user/src/com/google/gwt/regexp/shared/RegExp.java - gwt - Git at Google

 /*
  * Copyright 2010 Google Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License"); you may not
  * use this file except in compliance with the License. You may obtain a copy of
  * the License at
  *
  * http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
  * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
  * License for the specific language governing permissions and limitations under
  * the License.
  */
 package com.google.gwt.regexp.shared;

 import java.util.ArrayList;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;

 /**
  * A class for regular expressions with features like Javascript's RegExp, plus
  * Javascript String's replace and split methods (which can take a RegExp
  * parameter). The pure Java implementation (for server-side use) uses Java's
  * Pattern class, unavailable under GWT. The super-sourced GWT implementation
  * simply calls on to the native Javascript classes.
  * <p>
  * There are a few small incompatibilities between the two implementations.
  * Java-specific constructs in the regular expression syntax (e.g. [a-z&&[^bc]],
  * (?<=foo), \A, \Q) work only in the pure Java implementation, not the GWT
  * implementation, and are not rejected by either. Also, the Javascript-specific
  * constructs $` and $' in the replacement expression work only in the GWT
  * implementation, not the pure Java implementation, which rejects them.
  */
 public class RegExp {

   // In JS syntax, a \ in the replacement string has no special meaning.
   // In Java syntax, a \ in the replacement string escapes the next character,
   // so we have to translate \ to \\ before passing it to Java.
   private static final Pattern REPLACEMENT_BACKSLASH = Pattern.compile("\\\\");
   // To get \\, we have to say \\\\\\\\:
   // \\\\\\\\ --> Java string unescape --> \\\\
   // \\\\ ---> Pattern replacement unescape in replacement preprocessing --> \\
   private static final String REPLACEMENT_BACKSLASH_FOR_JAVA = "\\\\\\\\";

   // In JS syntax, a $& in the replacement string stands for the whole match.
   // In Java syntax, the equivalent is $0, so we have to translate $& to
   // $0 before passing it to Java. However, we have to watch out for $$&, which
   // is actually a Javascript $$ (see below) followed by a & with no special
   // meaning, and must not get translated.
   private static final Pattern REPLACEMENT_DOLLAR_AMPERSAND =
       Pattern.compile("((?:^|\\G|[^$])(?:\\$\\$)*)\\$&");
   private static final String REPLACEMENT_DOLLAR_AMPERSAND_FOR_JAVA = "$1\\$0";

   // In JS syntax, a $` and $' in the replacement string stand for everything
   // before the match and everything after the match.
   // In Java syntax, there is no equivalent, so we detect and reject $` and $'.
   // However, we have to watch out for $$` and $$', which are actually a JS $$
   // (see below) followed by a ` or ' with no special meaning, and must not be
   // rejected.
   private static final Pattern REPLACEMENT_DOLLAR_APOSTROPHE =
       Pattern.compile("(?:^|[^$])(?:\\$\\$)*\\$[`']");

   // In JS syntax, a $$ in the replacement string stands for a (single) dollar
   // sign, $.
   // In Java syntax, the equivalent is \$, so we have to translate $$ to \$
   // before passing it to Java.
   private static final Pattern REPLACEMENT_DOLLAR_DOLLAR =
       Pattern.compile("\\$\\$");
   // To get \$, we have to say \\\\\\$:
   // \\\\\\$ --> Java string unescape --> \\\$
   // \\\$ ---> Pattern replacement unescape in replacement preprocessing --> \$
   private static final String REPLACEMENT_DOLLAR_DOLLAR_FOR_JAVA = "\\\\\\$";

   /**
    * Creates a regular expression object from a pattern with no flags.
    *
    * @param pattern the Javascript regular expression pattern to compile
    * @return a new regular expression
    * @throws RuntimeException if the pattern is invalid
    */
   public static RegExp compile(String pattern) {
     return compile(pattern, "");
   }

