HybiDecode

gistfile1.cs

public string HybiDecode(byte[] data)
{
    byte firstByte = data[0];
    byte secondByte = data[1];
    int opcode = firstByte & 0x0F;
    bool isMasked = ((firstByte & 128) == 128);
    int payloadLength = secondByte & 0x7F;

    if (!isMasked) { return null; } // not masked
    if (opcode != 1) { return null; } // not text

    List<int> mask = new List<int>();
    for (int i = 2; i < 6; i++)
    {
        mask.Add(data[i]);
    }
    int payloadOffset = 6;
    int dataLength = payloadLength + payloadOffset;

    List<int> unmaskedPayload = new List<int>();
    for (int i = payloadOffset; i < dataLength; i++)
    {
        int j = i - payloadOffset;
        unmaskedPayload.Add(data[i] ^ mask[j % 4]);
    }

    return ToAscii(unmaskedPayload.Select(e => (byte)e).ToArray());
}

public string ToAscii(byte[] data)
{
    System.Text.ASCIIEncoding decoder = new System.Text.ASCIIEncoding();
    return decoder.GetString(data, 0, data.Length);
}