RegexMatcher 1.1.0

RegexMatcher

Regex Matching Library in C#

RegexMatcher is a library that maintains an ordered list of Regex and object pairs. Populate it with a series of Regex and the objects that should be returned when a match is found while evaluating some input. All methods are thread-safe.

For examples exercising every API, refer to the test suites in src/Test.Shared.

Help or Feedback

Do you need help or have feedback? Contact me at joel at maraudersoftware.com dot com or file an issue here!

New in v1.1.0

• ValueExists compares values with Object.Equals, so equal strings and boxed value types are found
• Get returns a snapshot copy that is safe to enumerate while other threads modify the matcher
• Entries are always evaluated in the order they were added, including after removals
• Retargeted to .NET 8.0 and .NET 10.0 (plus .NET Standard 2.0/2.1 and .NET Framework 4.6.2/4.8)

Refer to CHANGELOG.md for upgrade notes.

Important Notes

Always add Regex and return object in order from most specific to least specific. Entries are evaluated in the order they were added; with the default MatchPreference of First, the first match found is used and the associated object is returned.

Regular expressions are identified by instance. Two distinct Regex instances with the same pattern are separate entries, and Exists and Remove require the same instance that was passed to Add. Adding the same instance twice throws ArgumentException.

Match and AllMatches throw ArgumentNullException for null or empty input. A RegexMatchTimeoutException from a Regex constructed with a timeout is passed through to the caller.

Simple Example

using RegexMatcher;

static void Main(string[] args)
{
    Matcher matcher = new Matcher();

    // preload a few
    matcher.Add(new Regex("^/foo/\\d+$"), "foo with id");
    matcher.Add(new Regex("^/foo/?$"), "foo with optional slash");
    matcher.Add(new Regex("^/foo$"), "foo alone");
    matcher.Add(new Regex("^/bar/(.*?)/(.*?)/?$"), "bar with two children");
    matcher.Add(new Regex("^/bar/(.*?)/?$"), "bar with one child");
    matcher.Add(new Regex("^/bar/\\d+$"), "bar with id");
    matcher.Add(new Regex("^/bar/?$"), "bar with optional slash");
    matcher.Add(new Regex("^/bar$"), "bar alone");

    if (matcher.Match("/bar/child/foo", out object val1))
    { 
        // val is "bar with two children" 
    }

    if (matcher.Match("/foo/36", out object val2))
    { 
        // val is "foo with id" 
    }

    if (matcher.Match("/unknown", out object val3)) 
    { 
        // won't get here
    }
    else
    {
        Console.WriteLine("Not found");
    }
}

Regular Expression Notes

RegexMatcher uses standard C#/.NET regular expressions. I tested primarily against simple regular expressions with values that would be encountered as raw URLs/paths and it worked well.

Some notes that I found helpful which may help you too:

• ^ is a starting anchor, useful when indicating that the pattern must be matched at the start of the input
• $ is an ending anchor, useful when indicating that the pattern must be matched at the end of the input
• (.*?) will match any input string
• \\d+ will match any number
• \\ the escape character must be used when matching certain characters as a literal
• ? marks the previous character or expression as optional

Multiple Matches

The library behavior when multiple matches are found can be configured using the Matcher.MatchPreference property.

• First (default) returns the value for the first matching regex, in insertion order
• LongestFirst returns the value for the matching regex with the longest pattern string, which usually indicates the most specific pattern
• ShortestFirst returns the value for the matching regex with the shortest pattern string

LongestFirst and ShortestFirst compare the length of the regex pattern text, not the length of the matched input. Ties go to the entry added first. AllMatches ignores MatchPreference and returns every matching value in insertion order.

Helpful links:

• https://msdn.microsoft.com/en-us/library/gg578045(v=vs.110).aspx
• https://msdn.microsoft.com/en-us/library/h5181w5w(v=vs.110).aspx

Running Tests

Tests are written once as Touchstone descriptors in src/Test.Shared and run through any of three runners:

# Console runner (exit code 0 on success, 1 on failure)
dotnet run --project src/Test.Automated -f net8.0

# Export results to JSON
dotnet run --project src/Test.Automated -f net8.0 -- --results results.json

# xUnit and NUnit runners
dotnet test src/Test.Xunit
dotnet test src/Test.Nunit

Version History

Refer to CHANGELOG.md for version history.