Source for gnu.regexp.CharIndexed

   1: /* gnu/regexp/CharIndexed.java
   2:    Copyright (C) 1998-2001, 2004, 2006 Free Software Foundation, Inc.
   3: 
   4: This file is part of GNU Classpath.
   5: 
   6: GNU Classpath is free software; you can redistribute it and/or modify
   7: it under the terms of the GNU General Public License as published by
   8: the Free Software Foundation; either version 2, or (at your option)
   9: any later version.
  10: 
  11: GNU Classpath is distributed in the hope that it will be useful, but
  12: WITHOUT ANY WARRANTY; without even the implied warranty of
  13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14: General Public License for more details.
  15: 
  16: You should have received a copy of the GNU General Public License
  17: along with GNU Classpath; see the file COPYING.  If not, write to the
  18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19: 02110-1301 USA.
  20: 
  21: Linking this library statically or dynamically with other modules is
  22: making a combined work based on this library.  Thus, the terms and
  23: conditions of the GNU General Public License cover the whole
  24: combination.
  25: 
  26: As a special exception, the copyright holders of this library give you
  27: permission to link this library with independent modules to produce an
  28: executable, regardless of the license terms of these independent
  29: modules, and to copy and distribute the resulting executable under
  30: terms of your choice, provided that you also meet, for each linked
  31: independent module, the terms and conditions of the license of that
  32: module.  An independent module is a module which is not derived from
  33: or based on this library.  If you modify this library, you may extend
  34: this exception to your version of the library, but you are not
  35: obligated to do so.  If you do not wish to do so, delete this
  36: exception statement from your version. */
  37: 
  38: package gnu.regexp;
  39: 
  40: /**
  41:  * Defines the interface used internally so that different types of source
  42:  * text can be accessed in the same way.  Built-in concrete classes provide
  43:  * support for String, StringBuffer, InputStream and char[] types.
  44:  * A class that is CharIndexed supports the notion of a cursor within a
  45:  * block of text.  The cursor must be able to be advanced via the move()
  46:  * method.  The charAt() method returns the character at the cursor position
  47:  * plus a given offset.
  48:  *
  49:  * @author <A HREF="mailto:wes@cacas.org">Wes Biggs</A>
  50:  */
  51: public interface CharIndexed {
  52:     /**
  53:      * Defines a constant (0xFFFF was somewhat arbitrarily chosen)
  54:      * that can be returned by the charAt() function indicating that
  55:      * the specified index is out of range.
  56:      */
  57:     char OUT_OF_BOUNDS = '\uFFFF';
  58: 
  59:     /**
  60:      * Returns the character at the given offset past the current cursor
  61:      * position in the input.  The index of the current position is zero.
  62:      * It is possible for this method to be called with a negative index.
  63:      * This happens when using the '^' operator in multiline matching mode
  64:      * or the '\b' or '\<' word boundary operators.  In any case, the lower
  65:      * bound is currently fixed at -2 (for '^' with a two-character newline).
  66:      *
  67:      * @param index the offset position in the character field to examine
  68:      * @return the character at the specified index, or the OUT_OF_BOUNDS
  69:      *   character defined by this interface.
  70:      */
  71:     char charAt(int index);
  72: 
  73:     /**
  74:      * Shifts the input buffer by a given number of positions.  Returns
  75:      * true if the new cursor position is valid.
  76:      */
  77:     boolean move(int index);
  78: 
  79:     /**
  80:      * Returns true if the most recent move() operation placed the cursor
  81:      * position at a valid position in the input.
  82:      */
  83:     boolean isValid();
  84: 
  85:     /**
  86:      * Returns another CharIndexed containing length characters to the left
  87:      * of the given index. The given length is an expected maximum and
  88:      * the returned CharIndexed may not necessarily contain so many characters.
  89:      */
  90:     CharIndexed lookBehind(int index, int length);
  91: 
  92:     /**
  93:      * Returns the effective length of this CharIndexed
  94:      */
  95:     int length();
  96: }