decode() — netty Function Reference

Source Code

codec-http/src/main/java/io/netty/handler/codec/http/websocketx/WebSocket08FrameDecoder.java lines 160–390

    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
        // Discard all data received if closing handshake was received before.
        if (receivedClosingHandshake) {
            in.skipBytes(actualReadableBytes());
            return;
        }

        switch (state) {
        case READING_FIRST:
            if (!in.isReadable()) {
                return;
            }

            framePayloadLength = 0;

            // FIN, RSV, OPCODE
            byte b = in.readByte();
            frameFinalFlag = (b & 0x80) != 0;
            frameRsv = (b & 0x70) >> 4;
            frameOpcode = b & 0x0F;

            if (logger.isTraceEnabled()) {
                logger.trace("Decoding WebSocket Frame opCode={}", frameOpcode);
            }

            state = State.READING_SECOND;
        case READING_SECOND:
            if (!in.isReadable()) {
                return;
            }
            // MASK, PAYLOAD LEN 1
            b = in.readByte();
            frameMasked = (b & 0x80) != 0;
            framePayloadLen1 = b & 0x7F;

            if (frameRsv != 0 && !config.allowExtensions()) {
                protocolViolation(ctx, in, "RSV != 0 and no extension negotiated, RSV:" + frameRsv);
                return;
            }

            if (!config.allowMaskMismatch() && config.expectMaskedFrames() != frameMasked) {
                protocolViolation(ctx, in, "received a frame that is not masked as expected");
                return;
            }

            if (frameOpcode > 7) { // control frame (have MSB in opcode set)

                // control frames MUST NOT be fragmented
                if (!frameFinalFlag) {
                    protocolViolation(ctx, in, "fragmented control frame");
                    return;
                }

                // control frames MUST have payload 125 octets or less
                if (framePayloadLen1 > 125) {
                    protocolViolation(ctx, in, "control frame with payload length > 125 octets");
                    return;
                }

                // check for reserved control frame opcodes
                if (!(frameOpcode == OPCODE_CLOSE || frameOpcode == OPCODE_PING
                      || frameOpcode == OPCODE_PONG)) {
                    protocolViolation(ctx, in, "control frame using reserved opcode " + frameOpcode);
                    return;
                }

                // close frame : if there is a body, the first two bytes of the
                // body MUST be a 2-byte unsigned integer (in network byte
                // order) representing a getStatus code
                if (frameOpcode == 8 && framePayloadLen1 == 1) {
                    protocolViolation(ctx, in, "received close control frame with payload len 1");
                    return;
                }
            } else { // data frame
                // check for reserved data frame opcodes
                if (!(frameOpcode == OPCODE_CONT || frameOpcode == OPCODE_TEXT
                      || frameOpcode == OPCODE_BINARY)) {
                    protocolViolation(ctx, in, "data frame using reserved opcode " + frameOpcode);
                    return;
                }