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97 lines
2.1 KiB
97 lines
2.1 KiB
/* 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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* $Id$
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*/
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#include "antlr/TokenBuffer.h"
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#ifdef ANTLR_CXX_SUPPORTS_NAMESPACE
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namespace antlr {
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#endif
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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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/** 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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TokenBuffer::~TokenBuffer( void )
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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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/** 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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/** 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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/** 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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/**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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/// 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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#ifdef ANTLR_CXX_SUPPORTS_NAMESPACE
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}
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#endif
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