Sha1ForNonSecretPurposes.cs

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using System.Numerics;
 
namespace System;
 
internal struct Sha1ForNonSecretPurposes
{
    private long _length;
 
    private uint[] _w;
 
    private int _pos;
 
    public void Start()
    {
        if (_w == null)
        {
            _w = new uint[85];
        }
        _length = 0L;
        _pos = 0;
        _w[80] = 1732584193u;
        _w[81] = 4023233417u;
        _w[82] = 2562383102u;
        _w[83] = 271733878u;
        _w[84] = 3285377520u;
    }
 
    public void Append(byte input)
    {
        int num = _pos >> 2;
        _w[num] = (_w[num] << 8) | input;
        if (64 == ++_pos)
        {
            Drain();
        }
    }
 
    public void Append(ReadOnlySpan<byte> input)
    {
        ReadOnlySpan<byte> readOnlySpan = input;
        for (int i = 0; i < readOnlySpan.Length; i++)
        {
            byte input2 = readOnlySpan[i];
            Append(input2);
        }
    }
 
    public void Finish(Span<byte> output)
    {
        long num = _length + 8 * _pos;
        Append(128);
        while (_pos != 56)
        {
            Append(0);
        }
        Append((byte)(num >> 56));
        Append((byte)(num >> 48));
        Append((byte)(num >> 40));
        Append((byte)(num >> 32));
        Append((byte)(num >> 24));
        Append((byte)(num >> 16));
        Append((byte)(num >> 8));
        Append((byte)num);
        int num2 = ((output.Length < 20) ? output.Length : 20);
        for (int i = 0; i != num2; i++)
        {
            uint num3 = _w[80 + i / 4];
            output[i] = (byte)(num3 >> 24);
            _w[80 + i / 4] = num3 << 8;
        }
    }
 
    private void Drain()
    {
        for (int i = 16; i != 80; i++)
        {
            _w[i] = BitOperations.RotateLeft(_w[i - 3] ^ _w[i - 8] ^ _w[i - 14] ^ _w[i - 16], 1);
        }
        uint num = _w[80];
        uint num2 = _w[81];
        uint num3 = _w[82];
        uint num4 = _w[83];
        uint num5 = _w[84];
        for (int j = 0; j != 20; j++)
        {
            uint num6 = (num2 & num3) | (~num2 & num4);
            uint num7 = BitOperations.RotateLeft(num, 5) + num6 + num5 + 1518500249 + _w[j];
            num5 = num4;
            num4 = num3;
            num3 = BitOperations.RotateLeft(num2, 30);
            num2 = num;
            num = num7;
        }
        for (int k = 20; k != 40; k++)
        {
            uint num8 = num2 ^ num3 ^ num4;
            uint num9 = BitOperations.RotateLeft(num, 5) + num8 + num5 + 1859775393 + _w[k];
            num5 = num4;
            num4 = num3;
            num3 = BitOperations.RotateLeft(num2, 30);
            num2 = num;
            num = num9;
        }
        for (int l = 40; l != 60; l++)
        {
            uint num10 = (num2 & num3) | (num2 & num4) | (num3 & num4);
            uint num11 = (uint)((int)(BitOperations.RotateLeft(num, 5) + num10 + num5) + -1894007588) + _w[l];
            num5 = num4;
            num4 = num3;
            num3 = BitOperations.RotateLeft(num2, 30);
            num2 = num;
            num = num11;
        }
        for (int m = 60; m != 80; m++)
        {
            uint num12 = num2 ^ num3 ^ num4;
            uint num13 = (uint)((int)(BitOperations.RotateLeft(num, 5) + num12 + num5) + -899497514) + _w[m];
            num5 = num4;
            num4 = num3;
            num3 = BitOperations.RotateLeft(num2, 30);
            num2 = num;
            num = num13;
        }
        _w[80] += num;
        _w[81] += num2;
        _w[82] += num3;
        _w[83] += num4;
        _w[84] += num5;
        _length += 512L;
        _pos = 0;
    }
}