public int match_main(String text, String pattern, int loc) {
    // Check for null inputs.
    if (text == null || pattern == null) {
      throw new IllegalArgumentException("Null inputs. (match_main)");
    }

    loc = Math.max(0, Math.min(loc, text.length()));
    if (text.equals(pattern)) {
      // Shortcut (potentially not guaranteed by the algorithm)
      return 0;
    } else if (text.length() == 0) {
      // Nothing to match.
      return -1;
    } else if (loc + pattern.length() <= text.length()
        && text.substring(loc, loc + pattern.length()).equals(pattern)) {
      // Perfect match at the perfect spot!  (Includes case of null pattern)
      return loc;
    } else {
      // Do a fuzzy compare.
      return match_bitap(text, pattern, loc);
    }
  }
Locate the best instance of 'pattern' in 'text' near 'loc'.
Returns -1 if no match found.

@param text The text to search.
@param pattern The pattern to search for.
@param loc The location to search around.
@return Best match index or -1.
src/burp/Utils/diff_match_patch.java