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tim |
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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: TokenStreamHiddenTokenFilter.cpp,v 1.1 2005-12-02 15:38:02 tim Exp $ |
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*/ |
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#include "antlr/TokenStreamHiddenTokenFilter.hpp" |
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#include "antlr/CommonHiddenStreamToken.hpp" |
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#ifdef ANTLR_CXX_SUPPORTS_NAMESPACE |
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namespace antlr { |
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#endif |
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/**This object filters a token stream coming from a lexer |
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* or another TokenStream so that only certain token channels |
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* get transmitted to the parser. |
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* |
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* Any of the channels can be filtered off as "hidden" channels whose |
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* tokens can be accessed from the parser. |
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*/ |
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TokenStreamHiddenTokenFilter::TokenStreamHiddenTokenFilter(TokenStream& input) |
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: TokenStreamBasicFilter(input) |
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{ |
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} |
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void TokenStreamHiddenTokenFilter::consume() |
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{ |
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nextMonitoredToken = input->nextToken(); |
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} |
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void TokenStreamHiddenTokenFilter::consumeFirst() |
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{ |
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consume(); |
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// Handle situation where hidden or discarded tokens |
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// appear first in input stream |
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RefToken p; |
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// while hidden or discarded scarf tokens |
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while ( hideMask.member(LA(1)->getType()) || discardMask.member(LA(1)->getType()) ) { |
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if ( hideMask.member(LA(1)->getType()) ) { |
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if ( !p ) { |
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p = LA(1); |
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} |
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else { |
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static_cast<CommonHiddenStreamToken*>(p.get())->setHiddenAfter(LA(1)); |
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static_cast<CommonHiddenStreamToken*>(LA(1).get())->setHiddenBefore(p); // double-link |
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p = LA(1); |
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} |
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lastHiddenToken = p; |
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if (!firstHidden) |
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firstHidden = p; // record hidden token if first |
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} |
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consume(); |
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} |
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} |
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BitSet TokenStreamHiddenTokenFilter::getDiscardMask() const |
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{ |
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return discardMask; |
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} |
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/** Return a ptr to the hidden token appearing immediately after |
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* token t in the input stream. |
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*/ |
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RefToken TokenStreamHiddenTokenFilter::getHiddenAfter(RefToken t) |
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{ |
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return static_cast<CommonHiddenStreamToken*>(t.get())->getHiddenAfter(); |
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} |
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/** Return a ptr to the hidden token appearing immediately before |
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* token t in the input stream. |
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*/ |
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RefToken TokenStreamHiddenTokenFilter::getHiddenBefore(RefToken t) |
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{ |
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return static_cast<CommonHiddenStreamToken*>(t.get())->getHiddenBefore(); |
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} |
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BitSet TokenStreamHiddenTokenFilter::getHideMask() const |
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{ |
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return hideMask; |
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} |
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/** Return the first hidden token if one appears |
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* before any monitored token. |
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*/ |
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RefToken TokenStreamHiddenTokenFilter::getInitialHiddenToken() |
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{ |
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return firstHidden; |
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} |
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void TokenStreamHiddenTokenFilter::hide(int m) |
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{ |
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hideMask.add(m); |
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} |
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void TokenStreamHiddenTokenFilter::hide(const BitSet& mask) |
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{ |
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hideMask = mask; |
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} |
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RefToken TokenStreamHiddenTokenFilter::LA(int) |
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{ |
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return nextMonitoredToken; |
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} |
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/** Return the next monitored token. |
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* Test the token following the monitored token. |
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* If following is another monitored token, save it |
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* for the next invocation of nextToken (like a single |
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* lookahead token) and return it then. |
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* If following is unmonitored, nondiscarded (hidden) |
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* channel token, add it to the monitored token. |
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* |
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* Note: EOF must be a monitored Token. |
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*/ |
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RefToken TokenStreamHiddenTokenFilter::nextToken() |
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{ |
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// handle an initial condition; don't want to get lookahead |
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// token of this splitter until first call to nextToken |
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if ( !LA(1) ) { |
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consumeFirst(); |
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} |
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// we always consume hidden tokens after monitored, thus, |
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// upon entry LA(1) is a monitored token. |
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RefToken monitored = LA(1); |
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// point to hidden tokens found during last invocation |
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static_cast<CommonHiddenStreamToken*>(monitored.get())->setHiddenBefore(lastHiddenToken); |
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lastHiddenToken = nullToken; |
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// Look for hidden tokens, hook them into list emanating |
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// from the monitored tokens. |
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consume(); |
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RefToken p = monitored; |
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// while hidden or discarded scarf tokens |
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while ( hideMask.member(LA(1)->getType()) || discardMask.member(LA(1)->getType()) ) { |
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if ( hideMask.member(LA(1)->getType()) ) { |
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// attach the hidden token to the monitored in a chain |
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// link forwards |
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static_cast<CommonHiddenStreamToken*>(p.get())->setHiddenAfter(LA(1)); |
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// link backwards |
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if (p != monitored) { //hidden cannot point to monitored tokens |
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static_cast<CommonHiddenStreamToken*>(LA(1).get())->setHiddenBefore(p); |
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} |
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p = lastHiddenToken = LA(1); |
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} |
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consume(); |
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} |
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return monitored; |
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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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