IntegerDecoder.cs

Go to the documentation of this file.

using System.Numerics;
 
namespace System.Net.Http.HPack;
 
internal struct IntegerDecoder
{
    private int _i;
 
    private int _m;
 
    public bool BeginTryDecode(byte b, int prefixLength, out int result)
    {
        if (b < (1 << prefixLength) - 1)
        {
            result = b;
            return true;
        }
        _i = b;
        _m = 0;
        result = 0;
        return false;
    }
 
    public bool TryDecode(byte b, out int result)
    {
        if (BitOperations.LeadingZeroCount(b) <= _m)
        {
            throw new HPackDecodingException(System.SR.net_http_hpack_bad_integer);
        }
        _i += (b & 0x7F) << _m;
        if (_i < 0)
        {
            throw new HPackDecodingException(System.SR.net_http_hpack_bad_integer);
        }
        _m += 7;
        if ((b & 0x80) == 0)
        {
            if (b == 0 && _m / 7 > 1)
            {
                throw new HPackDecodingException(System.SR.net_http_hpack_bad_integer);
            }
            result = _i;
            return true;
        }
        result = 0;
        return false;
    }
}