/// <summary>
/// Creates an instance of a WebSocketPayloadReader.
/// </summary>
/// <param name="header">The WebSocketHeader associated with this payload.</param>
public WebSocketPayloadReader(WebSocketHeader header)
{
_payloadBytesRemaining = header.PayloadLength;
_payloadEncoder = new WebSocketPayloadEncoder(header.MaskingKey);
_masked = header.Masked;
}
/// <summary>
/// Writes the WebSocketWriteFrame to the provided buffer writer.
/// </summary>
/// <param name="message">The message to write.</param>
/// <param name="output">The buffer writer to write the message to.</param>
public unsafe void WriteMessage(WebSocketWriteFrame message, IBufferWriter <byte> output)
{
if (message.Header.PayloadLength != (ulong)message.Payload.Length)
{
throw new WebSocketFrameException($"Header payload length ({message.Header.PayloadLength}) does not equal supplied payload length ({message.Payload.Length})");
}
var headerSize = 2;
var extendedPayloadLengthSize = 0;
var maskPosition = 2;
if (message.Header.PayloadLength > 125)
{
if (message.Header.PayloadLength <= ushort.MaxValue)
{
extendedPayloadLengthSize = 2;
maskPosition += 2;
}
else
{
extendedPayloadLengthSize = 8;
maskPosition += 8;
}
}
if (message.Header.Masked)
{
headerSize += extendedPayloadLengthSize + 4;
}
else
{
headerSize += extendedPayloadLengthSize;
}
Span <byte> headerSpan = (stackalloc byte[14]).Slice(0, headerSize);
headerSpan[0] = (byte)message.Header.Opcode;
if (message.Header.Fin)
{
headerSpan[0] |= 0b1000_0000;
}
switch (extendedPayloadLengthSize)
{
case 2:
headerSpan[1] = 126;
BinaryPrimitives.WriteUInt16BigEndian(headerSpan.Slice(2), (ushort)message.Header.PayloadLength);
break;
case 8:
headerSpan[1] = 127;
BinaryPrimitives.WriteUInt64BigEndian(headerSpan.Slice(2), message.Header.PayloadLength);
break;
default:
headerSpan[1] = (byte)message.Header.PayloadLength;
break;
}
if (message.Header.Masked)
{
headerSpan[1] |= 0b1000_0000;
var maskingKey = message.Header.MaskingKey;
MemoryMarshal.Write(headerSpan.Slice(maskPosition), ref maskingKey);
if (!message.MaskingComplete)
{
var encoder = new WebSocketPayloadEncoder(message.Header.MaskingKey);
encoder.MaskUnmaskPayload(message.Payload, message.Header.PayloadLength, out var _);
message.MaskingComplete = true;
}
}
output.Write(headerSpan);
if (message.Payload.IsSingleSegment)
{
output.Write(message.Payload.FirstSpan);
}
else
{
foreach (var memory in message.Payload)
{
output.Write(memory.Span);
}
}
}