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#ifndef INC_InputBuffer_hpp__ |
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#define INC_InputBuffer_hpp__ |
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|
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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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* $Id$ |
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*/ |
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|
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#include <antlr/config.hpp> |
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#include <antlr/CircularQueue.hpp> |
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#include <string> |
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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 characters fed to the lexer from a InputStream 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 characters. Normally, |
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* "k" characters are stored in the buffer. More characters 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 characters is deferred. In other words, reading the next |
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* character 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.CharQueue |
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*/ |
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class ANTLR_API InputBuffer { |
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public: |
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/** Create a character buffer */ |
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InputBuffer() |
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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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virtual ~InputBuffer() |
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{ |
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} |
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|
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/// Reset the input buffer to empty state |
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virtual inline void reset( void ) |
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{ |
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nMarkers = 0; |
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markerOffset = 0; |
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numToConsume = 0; |
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queue.clear(); |
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} |
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|
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/** This method updates the state of the input buffer so that |
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* the text matched since the most recent mark() is no longer |
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* held by the buffer. So, you either do a mark/rewind for |
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* failed predicate or mark/commit to keep on parsing without |
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* rewinding the input. |
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*/ |
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inline void commit( void ) |
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{ |
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nMarkers--; |
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} |
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|
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/** Mark another character for deferred consumption */ |
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virtual inline void consume() |
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{ |
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numToConsume++; |
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} |
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|
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/** Ensure that the character buffer is sufficiently full */ |
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virtual void fill(unsigned int amount); |
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|
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/** Override this in subclasses to get the next character */ |
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virtual int getChar()=0; |
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|
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/** Get a lookahead character */ |
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virtual inline int LA(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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virtual unsigned int mark(); |
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/// Are there any marks active in the InputBuffer |
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virtual inline bool isMarked() const |
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{ |
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return (nMarkers != 0); |
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} |
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/** Rewind the character buffer to a marker. |
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* @param mark Marker returned previously from mark() |
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*/ |
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virtual void rewind(unsigned int mark); |
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|
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/** Get the number of non-consumed characters |
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*/ |
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virtual unsigned int entries() const; |
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|
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ANTLR_USE_NAMESPACE(std)string getLAChars() const; |
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|
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ANTLR_USE_NAMESPACE(std)string getMarkedChars() const; |
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|
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protected: |
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// char source |
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// leave to subclasses |
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|
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// Number of active markers |
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unsigned int nMarkers; // = 0; |
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|
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// Additional offset used when markers are active |
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unsigned int markerOffset; // = 0; |
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|
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// Number of calls to consume() since last LA() or LT() call |
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unsigned int numToConsume; // = 0; |
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|
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// Circular queue |
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CircularQueue<int> queue; |
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|
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/** Sync up deferred consumption */ |
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void syncConsume(); |
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|
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private: |
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InputBuffer(const InputBuffer& other); |
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InputBuffer& operator=(const InputBuffer& other); |
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}; |
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|
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/** Sync up deferred consumption */ |
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inline void InputBuffer::syncConsume() { |
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if (numToConsume > 0) |
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{ |
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if (nMarkers > 0) |
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markerOffset += numToConsume; |
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else |
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queue.removeItems( numToConsume ); |
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numToConsume = 0; |
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} |
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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 |
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|
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#endif //INC_InputBuffer_hpp__ |
