NumericsHelpers.cs

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using System.Runtime.CompilerServices;
 
namespace System.Numerics;
 
internal static class NumericsHelpers
{
    public static void GetDoubleParts(double dbl, out int sign, out int exp, out ulong man, out bool fFinite)
    {
        Unsafe.SkipInit(out DoubleUlong doubleUlong);
        doubleUlong.uu = 0uL;
        doubleUlong.dbl = dbl;
        sign = 1 - ((int)(doubleUlong.uu >> 62) & 2);
        man = doubleUlong.uu & 0xFFFFFFFFFFFFFuL;
        exp = (int)(doubleUlong.uu >> 52) & 0x7FF;
        if (exp == 0)
        {
            fFinite = true;
            if (man != 0L)
            {
                exp = -1074;
            }
        }
        else if (exp == 2047)
        {
            fFinite = false;
            exp = int.MaxValue;
        }
        else
        {
            fFinite = true;
            man |= 4503599627370496uL;
            exp -= 1075;
        }
    }
 
    public static double GetDoubleFromParts(int sign, int exp, ulong man)
    {
        Unsafe.SkipInit(out DoubleUlong doubleUlong);
        doubleUlong.dbl = 0.0;
        if (man == 0L)
        {
            doubleUlong.uu = 0uL;
        }
        else
        {
            int num = CbitHighZero(man) - 11;
            man = ((num >= 0) ? (man << num) : (man >> -num));
            exp -= num;
            exp += 1075;
            if (exp >= 2047)
            {
                doubleUlong.uu = 9218868437227405312uL;
            }
            else if (exp <= 0)
            {
                exp--;
                if (exp < -52)
                {
                    doubleUlong.uu = 0uL;
                }
                else
                {
                    doubleUlong.uu = man >> -exp;
                }
            }
            else
            {
                doubleUlong.uu = (man & 0xFFFFFFFFFFFFFuL) | (ulong)((long)exp << 52);
            }
        }
        if (sign < 0)
        {
            doubleUlong.uu |= 9223372036854775808uL;
        }
        return doubleUlong.dbl;
    }
 
    public static void DangerousMakeTwosComplement(Span<uint> d)
    {
        if (d != null && d.Length > 0)
        {
            d[0] = ~d[0] + 1;
            int i;
            for (i = 1; d[i - 1] == 0 && i < d.Length; i++)
            {
                d[i] = ~d[i] + 1;
            }
            for (; i < d.Length; i++)
            {
                d[i] = ~d[i];
            }
        }
    }
 
    public static ulong MakeUlong(uint uHi, uint uLo)
    {
        return ((ulong)uHi << 32) | uLo;
    }
 
    public static uint Abs(int a)
    {
        uint num = (uint)(a >> 31);
        return ((uint)a ^ num) - num;
    }
 
    public static uint CombineHash(uint u1, uint u2)
    {
        return ((u1 << 7) | (u1 >> 25)) ^ u2;
    }
 
    public static int CombineHash(int n1, int n2)
    {
        return (int)CombineHash((uint)n1, (uint)n2);
    }
 
    public static int CbitHighZero(uint u)
    {
        if (u == 0)
        {
            return 32;
        }
        int num = 0;
        if ((u & 0xFFFF0000u) == 0)
        {
            num += 16;
            u <<= 16;
        }
        if ((u & 0xFF000000u) == 0)
        {
            num += 8;
            u <<= 8;
        }
        if ((u & 0xF0000000u) == 0)
        {
            num += 4;
            u <<= 4;
        }
        if ((u & 0xC0000000u) == 0)
        {
            num += 2;
            u <<= 2;
        }
        if ((u & 0x80000000u) == 0)
        {
            num++;
        }
        return num;
    }
 
    public static int CbitHighZero(ulong uu)
    {
        if ((uu & 0xFFFFFFFF00000000uL) == 0L)
        {
            return 32 + CbitHighZero((uint)uu);
        }
        return CbitHighZero((uint)(uu >> 32));
    }
}