RandomNumberGenerator.cs

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namespace System.Diagnostics;
 
internal sealed class RandomNumberGenerator
{
    [ThreadStatic]
    private static RandomNumberGenerator t_random;
 
    private ulong _s0;
 
    private ulong _s1;
 
    private ulong _s2;
 
    private ulong _s3;
 
    public static RandomNumberGenerator Current
    {
        get
        {
            if (t_random == null)
            {
                t_random = new RandomNumberGenerator();
            }
            return t_random;
        }
    }
 
    public unsafe RandomNumberGenerator()
    {
        do
        {
            Guid guid = Guid.NewGuid();
            Guid guid2 = Guid.NewGuid();
            ulong* ptr = (ulong*)(&guid);
            ulong* ptr2 = (ulong*)(&guid2);
            _s0 = *ptr;
            _s1 = ptr[1];
            _s2 = *ptr2;
            _s3 = ptr2[1];
            _s0 = (_s0 & 0xFFFFFFFFFFFFFFFuL) | (_s1 & 0xF000000000000000uL);
            _s2 = (_s2 & 0xFFFFFFFFFFFFFFFuL) | (_s3 & 0xF000000000000000uL);
            _s1 = (_s1 & 0xFFFFFFFFFFFFFF3FuL) | (_s0 & 0xC0);
            _s3 = (_s3 & 0xFFFFFFFFFFFFFF3FuL) | (_s2 & 0xC0);
        }
        while ((_s0 | _s1 | _s2 | _s3) == 0L);
    }
 
    private ulong Rol64(ulong x, int k)
    {
        return (x << k) | (x >> 64 - k);
    }
 
    public long Next()
    {
        ulong result = Rol64(_s1 * 5, 7) * 9;
        ulong num = _s1 << 17;
        _s2 ^= _s0;
        _s3 ^= _s1;
        _s1 ^= _s2;
        _s0 ^= _s3;
        _s2 ^= num;
        _s3 = Rol64(_s3, 45);
        return (long)result;
    }
}