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SupportIt can be difficult to derive the correct regular expression for the problem you are trying to solve. There are many internet sites (e.g., Regular Expression Tester) and PC applications that help to construct what seems to be the right expression. However, how do you know that that expression is working properly in a production system? Sure a program can log each input string that a regex was successful for or failed on, but wouldn’t be better to see details on exactly what the regular expression was doing step by step against each input string. For this reason, we have added a regex-oriented tracing feature to P6R’s RGX™ 1.0 Regular Expression Engine.
Using the following code snippet:
p6IWRegex* pRegex = NULL;
P6UINT32 offset = 0;
P6UINT32 strLength = 0;
P6ERR err = eOk;
// * * * *
pRegex->setTrace( P6WREGEX_TRACE_BASIC );
err = pRegex->compile( P6TEXT( "[a-zA-Z09]+,?[ ]+([0-9][0-9])[ ]+([a-zA-z]+)[ ]+
([0-9][0-9][0-9][0-9])[ ]+([0-9][0-9]):([0-9][0-9]):([0-9][0-9])[ ]+([a-zA-z0-9+-]+)"),
P6MOD_NULL );
pRegex->search( P6TEXT("Wed, 02 Oct 2002 13:00:00 GMT"), P6MOD_NULL, &offset, &strLength );
pRegex->setTrace( P6WREGEX_TRACE_OFF );
we get the following trace written into a log for the successful match:
09/06/2010-15:26:05 WRegex regex: '[a-zA-Z09]+,?[ ]+([0-9][0-9])[ ]+([a-zA-z]+)[ ]+ ([0-9][0-9][0-9][0-9])[ ]+([0-9][0-9]):([0-9][0-9]):([0-9][0-9])[ ]+([a-zA-z0-9+-]+)' flavor: Perl 09/06/2010-15:26:05 WRegex function search in input string: 'Wed, 02 Oct 2002 13:00:00 GMT', using engine: Perl backtracking 09/06/2010-15:26:05 WRegex found '[a-zA-Z09]' at offset 0 09/06/2010-15:26:05 WRegex found '[a-zA-Z09]' at offset 1 09/06/2010-15:26:05 WRegex found '[a-zA-Z09]' at offset 2 09/06/2010-15:26:05 WRegex found ',' at offset 3 09/06/2010-15:26:05 WRegex found '[ ]' at offset 4 09/06/2010-15:26:05 WRegex found '[0-9]' at offset 5 09/06/2010-15:26:05 WRegex found '[0-9]' at offset 6 09/06/2010-15:26:05 WRegex found '[ ]' at offset 7 09/06/2010-15:26:05 WRegex found '[a-zA-z]' at offset 8 09/06/2010-15:26:05 WRegex found '[a-zA-z]' at offset 9 09/06/2010-15:26:05 WRegex found '[a-zA-z]' at offset 10 09/06/2010-15:26:05 WRegex found '[ ]' at offset 11 09/06/2010-15:26:05 WRegex found '[0-9]' at offset 12 09/06/2010-15:26:05 WRegex found '[0-9]' at offset 13 09/06/2010-15:26:05 WRegex found '[0-9]' at offset 14 09/06/2010-15:26:05 WRegex found '[0-9]' at offset 15 09/06/2010-15:26:05 WRegex found '[ ]' at offset 16 09/06/2010-15:26:05 WRegex found '[0-9]' at offset 17 09/06/2010-15:26:05 WRegex found '[0-9]' at offset 18 09/06/2010-15:26:05 WRegex found ':' at offset 19 09/06/2010-15:26:05 WRegex found '[0-9]' at offset 20 09/06/2010-15:26:05 WRegex found '[0-9]' at offset 21 09/06/2010-15:26:05 WRegex found ':' at offset 22 09/06/2010-15:26:05 WRegex found '[0-9]' at offset 23 09/06/2010-15:26:05 WRegex found '[0-9]' at offset 24 09/06/2010-15:26:05 WRegex found '[ ]' at offset 25 09/06/2010-15:26:05 WRegex found '[a-zA-z0-9+-]' at offset 26 09/06/2010-15:26:05 WRegex found '[a-zA-z0-9+-]' at offset 27 09/06/2010-15:26:05 WRegex found '[a-zA-z0-9+-]' at offset 28
This tracing feature can be turned on when the regular expression component is created and/or can be turned on/off by the component method p6IWRegex::setTrace(); Thus this type of tracing can be done programatically based on whatever conditions the developer or QA engineer chooses. This dynamic tracing is useful for automatic test tools to help detect a bug and provide detailed information to the developer to aid in its repair.
All P6R products are designed with the developer and QA engineer in mind. Our goal is to make development of complex software systems easier. The inclusion of a detailed, regex-oriented tracing feature in our regular expression engine helps to achieve this goal.
