
+        {
+            generator.AddSeedMaterial(seed);
+        }
+
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public override void SetSeed(Span<byte> seed)
+        {
+            generator.AddSeedMaterial(seed);
+        }
+#endif
+
+        public override void SetSeed(long seed)
+        {
+            generator.AddSeedMaterial(seed);
+        }
+
+        public override int Next()
+        {
+            return NextInt() & int.MaxValue;
+        }
+
+        public override int Next(int maxValue)
+        {
+            if (maxValue < 2)
+            {
+                if (maxValue < 0)
+                    throw new ArgumentOutOfRangeException("maxValue", "cannot be negative");
+
+                return 0;
+            }
+
+            int bits;
+
+            // Test whether maxValue is a power of 2
+            if ((maxValue & (maxValue - 1)) == 0)
+            {
+                bits = NextInt() & int.MaxValue;
+                return (int)(((long)bits * maxValue) >> 31);
+            }
+
+            int result;
+            do
+            {
+                bits = NextInt() & int.MaxValue;
+                result = bits % maxValue;
+            }
+            while (bits - result + (maxValue - 1) < 0); // Ignore results near overflow
+
+            return result;
+        }
+
+        public override int Next(int minValue, int maxValue)
+        {
+            if (maxValue <= minValue)
+            {
+                if (maxValue == minValue)
+                    return minValue;
+
+                throw new ArgumentException("maxValue cannot be less than minValue");
+            }
+
+            int diff = maxValue - minValue;
+            if (diff > 0)
+                return minValue + Next(diff);
+
+            for (; ; )
+            {
+                int i = NextInt();
+
+                if (i >= minValue && i < maxValue)
+                    return i;
+            }
+        }
+
+        public override void NextBytes(byte[] buf)
+        {
+            generator.NextBytes(buf);
+        }
+
+        public override void NextBytes(byte[] buf, int off, int len)
+        {
+            generator.NextBytes(buf, off, len);
+        }
+
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public override void NextBytes(Span<byte> buffer)
+        {
+            if (generator != null)
+            {
+                generator.NextBytes(buffer);
+            }
+            else
+            {
+                byte[] tmp = new byte[buffer.Length];
+                NextBytes(tmp);
+                tmp.CopyTo(buffer);
+            }
+        }
+#endif
+
+        private static readonly double DoubleScale = 1.0 / Convert.ToDouble(1L << 53);
+
+        public override double NextDouble()
+        {
+            ulong x = (ulong)NextLong() >> 11;
+
+            return Convert.ToDouble(x) * DoubleScale;
+        }
+
+        public override int NextInt()
+        {
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+            Span<byte> bytes = stackalloc byte[4];
+#else
+            byte[] bytes = new byte[4];
+#endif
+            NextBytes(bytes);
+            return (int)0;
+        }
+
+        public override long NextLong()
+        {
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+            Span<byte> bytes = stackalloc byte[8];
+#else
+            byte[] bytes = new byte[8];
+#endif
+            NextBytes(bytes);
+            return (long)0;
+        }
+
+        private static void AutoSeed(IRandomGenerator generator, int seedLength)
+        {
+            generator.AddSeedMaterial(NextCounterValue());
+
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+            Span<byte> seed = seedLength <= 128
+                ? stackalloc byte[seedLength]
+                : new byte[seedLength];
+#else
+            byte[] seed = new byte[seedLength];
+#endif
+            MasterRandom.NextBytes(seed);
+            generator.AddSeedMaterial(seed);
+        }
+    }
+
+}