   /**
    * Creates a regular expression object from a pattern using the given flags.
    *
    * @param pattern the Javascript regular expression pattern to compile
    * @param flags the flags string, containing at most one occurrence of {@code
    *        'g'} ({@link #getGlobal()}), {@code 'i'} ({@link #getIgnoreCase()}),
    *        or {@code 'm'} ({@link #getMultiline()}).
    * @return a new regular expression
    * @throws RuntimeException if the pattern or the flags are invalid
    */
   public static RegExp compile(String pattern, String flags) {
     // Parse flags
     boolean globalFlag = false;
     int javaPatternFlags = Pattern.UNIX_LINES;
     for (char flag : parseFlags(flags)) {
       switch (flag) {
         case 'g':
           globalFlag = true;
           break;

         case 'i':
           javaPatternFlags |= Pattern.CASE_INSENSITIVE | Pattern.UNICODE_CASE;
           break;

         case 'm':
           javaPatternFlags |= Pattern.MULTILINE;
           break;

         default:
           throw new IllegalArgumentException("Unknown regexp flag: '" + flag
               + "'");
       }
     }

     Pattern javaPattern = Pattern.compile(pattern, javaPatternFlags);

     return new RegExp(pattern, javaPattern, globalFlag);
   }

   /**
    * Parses a flags string as a set of characters. Does not reject unknown
    * flags.
    *
    * @param flags the flag string to parse
    * @return a set of flags
    * @throws IllegalArgumentException if a flag is duplicated
    */
   private static Set<Character> parseFlags(String flags) {
     Set<Character> flagsSet = new HashSet<Character>(flags.length());
     for (int flagIndex = 0; flagIndex < flags.length(); flagIndex++) {
       char flag = flags.charAt(flagIndex);
       if (!flagsSet.add(flag)) {
         throw new IllegalArgumentException("Flag cannot be specified twice: '"
             + flag + "'");
       }
     }
     return flagsSet;
   }

   private final boolean globalFlag;

   private int lastIndex;

   private final Pattern pattern;

   private final String source;

   private RegExp(String source, Pattern pattern, boolean globalFlag) {
     this.source = source;
     this.pattern = pattern;
     this.globalFlag = globalFlag;
     lastIndex = 0;
   }

   /**
    * Applies the regular expression to the given string. This call affects the
    * value returned by {@link #getLastIndex()} if the global flag is set.
    *
    * @param input the string to apply the regular expression to
    * @return a match result if the string matches, else {@code null}
    */
   public MatchResult exec(String input) {
     // Start the search at lastIndex if the global flag is true.
     int searchStartIndex = (globalFlag) ? lastIndex : 0;

     Matcher matcher;
     if (input == null || searchStartIndex < 0
         || searchStartIndex > input.length()) {
       // Avoid exceptions: Javascript is more tolerant than Java
       matcher = null;
     } else {
       matcher = pattern.matcher(input);
       if (!matcher.find(searchStartIndex)) {
         matcher = null;
       }
     }

     if (matcher != null) {
       // Match: create a result

       // Retrieve the matched groups.
       int groupCount = matcher.groupCount();
       List<String> groups = new ArrayList<String>(1 + groupCount);
       for (int group = 0; group <= groupCount; group++) {
         groups.add(matcher.group(group));
       }

       if (globalFlag) {
         lastIndex = matcher.end();
       }

       return new MatchResult(matcher.start(), input, groups);
     } else {
       // No match
       if (globalFlag) {
         lastIndex = 0;
       }
       return null;
     }
   }

   /**
    * Returns whether the regular expression captures all occurrences of the
    * pattern.
    */
   public boolean getGlobal() {
     return globalFlag;
   }

   /**
    * Returns whether the regular expression ignores case.
    */
   public boolean getIgnoreCase() {
     return (pattern.flags() & Pattern.CASE_INSENSITIVE) != 0;
   }

   /**
    * Returns the zero-based position at which to start the next match. The
    * return value is not defined if the global flag is not set. After a call
    * to {@link #exec(String)} or {@link #test(String)}, this method returns
    * the next position following the most recent match.
    *
    * @see #getGlobal()
    */
   public int getLastIndex() {
     return lastIndex;
   }

   /**
    * Returns whether '$' and '^' match line returns ('\n' and '\r') in addition
    * to the beginning or end of the string.
    */
   public boolean getMultiline() {
     return (pattern.flags() & Pattern.MULTILINE) != 0;
   }

   /**
    * Returns the pattern string of the regular expression.
    */
   public String getSource() {
     return source;
   }

