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Refactoring Teaser V

I have a treat for crappy code scavengers. Here is some code which has a Cyclomatic Complexity of 68 and NPath Complexity of 34,632 (this method is ONLY 189 lines long (154 NCSS)).

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/*
 * Main reading method
 */
public void read(final ByteBuffer byteBuffer) throws Exception {
    invalidateBuffer();
    // Check that the buffer is not bigger than 1 Megabyte. For security reasons
    // we will abort parsing when 1 Mega of queued chars was found.
    if (buffer.length() > maxBufferSize)
        throw new Exception("Stopped parsing never ending stanza");
    CharBuffer charBuffer = encoder.decode(byteBuffer);
    char[] buf = charBuffer.array();
    int readByte = charBuffer.remaining();
 
    // Just return if nothing was read
    if (readByte == 0)
        return;
 
    // Verify if the last received byte is an incomplete double byte character
    char lastChar = buf[readByte - 1];
    if (lastChar >= 0xfff0) {
        // Rewind the position one place so the last byte stays in the buffer
        // The missing byte should arrive in the next iteration. Once we have both
        // of bytes we will have the correct character
        byteBuffer.position(byteBuffer.position() - 1);
        // Decrease the number of bytes read by one
        readByte--;
        // Just return if nothing was read
        if (readByte == 0)
            return;
    }
 
    buffer.append(buf, 0, readByte);
    // Do nothing if the buffer only contains white spaces
    if (buffer.charAt(0) <= ' ' && buffer.charAt(buffer.length() - 1) <= ' ')
        if ("".equals(buffer.toString().trim())) {
            // Empty the buffer so there is no memory leak
            buffer.delete(0, buffer.length());
            return;
        }
    // Robot.
    char ch;
    boolean isHighSurrogate = false;
    for (int i = 0; i < readByte; i++) {
        ch = buf[i];
        if (ch < 0x20 && ch != 0x9 && ch != 0xA && ch != 0xD && ch != 0x0)
            // Unicode characters in the range 0x0000-0x001F other than 9, A, and D are not allowed in XML
            // We need to allow the NULL character, however, for Flash XMLSocket clients to work.
            throw new Exception("Disallowed character");
        if (isHighSurrogate) {
            if (Character.isLowSurrogate(ch))
                // Everything is fine. Clean up traces for surrogates
                isHighSurrogate = false;
            else
                // Trigger error. Found high surrogate not followed by low surrogate
                throw new Exception("Found high surrogate not followed by low surrogate");
        } else if (Character.isHighSurrogate(ch))
            isHighSurrogate = true;
        else if (Character.isLowSurrogate(ch))
            // Trigger error. Found low surrogate char without a preceding high surrogate
            throw new Exception("Found low surrogate char without a preceding high surrogate");
        if (status == XMLLightweightParser.TAIL) {
            // Looking for the close tag
            if (depth < 1 && ch == head.charAt(tailCount)) {
                tailCount++;
                if (tailCount == head.length()) {
                    // Close stanza found!
                    // Calculate the correct start,end position of the message into the buffer
                    int end = buffer.length() - readByte + i + 1;
                    String msg = buffer.substring(startLastMsg, end);
                    // Add message to the list
                    foundMsg(msg);
                    startLastMsg = end;
                }
            } else {
                tailCount = 0;
                status = XMLLightweightParser.INSIDE;
            }
        } else if (status == XMLLightweightParser.PRETAIL) {
            if (ch == XMLLightweightParser.CDATA_START[cdataOffset]) {
                cdataOffset++;
                if (cdataOffset == XMLLightweightParser.CDATA_START.length) {
                    status = XMLLightweightParser.INSIDE_CDATA;
                    cdataOffset = 0;
                    continue;
                }
            } else {
                cdataOffset = 0;
                status = XMLLightweightParser.INSIDE;
            }
            if (ch == '/') {
                status = XMLLightweightParser.TAIL;
                depth--;
            } else if (ch == '!')
                // This is a <! (comment) so ignore it
                status = XMLLightweightParser.INSIDE;
            else
                depth++;
        } else if (status == XMLLightweightParser.VERIFY_CLOSE_TAG) {
            if (ch == '>') {
                depth--;
                status = XMLLightweightParser.OUTSIDE;
                if (depth < 1) {
                    // Found a tag in the form <tag />
                    int end = buffer.length() - readByte + i + 1;
                    String msg = buffer.substring(startLastMsg, end);
                    // Add message to the list
                    foundMsg(msg);
                    startLastMsg = end;
                }
            } else if (ch == '<') {
                status = XMLLightweightParser.PRETAIL;
                insideChildrenTag = true;
            } else
                status = XMLLightweightParser.INSIDE;
        } else if (status == XMLLightweightParser.INSIDE_PARAM_VALUE) {
 
