JitterCacheRng.cs

using System;
using System.Security.Cryptography;
using System.Threading;
[Serializable]
public class JitterCacheRng : RandomNumberGenerator
{
    private const    int        ReSecureThreshold = 10;
    private readonly SHA3ModInt _algorithm;
    private readonly JitterEx   _jit;
    private readonly int        _moveSize;
    private          int        _availableCacheBytes;
    private          byte[]     _cache;
    private          byte[]     _cacheBuffer;
    private          int        _cacheSize;
    private          int        _ptr;
    public           int        cacheFills;
    public JitterCacheRng() : this(1048576, 256, 256, 4)
    {
    }
    public JitterCacheRng(int cacheSize) : this(cacheSize, 256, 256, 4)
    {
    }
    public JitterCacheRng(int cacheSize, int seedSize) : this(cacheSize, seedSize, 256, 4)
    {
    }
    public JitterCacheRng(int cacheSize, int seedSize, int sha3Size) : this(cacheSize, seedSize, sha3Size, 4)
    {
    }
    public JitterCacheRng(int cacheSize, int seedSize, int sha3Size, int sha3Rounds)
    {
        if (cacheSize == 0)
            throw new ArgumentException("Cache Size cannot be zero");
        if (seedSize < 256)
            throw new ArgumentException("The seed size should be 256 or more bytes.");
        if (sha3Size < 64 && sha3Size % 64 != 0)
            throw new ArgumentException("The bitWidth of the SHA3 hash algorithm need to be at least 64 bits and a multiple of 64.");
        if (sha3Rounds < 4)
            throw new ArgumentException("Sha3 rounds of less than 4 might produce some short run repetitive sequences.");
        _cacheSize   = cacheSize;
        _jit         = new JitterEx(seedSize);
        _cacheBuffer = _jit.GetBuffer();
        _cache       = new byte[_cacheSize];
        _algorithm   = new SHA3ModInt(sha3Size, sha3Rounds);
        _moveSize    = _algorithm.ComputeHash(2.GetBytes()).Length;
        FillCache();
    }
    public bool Protect
    {
        get;
        set;
    }
    protected override void Dispose(bool disposing)
    {
        _cache.Fill(0);
        _availableCacheBytes = 0;
        _algorithm.Dispose();
    }
    public override void GetBytes(byte[] data)
    {
        if (data.Length > _cacheSize)
        {
            _cacheSize = data.Length;
            _cache     = new byte[_cacheSize];
            FillCache();
        }
        if (_availableCacheBytes == 0 || _availableCacheBytes < data.Length)
        {
            if (_cacheSize < data.Length)
            {
                _cacheSize = data.Length;
                _cache     = new byte[_cacheSize];
            }
            FillCache();
        }
        if (_ptr + data.Length > _cacheSize)
            FillCache();
        if (Protect)
            ProtectedMemory.Unprotect(_cache, MemoryProtectionScope.SameLogon);
        Buffer.BlockCopy(_cache, _ptr, data, 0, data.Length);
        if (Protect)
            ProtectedMemory.Protect(_cache, MemoryProtectionScope.SameLogon);
        _ptr                 += data.Length;
        _availableCacheBytes -= data.Length;
    }
    private void FillCache()
    {
        var btrd = new Thread(() =>
        {
            _availableCacheBytes = 0;
            _ptr                 = 0;
            var p        = 0;
            var moveSize = _moveSize;
            cacheFills++;
            if (cacheFills % ReSecureThreshold == 0)
                _cacheBuffer = _jit.GetBuffer();
            if (Protect)
                ProtectedMemory.Unprotect(_cache, MemoryProtectionScope.SameLogon);
            while (true)
            {
                var remainingBytesToMove = _cacheSize - _availableCacheBytes;
                if (remainingBytesToMove < moveSize)
                    moveSize = remainingBytesToMove;
                if (remainingBytesToMove <= 0)
                    break;
                _cacheBuffer = _algorithm.ComputeHash(_cacheBuffer);
                Buffer.BlockCopy(_cacheBuffer, 0, _cache, p, moveSize);
                p                    += moveSize;
                _availableCacheBytes += moveSize;
            }
            if (Protect)
                ProtectedMemory.Protect(_cache, MemoryProtectionScope.SameLogon);
        }) {Priority = ThreadPriority.Highest};
        btrd.Start();
        btrd.Join();
    }
}

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