   /**
    * Returns the input string with the part(s) matching the regular expression
    * replaced with the replacement string. If the global flag is set, replaces
    * all matches of the regular expression. Otherwise, replaces the first match
    * of the regular expression. As per Javascript semantics, backslashes in the
    * replacement string get no special treatment, but the replacement string can
    * use the following special patterns:
    * <ul>
    * <li>$1, $2, ... $99 - inserts the n'th group matched by the regular
    * expression.
    * <li>$&amp; - inserts the entire string matched by the regular expression.
    * <li>$$ - inserts a $.
    * </ul>
    * Note: $` and $' are *not* supported in the pure Java implementation, and
    * throw an exception.
    *
    * @param input the string in which the regular expression is to be searched.
    * @param replacement the replacement string.
    * @return the input string with the regular expression replaced by the
    *         replacement string.
    * @throws RuntimeException if {@code replacement} is invalid
    */
   public String replace(String input, String replacement) {
     // Replace \ in the replacement with \\ to escape it for Java replace.
     replacement = REPLACEMENT_BACKSLASH.matcher(replacement).replaceAll(
         REPLACEMENT_BACKSLASH_FOR_JAVA);

     // Replace the Javascript-ese $& in the replacement with Java-ese $0, but
     // watch out for $$&, which should stay $$&, to be changed to \$& below.
     replacement = REPLACEMENT_DOLLAR_AMPERSAND.matcher(replacement).replaceAll(
         REPLACEMENT_DOLLAR_AMPERSAND_FOR_JAVA);

     // Test for Javascript-ese $` and $', which we do not support in the pure
     // Java version.
     if (REPLACEMENT_DOLLAR_APOSTROPHE.matcher(replacement).find()) {
       throw new UnsupportedOperationException(
           "$` and $' replacements are not supported");
     }

     // Replace the Javascript-ese $$ in the replacement with Java-ese \$.
     replacement = REPLACEMENT_DOLLAR_DOLLAR.matcher(replacement).replaceAll(
         REPLACEMENT_DOLLAR_DOLLAR_FOR_JAVA);

     return globalFlag ? pattern.matcher(input).replaceAll(replacement)
         : pattern.matcher(input).replaceFirst(replacement);
   }

   /**
    * Sets the zero-based position at which to start the next match.
    */
   public void setLastIndex(int lastIndex) {
     this.lastIndex = lastIndex;
   }

   /**
    * Splits the input string around matches of the regular expression. If the
    * regular expression is completely empty, splits the input string into its
    * constituent characters. If the regular expression is not empty but matches
    * an empty string, the results are not well defined.
    *
    * @param input the string to be split.
    * @return the strings split off, any of which may be empty.
    */
   public SplitResult split(String input) {
     return split(input, -1);
   }

   /**
    * Splits the input string around matches of the regular expression. If the
    * regular expression is completely empty, splits the input string into its
    * constituent characters. If the regular expression is not empty but matches
    * an empty string, the results are not well defined.
    *
    * Note: There are some browser inconsistencies with this implementation, as
    * it is delegated to the browser, and no browser follows the spec completely.
    * A major difference is that IE will exclude empty strings in the result.
    *
    * @param input the string to be split.
    * @param limit the maximum number of strings to split off and return,
    *        ignoring the rest of the input string. If negative, there is no
    *        limit.
    * @return the strings split off, any of which may be empty.
    */
   public SplitResult split(String input, int limit) {
     String[] result;
     if (source.length() == 0) {
       // Javascript split using a completely empty regular expression splits the
       // string into its constituent characters.
       int resultLength = input.length();
       if (resultLength > limit && limit >= 0) {
         resultLength = limit;
       }
       result = new String[resultLength];
       for (int i = 0; i < resultLength; i++) {
         result[i] = input.substring(i, i + 1);
       }
     } else {
       result = pattern.split(input, limit < 0 ? -1 : (limit + 1));
       if (result.length > limit && limit >= 0) {
         // Chop off the unsplit part of the string which has been put in
         // result[limit]. Javascript split does not return it.
         String[] realResult = new String[limit];
         for (int i = 0; i < limit; i++) {
           realResult[i] = result[i];
         }
         result = realResult;
       }
     }
     return new SplitResult(result);
   }

   /**
    * Determines if the regular expression matches the given string. This call
    * affects the value returned by {@link #getLastIndex()} if the global flag is
    * set. Equivalent to: {@code exec(input) != null}
    *
    * @param input the string to apply the regular expression to
    * @return whether the regular expression matches the given string.
    */
   public boolean test(String input) {
     return exec(input) != null;
   }
 }
	/*
	* Copyright 2010 Google Inc.
	*
	* Licensed under the Apache License, Version 2.0 (the "License"); you may not
	* use this file except in compliance with the License. You may obtain a copy of
	* the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
	* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
	* License for the specific language governing permissions and limitations under
	* the License.
	*/
	package com.google.gwt.regexp.shared;

	import java.util.ArrayList;
	import java.util.HashSet;
	import java.util.List;
	import java.util.Set;
	import java.util.regex.Matcher;
	import java.util.regex.Pattern;