            if (ch == '"')
                status = XMLLightweightParser.INSIDE;
        } else if (status == XMLLightweightParser.INSIDE_CDATA) {
            if (ch == XMLLightweightParser.CDATA_END[cdataOffset]) {
                cdataOffset++;
                if (cdataOffset == XMLLightweightParser.CDATA_END.length) {
                    status = XMLLightweightParser.OUTSIDE;
                    cdataOffset = 0;
                }
            } else
                cdataOffset = 0;
        } else if (status == XMLLightweightParser.INSIDE) {
            if (ch == XMLLightweightParser.CDATA_START[cdataOffset]) {
                cdataOffset++;
                if (cdataOffset == XMLLightweightParser.CDATA_START.length) {
                    status = XMLLightweightParser.INSIDE_CDATA;
                    cdataOffset = 0;
                    continue;
                }
            } else {
                cdataOffset = 0;
                status = XMLLightweightParser.INSIDE;
            }
            if (ch == '"')
                status = XMLLightweightParser.INSIDE_PARAM_VALUE;
            else if (ch == '>') {
                status = XMLLightweightParser.OUTSIDE;
                if (insideRootTag
                        && ("stream:stream>".equals(head.toString()) || "?xml>".equals(head.toString()) || "flash:stream>".equals(head
                                .toString()))) {
                    // Found closing stream:stream
                    int end = buffer.length() - readByte + i + 1;
                    // Skip LF, CR and other "weird" characters that could appear
                    while (startLastMsg < end && '<' != buffer.charAt(startLastMsg))
                        startLastMsg++;
                    String msg = buffer.substring(startLastMsg, end);
                    foundMsg(msg);
                    startLastMsg = end;
                }
                insideRootTag = false;
            } else if (ch == '/')
                status = XMLLightweightParser.VERIFY_CLOSE_TAG;
        } else if (status == XMLLightweightParser.HEAD) {
            if (ch == ' ' || ch == '>') {
                // Append > to head to allow searching </tag>
                head.append(">");
                if (ch == '>')
                    status = XMLLightweightParser.OUTSIDE;
                else
                    status = XMLLightweightParser.INSIDE;
                insideRootTag = true;
                insideChildrenTag = false;
                continue;
            } else if (ch == '/' && head.length() > 0) {
                status = XMLLightweightParser.VERIFY_CLOSE_TAG;
                depth--;
            }
            head.append(ch);
 
        } else if (status == XMLLightweightParser.INIT) {
            if (ch == '<') {
                status = XMLLightweightParser.HEAD;
                depth = 1;
            } else
                startLastMsg++;
        } else if (status == XMLLightweightParser.OUTSIDE)
            if (ch == '<') {
                status = XMLLightweightParser.PRETAIL;
                cdataOffset = 1;
                insideChildrenTag = true;
            }
    }
    if (head.length() > 0 && ("/stream:stream>".equals(head.toString()) || "/flash:stream>".equals(head.toString())))
        // Found closing stream:stream
        foundMsg("</stream:stream>");
}

What does this code actually do?

This method is inside a LightWeightXMLParser. It reads data from a socket channel (java nio) and collects data until data is available on the channel. When a message is complete (fully formed XML), you can retrieve messages by invoking the getMsgs() method and you can invoke areThereMsgs() method to know if at least a message is presents.

