1/*
2 [The "BSD licence"]
3 Copyright (c) 2005-2006 Terence Parr
4 All rights reserved.
5
6 Redistribution and use in source and binary forms, with or without
7 modification, are permitted provided that the following conditions
8 are met:
9 1. Redistributions of source code must retain the above copyright
10    notice, this list of conditions and the following disclaimer.
11 2. Redistributions in binary form must reproduce the above copyright
12    notice, this list of conditions and the following disclaimer in the
13    documentation and/or other materials provided with the distribution.
14 3. The name of the author may not be used to endorse or promote products
15    derived from this software without specific prior written permission.
16
17 THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18 IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19 OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20 IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21 INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22 NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27*/
28package org.antlr.runtime {
29	/** A simple stream of integers used when all I care about is the char
30	 *  or token type sequence (such as interpretation).
31	 */
32	public interface IntStream {
33		function consume():void;
34
35		/** Get int at current input pointer + i ahead where i=1 is next int.
36		 *  Negative indexes are allowed.  LA(-1) is previous token (token
37		 *  just matched).  LA(-i) where i is before first token should
38		 *  yield -1, invalid char / EOF.
39		 */
40		function LA(i:int):int;
41
42		/** Tell the stream to start buffering if it hasn't already.  Return
43	     *  current input position, index(), or some other marker so that
44		 *  when passed to rewind() you get back to the same spot.
45		 *  rewind(mark()) should not affect the input cursor.  The Lexer
46		 *  track line/col info as well as input index so its markers are
47		 *  not pure input indexes.  Same for tree node streams.
48	     */
49		function mark():int;
50
51		/** Return the current input symbol index 0..n where n indicates the
52	     *  last symbol has been read.  The index is the symbol about to be
53		 *  read not the most recently read symbol.
54	     */
55		function get index():int;
56
57		/** Reset the stream so that next call to index would return marker.
58		 *  The marker will usually be index() but it doesn't have to be.  It's
59		 *  just a marker to indicate what state the stream was in.  This is
60		 *  essentially calling release() and seek().  If there are markers
61		 *  created after this marker argument, this routine must unroll them
62		 *  like a stack.  Assume the state the stream was in when this marker
63		 *  was created.
64		 */
65		function rewindTo(marker:int):void;
66
67		/** Rewind to the input position of the last marker.
68		 *  Used currently only after a cyclic DFA and just
69		 *  before starting a sem/syn predicate to get the
70		 *  input position back to the start of the decision.
71		 *  Do not "pop" the marker off the state.  mark(i)
72		 *  and rewind(i) should balance still. It is
73		 *  like invoking rewind(last marker) but it should not "pop"
74		 *  the marker off.  It's like seek(last marker's input position).
75		 */
76		function rewind():void;
77
78		/** You may want to commit to a backtrack but don't want to force the
79		 *  stream to keep bookkeeping objects around for a marker that is
80		 *  no longer necessary.  This will have the same behavior as
81		 *  rewind() except it releases resources without the backward seek.
82		 *  This must throw away resources for all markers back to the marker
83		 *  argument.  So if you're nested 5 levels of mark(), and then release(2)
84		 *  you have to release resources for depths 2..5.
85		 */
86		function release(marker:int):void;
87
88		/** Set the input cursor to the position indicated by index.  This is
89		 *  normally used to seek ahead in the input stream.  No buffering is
90		 *  required to do this unless you know your stream will use seek to
91		 *  move backwards such as when backtracking.
92		 *
93		 *  This is different from rewind in its multi-directional
94		 *  requirement and in that its argument is strictly an input cursor (index).
95		 *
96		 *  For char streams, seeking forward must update the stream state such
97		 *  as line number.  For seeking backwards, you will be presumably
98		 *  backtracking using the mark/rewind mechanism that restores state and
99		 *  so this method does not need to update state when seeking backwards.
100		 *
101		 *  Currently, this method is only used for efficient backtracking using
102		 *  memoization, but in the future it may be used for incremental parsing.
103		 *
104		 *  The index is 0..n-1.  A seek to position i means that LA(1) will
105		 *  return the ith symbol.  So, seeking to 0 means LA(1) will return the
106		 *  first element in the stream.
107		 */
108		function seek(index:int):void;
109
110		/** Only makes sense for streams that buffer everything up probably, but
111		 *  might be useful to display the entire stream or for testing.  This
112		 *  value includes a single EOF.
113		 */
114		function get size():int;
115
116		/** Where are you getting symbols from?  Normally, implementations will
117		 *  pass the buck all the way to the lexer who can ask its input stream
118		 *  for the file name or whatever.
119		 */
120		function get sourceName():String;
121	}
122}