	/**
	* A class for regular expressions with features like Javascript's RegExp, plus
	* Javascript String's replace and split methods (which can take a RegExp
	* parameter). The pure Java implementation (for server-side use) uses Java's
	* Pattern class, unavailable under GWT. The super-sourced GWT implementation
	* simply calls on to the native Javascript classes.
	* <p>
	* There are a few small incompatibilities between the two implementations.
	* Java-specific constructs in the regular expression syntax (e.g. [a-z&&[^bc]],
	* (?<=foo), \A, \Q) work only in the pure Java implementation, not the GWT
	* implementation, and are not rejected by either. Also, the Javascript-specific
	* constructs $` and $' in the replacement expression work only in the GWT
	* implementation, not the pure Java implementation, which rejects them.
	*/
	public class RegExp {

	// In JS syntax, a \ in the replacement string has no special meaning.
	// In Java syntax, a \ in the replacement string escapes the next character,
	// so we have to translate \ to \\ before passing it to Java.
	private static final Pattern REPLACEMENT_BACKSLASH = Pattern.compile("\\\\");
	// To get \\, we have to say \\\\\\\\:
	// \\\\\\\\ --> Java string unescape --> \\\\
	// \\\\ ---> Pattern replacement unescape in replacement preprocessing --> \\
	private static final String REPLACEMENT_BACKSLASH_FOR_JAVA = "\\\\\\\\";

	// In JS syntax, a $& in the replacement string stands for the whole match.
	// In Java syntax, the equivalent is $0, so we have to translate $& to
	// $0 before passing it to Java. However, we have to watch out for $$&, which
	// is actually a Javascript $$ (see below) followed by a & with no special
	// meaning, and must not get translated.
	private static final Pattern REPLACEMENT_DOLLAR_AMPERSAND =
	Pattern.compile("((?:^\|\\G\|[^$])(?:\\$\\$)*)\\$&");
	private static final String REPLACEMENT_DOLLAR_AMPERSAND_FOR_JAVA = "$1\\$0";

	// In JS syntax, a $` and $' in the replacement string stand for everything
	// before the match and everything after the match.
	// In Java syntax, there is no equivalent, so we detect and reject $` and $'.
	// However, we have to watch out for $$` and $$', which are actually a JS $$
	// (see below) followed by a ` or ' with no special meaning, and must not be
	// rejected.
	private static final Pattern REPLACEMENT_DOLLAR_APOSTROPHE =
	Pattern.compile("(?:^\|[^$])(?:\\$\\$)*\\$[`']");

	// In JS syntax, a $$ in the replacement string stands for a (single) dollar
	// sign, $.
	// In Java syntax, the equivalent is \$, so we have to translate $$ to \$
	// before passing it to Java.
	private static final Pattern REPLACEMENT_DOLLAR_DOLLAR =
	Pattern.compile("\\$\\$");
	// To get \$, we have to say \\\\\\$:
	// \\\\\\$ --> Java string unescape --> \\\$
	// \\\$ ---> Pattern replacement unescape in replacement preprocessing --> \$
	private static final String REPLACEMENT_DOLLAR_DOLLAR_FOR_JAVA = "\\\\\\$";

	/**
	* Creates a regular expression object from a pattern with no flags.
	*
	* @param pattern the Javascript regular expression pattern to compile
	* @return a new regular expression
	* @throws RuntimeException if the pattern is invalid
	*/
	public static RegExp compile(String pattern) {
	return compile(pattern, "");
	}