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/*
 * @return an array with all messages found
 */
public String[] getMsgs() {
    String[] res = new String[msgs.size()];
    for (int i = 0; i < res.length; i++)
        res[i] = msgs.get(i);
    msgs.clear();
    invalidateBuffer();
    return res;
}

Following Tests might help you understand the code slightly better:

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    @Override
    protected void setUp() throws Exception {
        super.setUp();
        // Create parser
        parser = new LightWeightXMLParser(CHARSET);
        // Crete byte buffer and append text
        in = ByteBuffer.allocate(4096);
    }
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    @Override
    protected void tearDown() throws Exception {
        super.tearDown();
        // Release byte buffer
        in.clear();
    }
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    public void testHeader() throws Exception {
        String msg1 = "<stream:stream to=\"localhost\" xmlns=\"jabber:client\" xmlns:stream=\"http://etherx.jabber.org/streams\" version=\"1.0\">";
        in.put(msg1.getBytes());
        in.flip();
        // Fill parser with byte buffer content and parse it
        parser.read(in);
        // Make verifications
        assertTrue("Stream header is not being correctly parsed", parser.areThereMsgs());
        assertEquals("Wrong stanza was parsed", msg1, parser.getMsgs()[0]);
    }
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    public void testHeaderWithXMLVersion() throws Exception {
        String msg1 = "<?xml version=\"1.0\"?>";
        String msg2 = "<stream:stream to=\"localhost\" xmlns=\"jabber:client\" xmlns:stream=\"http://etherx.jabber.org/streams\" version=\"1.0\">";
        in.put((msg1 + msg2).getBytes());
        in.flip();
        // Fill parser with byte buffer content and parse it
        parser.read(in);
        // Make verifications
        assertTrue("Stream header is not being correctly parsed", parser.areThereMsgs());
        String[] values = parser.getMsgs();
        assertEquals("Wrong number of parsed stanzas", 2, values.length);
        assertEquals("Wrong stanza was parsed", msg1, values[0]);
        assertEquals("Wrong stanza was parsed", msg2, values[1]);
    }
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    public void testStanzas() throws Exception {
        String msg1 = "<stream:stream to=\"localhost\" xmlns=\"jabber:client\" xmlns:stream=\"http://etherx.jabber.org/streams\" version=\"1.0\">";
        String msg2 = "<starttls xmlns=\"urn:ietf:params:xml:ns:xmpp-tls\"/>";
        String msg3 = "<stream:stream to=\"localhost\" xmlns=\"jabber:client\" xmlns:stream=\"http://etherx.jabber.org/streams\" version=\"1.0\">";
        String msg4 = "<iq id=\"428qP-0\" to=\"localhost\" type=\"get\"><query xmlns=\"jabber:iq:register\"></query></iq>";
        String msg5 = "<stream:stream to=\"localhost\" xmlns=\"jabber:client\" xmlns:stream=\"http://etherx.jabber.org/streams\" version=\"1.0\">";
        String msg6 = "<presence id=\"428qP-5\"></presence>";
        in.put(msg1.getBytes());
        in.put(msg2.getBytes());
        in.put(msg3.getBytes());
        in.put(msg4.getBytes());
        in.put(msg5.getBytes());
        in.put(msg6.getBytes());
        in.flip();
        // Fill parser with byte buffer content and parse it
        parser.read(in);
        // Make verifications
        assertTrue("Stream header is not being correctly parsed", parser.areThereMsgs());
        String[] values = parser.getMsgs();
        assertEquals("Wrong number of parsed stanzas", 6, values.length);
        assertEquals("Wrong stanza was parsed", msg1, values[0]);
        assertEquals("Wrong stanza was parsed", msg2, values[1]);
        assertEquals("Wrong stanza was parsed", msg3, values[2]);
        assertEquals("Wrong stanza was parsed", msg4, values[3]);
        assertEquals("Wrong stanza was parsed", msg5, values[4]);
        assertEquals("Wrong stanza was parsed", msg6, values[5]);
    }
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    public void testCompleteStanzas() throws Exception {
        String msg1 = "<stream:stream to=\"localhost\" xmlns=\"jabber:client\" xmlns:stream=\"http://etherx.jabber.org/streams\" version=\"1.0\">";
        String msg2 = "<starttls xmlns=\"urn:ietf:params:xml:ns:xmpp-tls\"/>";
        String msg3 = "<stream:stream to=\"localhost\" xmlns=\"jabber:client\" xmlns:stream=\"http://etherx.jabber.org/streams\" version=\"1.0\">";
        String msg4 = "<iq id=\"428qP-0\" to=\"localhost\" type=\"get\"><query xmlns=\"jabber:iq:register\"></query></iq>";
        String msg5 = "<stream:stream to=\"localhost\" xmlns=\"jabber:client\" xmlns:stream=\"http://etherx.jabber.org/streams\" version=\"1.0\">";
