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/* ANTLR Translator Generator |
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* Project led by Terence Parr at http://www.jGuru.com |
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* Software rights: http://www.antlr.org/license.html |
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* |
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* $Id: TokenBuffer.cpp,v 1.1 2005-12-02 15:38:02 tim Exp $ |
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*/ |
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|
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#include "antlr/TokenBuffer.hpp" |
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|
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#ifdef ANTLR_CXX_SUPPORTS_NAMESPACE |
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namespace antlr { |
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#endif |
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|
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/**A Stream of Token objects fed to the parser from a TokenStream that can |
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* be rewound via mark()/rewind() methods. |
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* <p> |
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* A dynamic array is used to buffer up all the input tokens. Normally, |
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* "k" tokens are stored in the buffer. More tokens may be stored during |
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* guess mode (testing syntactic predicate), or when LT(i>k) is referenced. |
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* Consumption of tokens is deferred. In other words, reading the next |
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* token is not done by conume(), but deferred until needed by LA or LT. |
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* <p> |
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* |
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* @see antlr.Token |
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* @see antlr.TokenStream |
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* @see antlr.TokenQueue |
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*/ |
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|
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/** Create a token buffer */ |
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TokenBuffer::TokenBuffer( TokenStream& inp ) |
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: input(inp) |
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, nMarkers(0) |
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, markerOffset(0) |
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, numToConsume(0) |
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{ |
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} |
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|
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TokenBuffer::~TokenBuffer( void ) |
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{ |
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} |
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|
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/** Ensure that the token buffer is sufficiently full */ |
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void TokenBuffer::fill(unsigned int amount) |
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{ |
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syncConsume(); |
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// Fill the buffer sufficiently to hold needed tokens |
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while (queue.entries() < (amount + markerOffset)) |
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{ |
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// Append the next token |
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queue.append(input.nextToken()); |
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} |
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} |
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|
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/** Get a lookahead token value */ |
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int TokenBuffer::LA(unsigned int i) |
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{ |
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fill(i); |
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return queue.elementAt(markerOffset+i-1)->getType(); |
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} |
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|
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/** Get a lookahead token */ |
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RefToken TokenBuffer::LT(unsigned int i) |
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{ |
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fill(i); |
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return queue.elementAt(markerOffset+i-1); |
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} |
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|
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/** Return an integer marker that can be used to rewind the buffer to |
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* its current state. |
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*/ |
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unsigned int TokenBuffer::mark() |
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{ |
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syncConsume(); |
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nMarkers++; |
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return markerOffset; |
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} |
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|
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/**Rewind the token buffer to a marker. |
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* @param mark Marker returned previously from mark() |
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*/ |
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void TokenBuffer::rewind(unsigned int mark) |
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{ |
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syncConsume(); |
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markerOffset=mark; |
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nMarkers--; |
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} |
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|
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/// Get number of non-consumed tokens |
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unsigned int TokenBuffer::entries() const |
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{ |
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return queue.entries() - markerOffset; |
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} |
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|
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#ifdef ANTLR_CXX_SUPPORTS_NAMESPACE |
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} |
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#endif |
