XmlFrameDecoder Class — netty Architecture

Source Code

codec-xml/src/main/java/io/netty/handler/codec/xml/XmlFrameDecoder.java lines 78–245

public class XmlFrameDecoder extends ByteToMessageDecoder {

    private final int maxFrameLength;

    public XmlFrameDecoder(int maxFrameLength) {
        this.maxFrameLength = checkPositive(maxFrameLength, "maxFrameLength");
    }

    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
        boolean openingBracketFound = false;
        boolean atLeastOneXmlElementFound = false;
        boolean inCDATASection = false;
        long openBracketsCount = 0;
        int length = 0;
        int leadingWhiteSpaceCount = 0;
        final int bufferLength = in.writerIndex();

        if (bufferLength > maxFrameLength) {
            // bufferLength exceeded maxFrameLength; dropping frame
            in.skipBytes(in.readableBytes());
            fail(bufferLength);
            return;
        }

        for (int i = in.readerIndex(); i < bufferLength; i++) {
            final byte readByte = in.getByte(i);
            if (!openingBracketFound && Character.isWhitespace(readByte)) {
                // xml has not started and whitespace char found
                leadingWhiteSpaceCount++;
            } else if (!openingBracketFound && readByte != '<') {
                // garbage found before xml start
                fail(ctx);
                in.skipBytes(in.readableBytes());
                return;
            } else if (!inCDATASection && readByte == '<') {
                openingBracketFound = true;

                if (i < bufferLength - 1) {
                    final byte peekAheadByte = in.getByte(i + 1);
                    if (peekAheadByte == '/') {
                        // found </, we must check if it is enclosed
                        int peekFurtherAheadIndex = i + 2;
                        while (peekFurtherAheadIndex <= bufferLength - 1) {
                            //if we have </ and enclosing > we can decrement openBracketsCount
                            if (in.getByte(peekFurtherAheadIndex) == '>') {
                                openBracketsCount--;
                                break;
                            }
                            peekFurtherAheadIndex++;
                        }
                    } else if (isValidStartCharForXmlElement(peekAheadByte)) {
                        atLeastOneXmlElementFound = true;
                        // char after < is a valid xml element start char,
                        // incrementing openBracketsCount
                        openBracketsCount++;
                    } else if (peekAheadByte == '!') {
                        if (isCommentBlockStart(in, i)) {
                            // <!-- comment --> start found
                            openBracketsCount++;
                        } else if (isCDATABlockStart(in, i)) {
                            // <![CDATA[ start found
                            openBracketsCount++;
                            inCDATASection = true;
                        }
                    } else if (peekAheadByte == '?') {
                        // <?xml ?> start found
                        openBracketsCount++;
                    }
                }
            } else if (!inCDATASection && readByte == '/') {
                if (i < bufferLength - 1 && in.getByte(i + 1) == '>') {
                    // found />, decrementing openBracketsCount
                    openBracketsCount--;
                }
            } else if (readByte == '>') {
                length = i + 1;

                if (i - 1 > -1) {
                    final byte peekBehindByte = in.getByte(i - 1);