        String msg6 = "<presence id=\"428qP-5\"></presence>";
        String msg7 = "</stream:stream>";
        in.put(msg1.getBytes());
        in.put(msg2.getBytes());
        in.put(msg3.getBytes());
        in.put(msg4.getBytes());
        in.put(msg5.getBytes());
        in.put(msg6.getBytes());
        in.put(msg7.getBytes());
        in.flip();
        // Fill parser with byte buffer content and parse it
        parser.read(in);
        // Make verifications
        assertTrue("Stream header is not being correctly parsed", parser.areThereMsgs());
        String[] values = parser.getMsgs();
        assertEquals("Wrong number of parsed stanzas", 7, values.length);
        assertEquals("Wrong stanza was parsed", msg1, values[0]);
        assertEquals("Wrong stanza was parsed", msg2, values[1]);
        assertEquals("Wrong stanza was parsed", msg3, values[2]);
        assertEquals("Wrong stanza was parsed", msg4, values[3]);
        assertEquals("Wrong stanza was parsed", msg5, values[4]);
        assertEquals("Wrong stanza was parsed", msg6, values[5]);
        assertEquals("Wrong stanza was parsed", msg7, values[6]);
    }
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    public void testIQ() throws Exception {
        String iq = "<iq type=\"set\" to=\"lachesis\" from=\"0sups/Connection Worker - 1\" id=\"360-22348\"><session xmlns=\"http://jabber.org/protocol/connectionmanager\" id=\"0sups87b1694\"><close/></session></iq>";
        in.put(iq.getBytes());
        in.flip();
        // Fill parser with byte buffer content and parse it
        parser.read(in);
        // Make verifications
        assertTrue("Stream header is not being correctly parsed", parser.areThereMsgs());
        String parsedIQ = parser.getMsgs()[0];
        assertEquals("Wrong stanza was parsed", iq, parsedIQ);
    }
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    public void testNestedElements() throws Exception {
        String msg1 = "<message><message xmlns=\"e\">1</message></message>";
        in.put(msg1.getBytes());
        in.flip();
        // Fill parser with byte buffer content and parse it
        parser.read(in);
        // Make verifications
        assertTrue("Stream header is not being correctly parsed", parser.areThereMsgs());
        String[] values = parser.getMsgs();
        assertEquals("Wrong number of parsed stanzas", 1, values.length);
        assertEquals("Wrong stanza was parsed", msg1, values[0]);
    }
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    public void testIncompleteStanza() throws Exception {
        String msg1 = "<message><something xmlns=\"http://idetalk.com/namespace\">12";
        in.put(msg1.getBytes());
        in.flip();
        // Fill parser with byte buffer content and parse it
        parser.read(in);
        // Make verifications
        assertFalse("Found messages in incomplete stanza", parser.areThereMsgs());
    }
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    public void testStanzaWithSpecialChars() throws Exception {
        String msg1 = "<message><something xmlns=\"http://idetalk.com/namespace\">12/</something></message>";
        String msg2 = "<message><something xmlns=\"http://idetalk.com/namespace\">12///</something></message>";
        String msg3 = "<message><something xmlns=\"http://idetalk.com/namespace\">12/\\/</something></message>";
        String msg4 = "<message><something xmlns=\"http://idetalk.com/namespace\">http://idetalk.com/namespace/</something></message>";
        in.put(msg1.getBytes());
        in.put(msg2.getBytes());
        in.put(msg3.getBytes());
        in.put(msg4.getBytes());
        in.flip();
        // Fill parser with byte buffer content and parse it
        parser.read(in);
        // Make verifications
        assertTrue("No messages were found in stanza", parser.areThereMsgs());
        String[] values = parser.getMsgs();
        assertEquals("Wrong number of parsed stanzas", 4, values.length);
        assertEquals("Wrong stanza was parsed", msg1, values[0]);
        assertEquals("Wrong stanza was parsed", msg2, values[1]);
        assertEquals("Wrong stanza was parsed", msg3, values[2]);
        assertEquals("Wrong stanza was parsed", msg4, values[3]);
    }
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    public void testCompletedStanza() throws Exception {
        String msg1 = "<message><something xmlns=\"http://idetalk.com/namespace\">12";
        in.put(msg1.getBytes());
        in.flip();
        // Fill parser with byte buffer content and parse it
        parser.read(in);
        // Make verifications
        assertFalse("Found messages in incomplete stanza", parser.areThereMsgs());
 
