/// <summary>
/// Encodes a websocket frame into a byte buffer to be sent through the network
/// </summary>
/// <param name="frame">Websocket frame to send</param>
/// <param name="mask">Only client should mask the message</param>
/// <returns>The encoded byte buffer</returns>
public static byte[] EncodeFrame(WebSocketFrame frame, bool mask = false)
{
var buffer = frame.Data ?? new byte[0];
var length = 0;
byte[] result;
var index = 0;
var lenBuf = new byte[0];
if (buffer.Length <= 125)
{
length = (mask) ? buffer.Length + 128 : buffer.Length;
// op code + length + key + data
result = new byte[1 + 1 + buffer.Length + (mask ? 4 : 0)];
index = 2;
}
else if (buffer.Length >= 126 && buffer.Length <= ushort.MaxValue)
{
length = (mask) ? 126 + 128 : 126;
// op code + length + ushort length + key + data
lenBuf = BitConverter.GetBytes((ushort)buffer.Length);
if (BitConverter.IsLittleEndian)
{
lenBuf = lenBuf.Reverse().ToArray();
}
result = new byte[1 + 1 + 2 + buffer.Length + (mask ? 4 : 0)];
Array.Copy(lenBuf, 0, result, 2, lenBuf.Length);
result[2] = (byte)((buffer.Length >> 8) & 0xFF);
result[3] = (byte)(buffer.Length & 0xFF);
index = 4;
}
else
{
length = (mask) ? 127 + 128 : 127;
// op code + length + ulong length + key + data
result = new byte[1 + 1 + 8 + buffer.Length + (mask ? 4 : 0)];
lenBuf = BitConverter.GetBytes((ulong)buffer.Length);
if (BitConverter.IsLittleEndian)
{
lenBuf = lenBuf.Reverse().ToArray();
}
Array.Copy(lenBuf, 0, result, 2, lenBuf.Length);
index = 10;
}
result[0] = (byte)(128 + frame.Code);
result[1] = (byte)length;
var key = (mask) ? new byte[] { 1, 2, 3, 4 } : new byte[] { 0, 0, 0, 0 };
if (mask)
{
for (int i = 0; i < key.Length; i++)
{
result[index + i] = key[i];
}
index += 4;
}
for (int i = 0; i < buffer.Length; i++)
{
result[index + i] = (byte)(buffer[i] ^ key[i % 4]);
}
return(result);
}
