1 /* 2 [The "BSD licence"] 3 Copyright (c) 2007-2008 Johannes Luber 4 Copyright (c) 2005-2007 Kunle Odutola 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 14 the documentation and/or other materials provided with the 15 distribution. 16 3. The name of the author may not be used to endorse or promote products 17 derived from this software without specific prior WRITTEN permission. 18 4. Unless explicitly state otherwise, any contribution intentionally 19 submitted for inclusion in this work to the copyright owner or licensor 20 shall be under the terms and conditions of this license, without any 21 additional terms or conditions. 22 23 THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 24 IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 25 OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 26 IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 27 INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 28 NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 29 DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 30 THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 31 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 32 THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 33 */ 34 35 36 namespace Antlr.Runtime 37 { 38 using System; 39 40 /// <summary> 41 /// A simple stream of integers. This is useful when all we care about is the char 42 /// or token type sequence (such as for interpretation). 43 /// </summary> 44 public interface IIntStream 45 { Consume()46 void Consume(); 47 48 /// <summary> 49 /// Get int at current input pointer + i ahead (where i=1 is next int) 50 /// Negative indexes are allowed. LA(-1) is previous token (token just matched). 51 /// LA(-i) where i is before first token should yield -1, invalid char or EOF. 52 /// </summary> LA(int i)53 int LA(int i); 54 55 /// <summary>Tell the stream to start buffering if it hasn't already.</summary> 56 /// <remarks> 57 /// Executing Rewind(Mark()) on a stream should not affect the input position. 58 /// The Lexer tracks line/col info as well as input index so its markers are 59 /// not pure input indexes. Same for tree node streams. */ 60 /// </remarks> 61 /// <returns>Return a marker that can be passed to 62 /// <see cref="IIntStream.Rewind(int)"/> to return to the current position. 63 /// This could be the current input position, a value return from 64 /// <see cref="IIntStream.Index"/>, or some other marker.</returns> Mark()65 int Mark(); 66 67 /// <summary> 68 /// Return the current input symbol index 0..n where n indicates the 69 /// last symbol has been read. The index is the symbol about to be 70 /// read not the most recently read symbol. 71 /// </summary> 72 int Index { get; } 73 74 /// <summary> 75 /// Resets the stream so that the next call to 76 /// <see cref="IIntStream.Index"/> would return marker. 77 /// </summary> 78 /// <remarks> 79 /// The marker will usually be <see cref="IIntStream.Index"/> but 80 /// it doesn't have to be. It's just a marker to indicate what 81 /// state the stream was in. This is essentially calling 82 /// <see cref="IIntStream.Release"/> and <see cref="IIntStream.Seek"/>. 83 /// If there are other markers created after the specified marker, 84 /// this routine must unroll them like a stack. Assumes the state the 85 /// stream was in when this marker was created. 86 /// </remarks> Rewind(int marker)87 void Rewind(int marker); 88 89 /// <summary> 90 /// Rewind to the input position of the last marker. 91 /// </summary> 92 /// <remarks> 93 /// Used currently only after a cyclic DFA and just before starting 94 /// a sem/syn predicate to get the input position back to the start 95 /// of the decision. Do not "pop" the marker off the state. Mark(i) 96 /// and Rewind(i) should balance still. It is like invoking 97 /// Rewind(last marker) but it should not "pop" the marker off. 98 /// It's like Seek(last marker's input position). 99 /// </remarks> Rewind()100 void Rewind(); 101 102 /// <summary> 103 /// You may want to commit to a backtrack but don't want to force the 104 /// stream to keep bookkeeping objects around for a marker that is 105 /// no longer necessary. This will have the same behavior as 106 /// <see cref="IIntStream.Rewind(int)"/> except it releases resources without 107 /// the backward seek. 108 /// </summary> 109 /// <remarks> 110 /// This must throw away resources for all markers back to the marker 111 /// argument. So if you're nested 5 levels of Mark(), and then Release(2) 112 /// you have to release resources for depths 2..5. 113 /// </remarks> Release(int marker)114 void Release(int marker); 115 116 /// <summary> 117 /// Set the input cursor to the position indicated by index. This is 118 /// normally used to seek ahead in the input stream. 119 /// </summary> 120 /// <remarks> 121 /// No buffering is required to do this unless you know your stream 122 /// will use seek to move backwards such as when backtracking. 123 /// 124 /// This is different from rewind in its multi-directional requirement 125 /// and in that its argument is strictly an input cursor (index). 126 /// 127 /// For char streams, seeking forward must update the stream state such 128 /// as line number. For seeking backwards, you will be presumably 129 /// backtracking using the 130 /// <see cref="IIntStream.Mark"/>/<see cref="IIntStream.Rewind(int)"/> 131 /// mechanism that restores state and so this method does not need to 132 /// update state when seeking backwards. 133 /// 134 /// Currently, this method is only used for efficient backtracking using 135 /// memoization, but in the future it may be used for incremental parsing. 136 /// 137 /// The index is 0..n-1. A seek to position i means that LA(1) will return 138 /// the ith symbol. So, seeking to 0 means LA(1) will return the first 139 /// element in the stream. 140 /// </remarks> Seek(int index)141 void Seek(int index); 142 143 /// <summary>Returns the size of the entire stream.</summary> 144 /// <remarks> 145 /// Only makes sense for streams that buffer everything up probably, 146 /// but might be useful to display the entire stream or for testing. 147 /// This value includes a single EOF. 148 /// </remarks> 149 int Count { get; } 150 151 /// <summary> 152 /// Where are you getting symbols from? Normally, implementations will 153 /// pass the buck all the way to the lexer who can ask its input stream 154 /// for the file name or whatever. 155 /// </summary> 156 string SourceName { 157 get; 158 } 159 } 160 }