        String msg2 = "</something></message>";
        ByteBuffer in2 = ByteBuffer.allocate(4096);
        in2.put(msg2.getBytes());
        in2.flip();
        // Fill parser with byte buffer content and parse it
        parser.read(in2);
        in2.clear();
        assertTrue("Stream header is not being correctly parsed", parser.areThereMsgs());
        String[] values = parser.getMsgs();
        assertEquals("Wrong number of parsed stanzas", 1, values.length);
        assertEquals("Wrong stanza was parsed", msg1 + msg2, values[0]);
    }
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    public void testStanzaWithComments() throws Exception {
        String msg1 = "<iq from=\"lg@jabber.org/spark\"><query xmlns=\"jabber:iq:privacy\"><!-- silly comment --></query></iq>";
        in.put(msg1.getBytes());
        in.flip();
        // Fill parser with byte buffer content and parse it
        parser.read(in);
        // Make verifications
        assertTrue("No messages were found in stanza", parser.areThereMsgs());
        String[] values = parser.getMsgs();
        assertEquals("Wrong number of parsed stanzas", 1, values.length);
        assertEquals("Wrong stanza was parsed", msg1, values[0]);
    }
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    public void testWeirdoContent() throws Exception {
        final String[] testStanzas = { "<?xml version=\"1.0\"?>",
                "<stream:stream xmlns:stream=\"http://etherx.jabber.org/streams\" xmlns=\"jabber:client\" to=\"localhost\" >",
                "<emppartag test=\"1\"/>", "<cdatatest><![CDATA[just<ignore everything& >>here<<<<< /> />]]&gt;]]></cdatatest>",
                "<esctest param=\"1\"> this \" is / a test /> test /> </esctest>",
                "<comtest>this <!-- comment --> is a comment</comtest>", "<emptag/>",
                "<iq type=\"get\" id=\"aab1a\" ><query xmlns=\"jabber:iq:roster\"/> <tag> text </tag></iq>",
                "<iq type=\"get\" id=\"aab1a\" ><query xmlns=\"jabber:iq:roster\"/> </iq>",
                "<message><body xmlns=\"http://idetalk.com/namespace\">12\"</body></message>",
                "<message to=\"lg@jabber.org\" id=\"XRk8p-X\"><body> /> /> </body></message>", };
        String testMsg = "";
        for (String s : testStanzas)
            testMsg += s;
        ByteBuffer mybuffer = ByteBuffer.wrap(testMsg.getBytes());
        parser.read(mybuffer);
 
        String[] msgs = parser.getMsgs();
        for (int i = 0; i < testStanzas.length; i++) {
            assertTrue(i < msgs.length);
            assertEquals(testStanzas[i], msgs[i]);
        }
    }
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    public void testRead() {
        try {
            LightWeightXMLParser parser = new LightWeightXMLParser("UTF-8");
            String xml1 = "<ab>\u1000</a";
            String xml2 = "b>";
            ByteBuffer buffer1 = ByteBuffer.wrap(xml1.getBytes("UTF-8"));
            ByteBuffer buffer2 = ByteBuffer.wrap(xml2.getBytes("UTF-8"));
 
            parser.read(buffer1);
            parser.read(buffer2);
 
            if (!parser.areThereMsgs())
                Assert.fail("No messages found");
 
            String msgs[] = parser.getMsgs();
            if (msgs.length > 1)
                Assert.fail("More than one message found");
            else
                Assert.assertEquals(xml1 + xml2, msgs[0]);
        } catch (Exception e) {
            Assert.fail(e.getMessage());
        }
    }

Feel free to download the full project source code.


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