	/**
	* Creates a regular expression object from a pattern using the given flags.
	*
	* @param pattern the Javascript regular expression pattern to compile
	* @param flags the flags string, containing at most one occurrence of {@code
	* 'g'} ({@link #getGlobal()}), {@code 'i'} ({@link #getIgnoreCase()}),
	* or {@code 'm'} ({@link #getMultiline()}).
	* @return a new regular expression
	* @throws RuntimeException if the pattern or the flags are invalid
	*/
	public static RegExp compile(String pattern, String flags) {
	// Parse flags
	boolean globalFlag = false;
	int javaPatternFlags = Pattern.UNIX_LINES;
	for (char flag : parseFlags(flags)) {
	switch (flag) {
	case 'g':
	globalFlag = true;
	break;

	case 'i':
	javaPatternFlags \|= Pattern.CASE_INSENSITIVE \| Pattern.UNICODE_CASE;
	break;

	case 'm':
	javaPatternFlags \|= Pattern.MULTILINE;
	break;

	default:
	throw new IllegalArgumentException("Unknown regexp flag: '" + flag
	+ "'");
	}
	}

	Pattern javaPattern = Pattern.compile(pattern, javaPatternFlags);

	return new RegExp(pattern, javaPattern, globalFlag);
	}

	/**
	* Parses a flags string as a set of characters. Does not reject unknown
	* flags.
	*
	* @param flags the flag string to parse
	* @return a set of flags
	* @throws IllegalArgumentException if a flag is duplicated
	*/
	private static Set<Character> parseFlags(String flags) {
	Set<Character> flagsSet = new HashSet<Character>(flags.length());
	for (int flagIndex = 0; flagIndex < flags.length(); flagIndex++) {
	char flag = flags.charAt(flagIndex);
	if (!flagsSet.add(flag)) {
	throw new IllegalArgumentException("Flag cannot be specified twice: '"
	+ flag + "'");
	}
	}
	return flagsSet;
	}

	private final boolean globalFlag;

	private int lastIndex;

	private final Pattern pattern;

	private final String source;

	private RegExp(String source, Pattern pattern, boolean globalFlag) {
	this.source = source;
	this.pattern = pattern;
	this.globalFlag = globalFlag;
	lastIndex = 0;
	}

	/**
	* Applies the regular expression to the given string. This call affects the
	* value returned by {@link #getLastIndex()} if the global flag is set.
	*
	* @param input the string to apply the regular expression to
	* @return a match result if the string matches, else {@code null}
	*/
	public MatchResult exec(String input) {
	// Start the search at lastIndex if the global flag is true.
	int searchStartIndex = (globalFlag) ? lastIndex : 0;

	Matcher matcher;
	if (input == null \|\| searchStartIndex < 0
	\|\| searchStartIndex > input.length()) {
	// Avoid exceptions: Javascript is more tolerant than Java
	matcher = null;
	} else {
	matcher = pattern.matcher(input);
	if (!matcher.find(searchStartIndex)) {
	matcher = null;
	}
	}

	if (matcher != null) {
	// Match: create a result

	// Retrieve the matched groups.
	int groupCount = matcher.groupCount();
	List<String> groups = new ArrayList<String>(1 + groupCount);
	for (int group = 0; group <= groupCount; group++) {
	groups.add(matcher.group(group));
	}

	if (globalFlag) {
	lastIndex = matcher.end();
	}

	return new MatchResult(matcher.start(), input, groups);
	} else {
	// No match
	if (globalFlag) {
	lastIndex = 0;
	}
	return null;
	}
	}

	/**
	* Returns whether the regular expression captures all occurrences of the
	* pattern.
	*/
	public boolean getGlobal() {
	return globalFlag;
	}

	/**
	* Returns whether the regular expression ignores case.
	*/
	public boolean getIgnoreCase() {
	return (pattern.flags() & Pattern.CASE_INSENSITIVE) != 0;
	}

	/**
	* Returns the zero-based position at which to start the next match. The
	* return value is not defined if the global flag is not set. After a call
	* to {@link #exec(String)} or {@link #test(String)}, this method returns
	* the next position following the most recent match.
	*
	* @see #getGlobal()
	*/
	public int getLastIndex() {
	return lastIndex;
	}

	/**
	* Returns whether '$' and '^' match line returns ('\n' and '\r') in addition
	* to the beginning or end of the string.
	*/
	public boolean getMultiline() {
	return (pattern.flags() & Pattern.MULTILINE) != 0;
	}

	/**
	* Returns the pattern string of the regular expression.
	*/
	public String getSource() {
	return source;
	}

