private static int GetPreambleLength(ArraySegment <byte> buffer, Encoding encoding)
{
byte[] array = buffer.Array;
int offset = buffer.Offset;
int count = buffer.Count;
switch (encoding.CodePage)
{
case 1200:
return(count < 2 || array[offset] != byte.MaxValue || array[offset + 1] != (byte)254 ? 0 : 2);
case 1201:
return(count < 2 || array[offset] != (byte)254 || array[offset + 1] != byte.MaxValue ? 0 : 2);
case 12000:
return(count < 4 || array[offset] != byte.MaxValue || (array[offset + 1] != (byte)254 || array[offset + 2] != (byte)0) || array[offset + 3] != (byte)0 ? 0 : 4);
case 65001:
return(count < 3 || array[offset] != (byte)239 || (array[offset + 1] != (byte)187 || array[offset + 2] != (byte)191) ? 0 : 3);
default:
byte[] preamble = encoding.GetPreamble();
return(!HttpContent.BufferHasPrefix(buffer, preamble) ? 0 : preamble.Length);
}
}
