Method writeFrame

write.go:288–373

writeFrame handles all writes to the connection.

(ctx context.Context, fin bool, flate bool, opcode opcode, p []byte)

// writeFrame handles all writes to the connection.
func (c *Conn) writeFrame(ctx context.Context, fin bool, flate bool, opcode opcode, p []byte) (_ int, err error) {
	err = c.writeFrameMu.lock(ctx)
	if err != nil {
		return 0, err
	}
	defer c.writeFrameMu.unlock()

	defer func() {
		if c.isClosed() && opcode == opClose {
			err = nil
		}
		if err != nil {
			if ctx.Err() != nil {
				err = ctx.Err()
			} else if c.isClosed() {
				err = net.ErrClosed
			}
			err = fmt.Errorf("failed to write frame: %w", err)
		}
	}()

	c.closeStateMu.Lock()
	closeSentErr := c.closeSentErr
	c.closeStateMu.Unlock()
	if closeSentErr != nil {
		return 0, net.ErrClosed
	}

	select {
	case <-c.closed:
		return 0, net.ErrClosed
	default:
	}
	if c.setupWriteTimeout(ctx) {
		defer c.clearWriteTimeout()
	}

	c.writeHeader.fin = fin
	c.writeHeader.opcode = opcode
	c.writeHeader.payloadLength = int64(len(p))

	if c.client {
		c.writeHeader.masked = true
		_, err = io.ReadFull(rand.Reader, c.writeHeaderBuf[:4])
		if err != nil {
			return 0, fmt.Errorf("failed to generate masking key: %w", err)
		}
		c.writeHeader.maskKey = binary.LittleEndian.Uint32(c.writeHeaderBuf[:])
	}

	c.writeHeader.rsv1 = false
	if flate && (opcode == opText || opcode == opBinary) {
		c.writeHeader.rsv1 = true
	}

	err = writeFrameHeader(c.writeHeader, c.bw, c.writeHeaderBuf[:])
	if err != nil {
		return 0, err