Simian is a software that detects duplicates in files such as C, C++, Java etc. programming languages and even plain text files.

Here is a demonstrate of c/p detection on Libre Office bug tdf#39593: copy/paste code detector/fixing.

To get a space separated list of .cxx files, run:

find <directory> -name "*.cxx" | grep -v unxlng | tr '\n' ' ' > files

All .cxx file names have been written to files.txt. The Simian call to get code pieces with at least 30 equivalent is for example:

java -jar simian-2.3.31.jar -threshold=30 -language=c++ `cat files`

Output would be:

Found 34 duplicate lines with fingerprint fda93f5a150ea8d915b59a498eac4979 in the following files:
 Between lines 639 and 726 in /.../core/vcl/source/bitmap/bitmap.cxx
 Between lines 766 and 853 in /.../core/vcl/source/bitmap/bitmap.cxx
 
Found 45 duplicate lines with fingerprint fda93f5a150ea8d915b59a498eac4979 in the following files: 
 Between lines 1468 and 1538 in /.../core/sw/qa/extras/uiwriter/uiwriter2.cxx
 Between lines 1381 and 1451 in /.../core/sw/qa/extras/uiwriter/uiwriter2.cxx

Found 59 duplicate lines with fingerprint fda93f5a150ea8d915b59a498eac4979 in the following files:
 Between lines 1748 and 1820 in /.../core/sc/qa/unit/pivottable_filters_test.cxx
 Between lines 2278 and 2350 in /.../core/sc/qa/unit/pivottable_filters_test.cxx
 
Found 75 duplicate lines with fingerprint 026938a138dede7a72201d666a827760 in the following files:
 Between lines 932 and 1049 in /.../core/sax/source/tools/converter.cxx
 Between lines 1060 and 1177 in /.../core/sax/source/tools/converter.cxx
 
...

We have selected /…/core/sax/source/tools/converter.cxx file to reduce c/p code. It’s clearly visible that only two lines are different on two functions. Between 932 - 1049 and 1060 - 1177 lines could shrink within one function.

/** convert ISO "duration" string to double; negative durations allowed */
bool Converter::convertDuration(double& rfTime,
                                std::u16string_view rString)
{
    std::u16string_view aTrimmed = trim(rString);
    const sal_Unicode* pStr = aTrimmed.data();

    // negative time duration?
    bool bIsNegativeDuration = false;
    if ( '-' == (*pStr) )
    { ... }

    /* ... */

    else{
    }
    return bSuccess;
}
/** convert ISO "duration" string to double; negative durations allowed */
bool Converter::convertDuration(double& rfTime,
                                std::string_view rString)
{
    std::string_view aTrimmed = trim(rString);
    const char* pStr = aTrimmed.data();

    // negative time duration?
    bool bIsNegativeDuration = false;
    if ( '-' == (*pStr) )
    { ... }

    /* ... */

    else{
    }
    return bSuccess;
}
convertDuration(double& rfTime, std::u16string_view rString)
convertDuration(double& rfTime, std::string_view rString)

Since two functions are include the same data type of rfTime variables, there is no need to create a template. However, data type of rString variables are different. Consequently, we have to create a template only for rString.

/** helper function of Converter::convertDuration */
template<typename V>
static bool convertDurationHelper(double& rfTime, V pStr)
{
    // negative time duration?
    bool bIsNegativeDuration = false;
    if ( '-' == (*pStr) )
    { ... }

    /* ... */
    
    else{
    }
    return bSuccess;
}

Finally, deleting duplicate code pieces will make the functions look even better and readable.

/** convert ISO "duration" string to double; negative durations allowed */
bool Converter::convertDuration(double& rfTime,
                                std::u16string_view rString)
{
    std::u16string_view aTrimmed = trim(rString);
    const sal_Unicode* pStr = aTrimmed.data();

    return convertDurationHelper(rfTime, pStr);
}
/** convert ISO "duration" string to double; negative durations allowed */
bool Converter::convertDuration(double& rfTime,
                                std::string_view rString)
{
    std::string_view aTrimmed = trim(rString);
    const char* pStr = aTrimmed.data();

    return convertDurationHelper(rfTime, pStr);
}

The patch can be seen at https://gerrit.libreoffice.org/c/core/+/111008. This was my first medium-size contribution to Libre Office.