multiregexp

multiregexp is a more efficient way to match several regular expressions.

It offers a more performant alternative to the anti-pattern of looping on patterns. (This anti-pattern often happens when routing urls, building reports out of logs, searching for terms in a text, etc.)

    for (final Pattern pattern: patterns) {
        final Matcher matcher = pattern.matcher(txt);
        // ...
    }

When using multiregexp, your regular expressions are compiled in once single (possible big) deterministic automaton.

This library relies on dk.brics.automaton for all the heavy lifting.

More explanation is available in this blog post.

Disclaimer

At the moment, MultiRegexp relies on dk.brics.automaton to compile the individual regular expressions.

It therefore presents the same limitations as this library :

• Only a subset of the java regular expression language is handled.
• Some character are required to be escaped, even though it is not an issue for Java's pattern.
• The library does not handle groups.

This may change in the future.

Benchmark

Following the benchmark described in http://lh3lh3.users.sourceforge.net/reb.shtml, we searched for URIs, email and dates using the following patterns.

Groups have been exchanged for anonymous groups to make sure Java was not penalized. The pattern chosen here are not especially pathological.

URI (protocol://server/path): [a-zA-Z][a-zA-Z0-9]*://[^ /]+(?:/[^ ]*)?
Email (name@server): [^ \@]+\@[^ \@]+
Date (month/day/year): [0-9][0-9]?/[0-9][0-9]?/[0-9][0-9](?:[0-9][0-9])?

We measured the time to search for these 3 regular expression in a 40MB file :

Java's Pattern
build time (ms): 2ms
match time (ms): 2.5s

dku.brics.automaton
build time (ms): 35ms
match time (ms): 1s

multipattern
build time (ms): 60ms
match time (ms): 105ms

Using it in your maven project

Add the following lines in the dependencies section of your pom.xml file.

    <dependency>
        <groupId>com.fulmicoton</groupId>
        <artifactId>multiregexp</artifactId>
        <version>0.3</version>
    </dependency>

Matching

	import com.fulmicoton.multiregexp.MultiPatternMatcher;
	import com.fulmicoton.multiregexp.MultiPattern;


	// This is an equivalent to Pattern.compile(...)
	// You need to cache this object if you want to 
	// search on more than one string.
    MultiPatternMatcher matcher = MultiPattern.of(
            "ab+",     // 0
            "abc+",    // 1
            "ab?c",    // 2
            "v",       // 3
            "v.*",     // 4
            "(def)+"   // 5
    ).matcher();
    int[] matching = multiPattern.match("abc"); // return {1, 2}

Searching

	import com.fulmicoton.multiregexp.MultiPatternSearcher;
	import com.fulmicoton.multiregexp.MultiPattern;

	// The searcher will 
    MultiPatternSearcher matcher = MultiPattern.of(
            "ab+",     // 0
            "abc+",    // 1
            "ab?c",    // 2
            "v",       // 3
            "v.*",     // 4
            "(def)+"   // 5
    ).searcher();
    MultiPatternSearcher.Cursor cursor = multiPatternSearcher.search("ab abc vvv");
    while (cursor.next()) {
    	int[] pattern cursor.matches();   // array with the pattern id which match ends at this position
        int start = cursor.start();
        int end = cursor.end();
    }