boyermoore

The Boyer-Moore string matching algorithm.

Ported to ruby from wikipedia's c code, but geared towards a token search rather than merely characters.

Usage:

BoyerMoore.search(haystack, needle)   # returns index of needle or nil

Examples:

Basic search in string:

BoyerMoore.search("ANPANMAN", "ANP")   # => 0
BoyerMoore.search("ANPANMAN", "ANPXX") # => nil 
BoyerMoore.search("foobar", "bar")     # => 3

You can also search an array of tokens:

BoyerMoore.search(["<b>", "hi", "</b>"], ["hi"])         # => 1 
BoyerMoore.search(["bam", "foo", "bar"], ["foo", "bar"]) # => 1 
BoyerMoore.search(["bam", "bar", "baz"], ["foo"])        # => nil 

A token can be a regular expression:

BoyerMoore.search(["Sing", "99", "Luftballon"], [/\d+/]) == 1
BoyerMoore.search(["Nate Murray", "5 Pine Street", "Los Angeles", "CA", "90210"], [/^\w{2}$/, /^\d{5}$/]) == 3 

Notes

The regular-expression token matching is a bit of a hack and will be fairly slow because every hash miss is compared against every regular expression key. You probably shouldn't use the regular expression token search for anything more than a toy.

Credits

• Written by Nate Murray http://www.xcombinator.com
• But based almost entirely on wikipedia's c code
• Originally I was using Arne's code here but eventually I decided to scrap it and use the wikipedia code directly.