	/**
	* Returns the input string with the part(s) matching the regular expression
	* replaced with the replacement string. If the global flag is set, replaces
	* all matches of the regular expression. Otherwise, replaces the first match
	* of the regular expression. As per Javascript semantics, backslashes in the
	* replacement string get no special treatment, but the replacement string can
	* use the following special patterns:
	* <ul>
	* <li>$1, $2, ... $99 - inserts the n'th group matched by the regular
	* expression.
	* <li>$& - inserts the entire string matched by the regular expression.
	* <li>$$ - inserts a $.
	* </ul>
	* Note: $` and $' are not supported in the pure Java implementation, and
	* throw an exception.
	*
	* @param input the string in which the regular expression is to be searched.
	* @param replacement the replacement string.
	* @return the input string with the regular expression replaced by the
	* replacement string.
	* @throws RuntimeException if {@code replacement} is invalid
	*/
	public String replace(String input, String replacement) {
	// Replace \ in the replacement with \\ to escape it for Java replace.
	replacement = REPLACEMENT_BACKSLASH.matcher(replacement).replaceAll(
	REPLACEMENT_BACKSLASH_FOR_JAVA);

	// Replace the Javascript-ese $& in the replacement with Java-ese $0, but
	// watch out for $$&, which should stay $$&, to be changed to \$& below.
	replacement = REPLACEMENT_DOLLAR_AMPERSAND.matcher(replacement).replaceAll(
	REPLACEMENT_DOLLAR_AMPERSAND_FOR_JAVA);

	// Test for Javascript-ese $` and $', which we do not support in the pure
	// Java version.
	if (REPLACEMENT_DOLLAR_APOSTROPHE.matcher(replacement).find()) {
	throw new UnsupportedOperationException(
	"$` and $' replacements are not supported");
	}

	// Replace the Javascript-ese $$ in the replacement with Java-ese \$.
	replacement = REPLACEMENT_DOLLAR_DOLLAR.matcher(replacement).replaceAll(
	REPLACEMENT_DOLLAR_DOLLAR_FOR_JAVA);

	return globalFlag ? pattern.matcher(input).replaceAll(replacement)
	: pattern.matcher(input).replaceFirst(replacement);
	}

	/**
	* Sets the zero-based position at which to start the next match.
	*/
	public void setLastIndex(int lastIndex) {
	this.lastIndex = lastIndex;
	}

	/**
	* Splits the input string around matches of the regular expression. If the
	* regular expression is completely empty, splits the input string into its
	* constituent characters. If the regular expression is not empty but matches
	* an empty string, the results are not well defined.
	*
	* @param input the string to be split.
	* @return the strings split off, any of which may be empty.
	*/
	public SplitResult split(String input) {
	return split(input, -1);
	}

	/**
	* Splits the input string around matches of the regular expression. If the
	* regular expression is completely empty, splits the input string into its
	* constituent characters. If the regular expression is not empty but matches
	* an empty string, the results are not well defined.
	*
	* Note: There are some browser inconsistencies with this implementation, as
	* it is delegated to the browser, and no browser follows the spec completely.
	* A major difference is that IE will exclude empty strings in the result.
	*
	* @param input the string to be split.
	* @param limit the maximum number of strings to split off and return,
	* ignoring the rest of the input string. If negative, there is no
	* limit.
	* @return the strings split off, any of which may be empty.
	*/
	public SplitResult split(String input, int limit) {
	String[] result;
	if (source.length() == 0) {
	// Javascript split using a completely empty regular expression splits the
	// string into its constituent characters.
	int resultLength = input.length();
	if (resultLength > limit && limit >= 0) {
	resultLength = limit;
	}
	result = new String[resultLength];
	for (int i = 0; i < resultLength; i++) {
	result[i] = input.substring(i, i + 1);
	}
	} else {
	result = pattern.split(input, limit < 0 ? -1 : (limit + 1));
	if (result.length > limit && limit >= 0) {
	// Chop off the unsplit part of the string which has been put in
	// result[limit]. Javascript split does not return it.
	String[] realResult = new String[limit];
	for (int i = 0; i < limit; i++) {
	realResult[i] = result[i];
	}
	result = realResult;
	}
	}
	return new SplitResult(result);
	}

	/**
	* Determines if the regular expression matches the given string. This call
	* affects the value returned by {@link #getLastIndex()} if the global flag is
	* set. Equivalent to: {@code exec(input) != null}
	*
	* @param input the string to apply the regular expression to
	* @return whether the regular expression matches the given string.
	*/
	public boolean test(String input) {
	return exec(input) != null;
	}
	}