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   1  <?php
   2  /*
   3   [The "BSD licence"]
   4   Copyright (c) 2005-2008 Terence Parr
   5   All rights reserved.
   6  
   7   Redistribution and use in source and binary forms, with or without
   8   modification, are permitted provided that the following conditions
   9   are met:
  10   1. Redistributions of source code must retain the above copyright
  11      notice, this list of conditions and the following disclaimer.
  12   2. Redistributions in binary form must reproduce the above copyright
  13      notice, this list of conditions and the following disclaimer in the
  14      documentation and/or other materials provided with the distribution.
  15   3. The name of the author may not be used to endorse or promote products
  16      derived from this software without specific prior written permission.
  17  
  18   THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  19   IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  20   OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  21   IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  22   INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  23   NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  24   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  25   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  26   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  27   THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  28  */
  29  
  30  /** A simple stream of integers used when all I care about is the char
  31   *  or token type sequence (such as interpretation).
  32   */
  33  interface IntStream {
  34  	function consume();
  35  
  36      /** Get int at current input pointer + i ahead where i=1 is next int.
  37       *  Negative indexes are allowed.  LA(-1) is previous token (token
  38       *  just matched).  LA(-i) where i is before first token should
  39       *  yield -1, invalid char / EOF.
  40       */
  41      function LA($i);
  42  
  43      /** Tell the stream to start buffering if it hasn't already.  Return
  44       *  current input position, index(), or some other marker so that
  45       *  when passed to rewind() you get back to the same spot.
  46       *  rewind(mark()) should not affect the input cursor.  The Lexer
  47       *  track line/col info as well as input index so its markers are
  48       *  not pure input indexes.  Same for tree node streams.
  49       */
  50  	function mark();
  51  
  52      /** Return the current input symbol index 0..n where n indicates the
  53       *  last symbol has been read.  The index is the symbol about to be
  54       *  read not the most recently read symbol.
  55       */
  56  	function index();
  57  
  58      /** Reset the stream so that next call to index would return marker.
  59       *  The marker will usually be index() but it doesn't have to be.  It's
  60       *  just a marker to indicate what state the stream was in.  This is
  61       *  essentially calling release() and seek().  If there are markers
  62       *  created after this marker argument, this routine must unroll them
  63       *  like a stack.  Assume the state the stream was in when this marker
  64       *  was created.
  65       */
  66  	function rewind($marker=null);
  67  
  68      /** You may want to commit to a backtrack but don't want to force the
  69       *  stream to keep bookkeeping objects around for a marker that is
  70       *  no longer necessary.  This will have the same behavior as
  71       *  rewind() except it releases resources without the backward seek.
  72       *  This must throw away resources for all markers back to the marker
  73       *  argument.  So if you're nested 5 levels of mark(), and then release(2)
  74       *  you have to release resources for depths 2..5.
  75       */
  76  	function release($marker);
  77  
  78      /** Set the input cursor to the position indicated by index.  This is
  79       *  normally used to seek ahead in the input stream.  No buffering is
  80       *  required to do this unless you know your stream will use seek to
  81       *  move backwards such as when backtracking.
  82       *
  83       *  This is different from rewind in its multi-directional
  84       *  requirement and in that its argument is strictly an input cursor (index).
  85       *
  86       *  For char streams, seeking forward must update the stream state such
  87       *  as line number.  For seeking backwards, you will be presumably
  88       *  backtracking using the mark/rewind mechanism that restores state and
  89       *  so this method does not need to update state when seeking backwards.
  90       *
  91       *  Currently, this method is only used for efficient backtracking using
  92       *  memoization, but in the future it may be used for incremental parsing.
  93       *
  94       *  The index is 0..n-1.  A seek to position i means that LA(1) will
  95       *  return the ith symbol.  So, seeking to 0 means LA(1) will return the
  96       *  first element in the stream. 
  97       */
  98  	function seek($index);
  99  
 100      /** Only makes sense for streams that buffer everything up probably, but
 101       *  might be useful to display the entire stream or for testing.  This
 102       *  value includes a single EOF.
 103       */
 104  	function size();
 105  
 106      /** Where are you getting symbols from?  Normally, implementations will
 107       *  pass the buck all the way to the lexer who can ask its input stream
 108       *  for the file name or whatever.
 109       */
 110  	public function getSourceName();
 111  }
 112  ?>