QregExp for IPv4 address (xxx.xxx.xxx.xxx)

[MarkoSan]

In my Application, I have log window (subclassed QPlainTextEdit with syntax highlighting, based on Sytnax Highlighter Example. I've implemented three types of log info entry:

• [INFO] - Info type log entry begins with QString containing "[INFO]"

• [WARNING] - Info type log entry begins with QString containing "[WARNING]"

• [ERROR] - Info type log entry begins with QString containing "[ERROR]"

Based on log info type, the color of entry is applied - blue (INFO), yellow (WARNING) and red (ERROR). This all works perfectly. Now, the log entry contents continues with time stamp, as you can see from following class static method:

const QString UeLogWindow::ueCreateLogEntry(const quint8& logEntryType,
                                            const QString& logText)
{
    // TODO improve logEntryType - work with enum
    // TODO remove appended ip address
    QString result=QString();
    QString timeStamp=QDateTime::currentDateTime().toString("dd.MM.yyyy hh:mm:ss:zzz");

    switch(logEntryType)
    {
        case 0:
        {
            result=tr("[INFO]");

            break;
        }   // case

        case 1:
        {
            result=tr("[WARNING]");

            break;
        }   // case

        case 2:
        {
            result=tr("[ERROR]");

            break;
        }   // case

        default:
        {
            break;
        }   // default
    }   // switch

    result.append(" ")
          .append(timeStamp)
          .append(" ")
          .append(logText)
          .append(" ")
          .append("192.168.100.1"); // only for test purposes to see if  highlighting is working

    return result;
}   // ueCreateLogEntry

Now, here are my sytnax highlighting rules:

UeLogWindowTextHighlighter::UeLogWindowTextHighlighter(QTextDocument* const parent)
    : QSyntaxHighlighter (parent)
{
    UeHighlightRule ruleInfo;
    UeHighlightRule ruleWarning;
    UeHighlightRule ruleError;
    UeHighlightRule ruleIPv4Address;

    QTextCharFormat ruleInfoFormat;
    QTextCharFormat ruleWarningFormat;
    QTextCharFormat ruleErrorFormat;
    QTextCharFormat ruleIPv4AddressFormat;

    ruleInfoFormat.setForeground(Qt::darkBlue);
    ruleInfoFormat.setFontWeight(QFont::ExtraLight);
    ruleInfo.pattern=QRegExp("^\\[INFO\\].*");
    ruleInfo.format=ruleInfoFormat;

    ruleWarningFormat.setForeground(Qt::darkYellow);
    ruleWarningFormat.setFontWeight(QFont::Normal);
    ruleWarning.pattern=QRegExp("^\\[WARNING\\].*");
    ruleWarning.format=ruleWarningFormat;

    ruleErrorFormat.setForeground(Qt::darkRed);
    ruleErrorFormat.setFontWeight(QFont::ExtraBold);
    ruleError.pattern=QRegExp("^\\[ERROR\\].*");
    ruleError.format=ruleErrorFormat;

    ruleIPv4AddressFormat.setFontWeight(QFont::ExtraBold);
    ruleIPv4Address.pattern=QRegExp("(\\d{1,3}.\\d{1,3}.\\d{1,3}.\\d{1,3})");
    ruleIPv4Address.format=ruleIPv4AddressFormat;

    m_ueHighlightRules.append(ruleInfo);
    m_ueHighlightRules.append(ruleWarning);
    m_ueHighlightRules.append(ruleError);
    m_ueHighlightRules.append(ruleIPv4Address);
}   // constructor

Now, ruleIPv4Address also affects my timestamp beside ip address itself in log entry:

How do I change regular expression to avoid affecting my timestamp?

[micland]

I think you have to escape the point character because it's treated as "any character" in a reg exp. (prefix it with an escaped backslash: QRegExp("(\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}\\.\\d{1,3})");)

[VRonin]

. should be escaped
"(\\d{1,3}.\\d{1,3}.\\d{1,3}.\\d{1,3})" should become "(\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}\\.\\d{1,3})"

On a separate note, if you are using Qt5, you should use QregularExpression instead of QRegExp

Edit:
@micland was faster on the draw

Edit2:
I think your internationalisation will break the syntax highlight (e.g. if WARNING becomes ATTENTION in French the regular expression will not match anymore)

Edit3:
Your regexp will match invalid IP addresses (500.1.1.0 should not match) see here: https://www.safaribooksonline.com/library/view/regular-expressions-cookbook/9780596802837/ch07s16.html for the correct pattern

[MarkoSan]

@VRonin said:

. should be escaped
"(\\d{1,3}.\\d{1,3}.\\d{1,3}.\\d{1,3})" should become "(\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}\\.\\d{1,3})"

On a separate note, if you are using Qt5, you should use QregularExpression instead of QRegExp

Edit:
@micland was faster on the draw

Edit2:
I think your internationalisation will break the syntax highlight (e.g. if WARNING becomes ATTENTION in French the regular expression will not match anymore)

Edit3:
Your regexp will match invalid IP addresses (500.1.1.0 should not match) see here: https://www.safaribooksonline.com/library/view/regular-expressions-cookbook/9780596802837/ch07s16.html for the correct pattern

You have strong good point by commenting break of syntax highlight because of internationalisation, are there any solutions for current code?

[VRonin]

@MarkoSan said:

are there any solutions for current code?

either you enclose the RegExp pattern in tr() and trust the translator to do the right thing or you declare

private:
const QString logTags[3];

then in the constructor add the initialisation

UeLogWindow::UeLogWindow(QWidget parent)
:  \\ ... other inits
, logTags{tr("[INFO]"),tr("[WARNING]"),tr("[ERROR]")}

(if you don't have access to C++11 functionality you should not declare const and initialise the members with the usual [] operator)

this also simplifies a lot the switch(logEntryType) part

to use them in the regular expression you then just have to call QRegularExpression::escape(). for example, ruleError.pattern=QRegExp("^\\[ERROR\\].*"); would become

ruleError.pattern=QRegExp("^"+QRegExp::escape(logEntryType[2])+".*");

Again, here I used QRegExp but you should REALLY use QRegularExpression especially if you expect a big number of matches