1 /* 2 [The "BSD license"] 3 Copyright (c) 2005-2009 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 */ 28 package org.antlr.runtime; 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 public interface IntStream { 34 void 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 int LA(int 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 int 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 int 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 void rewind(int marker); 67 68 /** Rewind to the input position of the last marker. 69 * Used currently only after a cyclic DFA and just 70 * before starting a sem/syn predicate to get the 71 * input position back to the start of the decision. 72 * Do not "pop" the marker off the state. mark(i) 73 * and rewind(i) should balance still. It is 74 * like invoking rewind(last marker) but it should not "pop" 75 * the marker off. It's like seek(last marker's input position). 76 */ 77 void rewind(); 78 79 /** You may want to commit to a backtrack but don't want to force the 80 * stream to keep bookkeeping objects around for a marker that is 81 * no longer necessary. This will have the same behavior as 82 * rewind() except it releases resources without the backward seek. 83 * This must throw away resources for all markers back to the marker 84 * argument. So if you're nested 5 levels of mark(), and then release(2) 85 * you have to release resources for depths 2..5. 86 */ 87 void release(int marker); 88 89 /** Set the input cursor to the position indicated by index. This is 90 * normally used to seek ahead in the input stream. No buffering is 91 * required to do this unless you know your stream will use seek to 92 * move backwards such as when backtracking. 93 * 94 * This is different from rewind in its multi-directional 95 * requirement and in that its argument is strictly an input cursor (index). 96 * 97 * For char streams, seeking forward must update the stream state such 98 * as line number. For seeking backwards, you will be presumably 99 * backtracking using the mark/rewind mechanism that restores state and 100 * so this method does not need to update state when seeking backwards. 101 * 102 * Currently, this method is only used for efficient backtracking using 103 * memoization, but in the future it may be used for incremental parsing. 104 * 105 * The index is 0..n-1. A seek to position i means that LA(1) will 106 * return the ith symbol. So, seeking to 0 means LA(1) will return the 107 * first element in the stream. 108 */ 109 void seek(int index); 110 111 /** Only makes sense for streams that buffer everything up probably, but 112 * might be useful to display the entire stream or for testing. This 113 * value includes a single EOF. 114 */ 115 int size(); 116 117 /** Where are you getting symbols from? Normally, implementations will 118 * pass the buck all the way to the lexer who can ask its input stream 119 * for the file name or whatever. 120 */ 121 public String getSourceName(); 122 } 123
