IntegerEncoder.cs

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namespace System.Net.Http.HPack;
 
internal static class IntegerEncoder
{
    public static bool Encode(int value, int numBits, Span<byte> destination, out int bytesWritten)
    {
        if (destination.Length == 0)
        {
            bytesWritten = 0;
            return false;
        }
        destination[0] &= MaskHigh(8 - numBits);
        if (value < (1 << numBits) - 1)
        {
            destination[0] |= (byte)value;
            bytesWritten = 1;
            return true;
        }
        destination[0] |= (byte)((1 << numBits) - 1);
        if (1 == destination.Length)
        {
            bytesWritten = 0;
            return false;
        }
        value -= (1 << numBits) - 1;
        int num = 1;
        while (value >= 128)
        {
            destination[num++] = (byte)(value % 128 + 128);
            if (num >= destination.Length)
            {
                bytesWritten = 0;
                return false;
            }
            value /= 128;
        }
        destination[num++] = (byte)value;
        bytesWritten = num;
        return true;
    }
 
    private static byte MaskHigh(int n)
    {
        return (byte)(-128 >> n - 1);
    }
}