[1] | 1 | using System; |
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| 2 | |
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| 3 | namespace antlr |
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| 4 | { |
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| 5 | /*ANTLR Translator Generator |
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| 6 | * Project led by Terence Parr at http://www.jGuru.com |
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| 7 | * Software rights: http://www.antlr.org/license.html |
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| 8 | * |
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| 9 | * $Id:$ |
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| 10 | */ |
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| 11 | |
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| 12 | // |
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| 13 | // ANTLR C# Code Generator by Micheal Jordan |
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| 14 | // Kunle Odutola : kunle UNDERSCORE odutola AT hotmail DOT com |
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| 15 | // Anthony Oguntimehin |
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| 16 | // |
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| 17 | // With many thanks to Eric V. Smith from the ANTLR list. |
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| 18 | // |
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| 19 | |
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| 20 | /*A Stream of Token objects fed to the parser from a Tokenizer that can |
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| 21 | * be rewound via mark()/rewind() methods. |
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| 22 | * <p> |
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| 23 | * A dynamic array is used to buffer up all the input tokens. Normally, |
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| 24 | * "k" tokens are stored in the buffer. More tokens may be stored during |
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| 25 | * guess mode (testing syntactic predicate), or when LT(i>k) is referenced. |
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| 26 | * Consumption of tokens is deferred. In other words, reading the next |
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| 27 | * token is not done by conume(), but deferred until needed by LA or LT. |
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| 28 | * <p> |
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| 29 | * |
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| 30 | * @see antlr.Token |
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| 31 | * @see antlr.Tokenizer |
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| 32 | * @see antlr.TokenQueue |
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| 33 | */ |
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| 34 | |
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| 35 | public class TokenBuffer |
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| 36 | { |
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| 37 | |
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| 38 | // Token source |
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| 39 | protected internal TokenStream input; |
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| 40 | |
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| 41 | // Number of active markers |
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| 42 | protected internal int nMarkers = 0; |
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| 43 | |
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| 44 | // Additional offset used when markers are active |
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| 45 | protected internal int markerOffset = 0; |
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| 46 | |
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| 47 | // Number of calls to consume() since last LA() or LT() call |
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| 48 | protected internal int numToConsume = 0; |
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| 49 | |
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| 50 | // Circular queue |
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| 51 | internal TokenQueue queue; |
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| 52 | |
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| 53 | /*Create a token buffer */ |
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| 54 | public TokenBuffer(TokenStream input_) |
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| 55 | { |
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| 56 | input = input_; |
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| 57 | queue = new TokenQueue(1); |
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| 58 | } |
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| 59 | |
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| 60 | /*Reset the input buffer to empty state */ |
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| 61 | public virtual void reset() |
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| 62 | { |
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| 63 | nMarkers = 0; |
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| 64 | markerOffset = 0; |
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| 65 | numToConsume = 0; |
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| 66 | queue.reset(); |
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| 67 | } |
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| 68 | |
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| 69 | /*Mark another token for deferred consumption */ |
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| 70 | public virtual void consume() |
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| 71 | { |
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| 72 | numToConsume++; |
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| 73 | } |
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| 74 | |
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| 75 | /*Ensure that the token buffer is sufficiently full */ |
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| 76 | protected virtual void fill(int amount) |
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| 77 | { |
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| 78 | syncConsume(); |
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| 79 | // Fill the buffer sufficiently to hold needed tokens |
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| 80 | while (queue.nbrEntries < (amount + markerOffset)) |
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| 81 | { |
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| 82 | // Append the next token |
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| 83 | queue.append(input.nextToken()); |
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| 84 | } |
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| 85 | } |
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| 86 | |
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| 87 | /*return the Tokenizer (needed by ParseView) */ |
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| 88 | public virtual TokenStream getInput() |
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| 89 | { |
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| 90 | return input; |
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| 91 | } |
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| 92 | |
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| 93 | /*Get a lookahead token value */ |
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| 94 | public virtual int LA(int i) |
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| 95 | { |
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| 96 | fill(i); |
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| 97 | return queue.elementAt(markerOffset + i - 1).Type; |
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| 98 | } |
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| 99 | |
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| 100 | /*Get a lookahead token */ |
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| 101 | public virtual IToken LT(int i) |
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| 102 | { |
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| 103 | fill(i); |
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| 104 | return queue.elementAt(markerOffset + i - 1); |
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| 105 | } |
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| 106 | |
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| 107 | /*Return an integer marker that can be used to rewind the buffer to |
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| 108 | * its current state. |
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| 109 | */ |
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| 110 | public virtual int mark() |
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| 111 | { |
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| 112 | syncConsume(); |
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| 113 | nMarkers++; |
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| 114 | return markerOffset; |
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| 115 | } |
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| 116 | |
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| 117 | /*Rewind the token buffer to a marker. |
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| 118 | * @param mark Marker returned previously from mark() |
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| 119 | */ |
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| 120 | public virtual void rewind(int mark) |
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| 121 | { |
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| 122 | syncConsume(); |
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| 123 | markerOffset = mark; |
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| 124 | nMarkers--; |
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| 125 | } |
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| 126 | |
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| 127 | /*Sync up deferred consumption */ |
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| 128 | protected virtual void syncConsume() |
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| 129 | { |
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| 130 | while (numToConsume > 0) |
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| 131 | { |
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| 132 | if (nMarkers > 0) |
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| 133 | { |
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| 134 | // guess mode -- leave leading tokens and bump offset. |
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| 135 | markerOffset++; |
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| 136 | } |
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| 137 | else |
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| 138 | { |
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| 139 | // normal mode -- remove first token |
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| 140 | queue.removeFirst(); |
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| 141 | } |
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| 142 | numToConsume--; |
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| 143 | } |
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| 144 | } |
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| 145 | } |
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| 146 | } |
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