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/* gnu/regexp/RETokenWordBoundary.java

   Copyright (C) 2006 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify

it under the terms of the GNU General Public License as published by

the Free Software Foundation; either version 2, or (at your option)

any later version.

GNU Classpath is distributed in the hope that it will be useful, but

WITHOUT ANY WARRANTY; without even the implied warranty of

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

General Public License for more details.

You should have received a copy of the GNU General Public License

along with GNU Classpath; see the file COPYING.  If not, write to the

Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

02110-1301 USA.

Linking this library statically or dynamically with other modules is

making a combined work based on this library.  Thus, the terms and

conditions of the GNU General Public License cover the whole

combination.

As a special exception, the copyright holders of this library give you

permission to link this library with independent modules to produce an

executable, regardless of the license terms of these independent

modules, and to copy and distribute the resulting executable under

terms of your choice, provided that you also meet, for each linked

independent module, the terms and conditions of the license of that

module.  An independent module is a module which is not derived from

or based on this library.  If you modify this library, you may extend

this exception to your version of the library, but you are not

obligated to do so.  If you do not wish to do so, delete this

exception statement from your version. */

package gnu.java.util.regex;

import gnu.java.lang.CPStringBuilder;

/**

 * Represents a combination lookahead/lookbehind for POSIX [:alnum:].

 */

final class RETokenWordBoundary extends REToken

{

  private boolean negated;

  private int where;

  static final int BEGIN = 1;

  static final int END = 2;

    RETokenWordBoundary (int subIndex, int where, boolean negated)

  {

    super (subIndex);

    this.where = where;

    this.negated = negated;

  }

  int getMaximumLength ()

  {

    return 0;

  }

  REMatch matchThis (CharIndexed input, REMatch mymatch)

  {

    // Word boundary means input[index-1] was a word character

    // and input[index] is not, or input[index] is a word character

    // and input[index-1] was not

    //  In the string "one two three", these positions match:

    //  |o|n|e| |t|w|o| |t|h|r|e|e|

    //  ^     ^ ^     ^ ^         ^

    boolean after = false;      // is current character a letter or digit?

    boolean before = false;     // is previous character a letter or digit?

    char ch;

    // TODO: Also check REG_ANCHORINDEX vs. anchor

    if (((mymatch.eflags & RE.REG_ANCHORINDEX) != RE.REG_ANCHORINDEX)

        || (mymatch.offset + mymatch.index > mymatch.anchor))

      {

        if ((ch =

             input.charAt (mymatch.index - 1)) != CharIndexed.OUT_OF_BOUNDS)

          {

            before = Character.isLetterOrDigit (ch) || (ch == '_');

          }

      }

    if ((ch = input.charAt (mymatch.index)) != CharIndexed.OUT_OF_BOUNDS)

      {

        after = Character.isLetterOrDigit (ch) || (ch == '_');

      }

    // if (before) and (!after), we're at end (\>)

    // if (after) and (!before), we're at beginning (\<)

    boolean doNext = false;

    if ((where & BEGIN) == BEGIN)

      {

        doNext = after && !before;

      }

    if ((where & END) == END)

      {

        doNext ^= before && !after;

      }

    if (negated)

      doNext = !doNext;

    return (doNext ? mymatch : null);

  }

  boolean returnsFixedLengthMatches ()

  {

    return true;

  }

  int findFixedLengthMatches (CharIndexed input, REMatch mymatch, int max)

  {

    if (matchThis (input, mymatch) != null)

      return max;

    else

      return 0;

  }

  void dump (CPStringBuilder os)

  {

    if (where == (BEGIN | END))

      {

        os.append (negated ? "\\B" : "\\b");

      }

    else if (where == BEGIN)

      {

        os.append ("\\<");

      }

    else

      {

        os.append ("\\>");

      }

  }

}