antlr/include/antlr/CircularQueue.hpp

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#ifndef INC_CircularQueue_hpp__
#define INC_CircularQueue_hpp__

/* ANTLR Translator Generator
 * Project led by Terence Parr at http://www.jGuru.com
 * Software rights: http://www.antlr.org/license.html
 *
 * $Id: //depot/code/org.antlr/release/antlr-2.7.7/lib/cpp/antlr/CircularQueue.hpp#2 $
 */

#include <antlr/config.hpp>
#include <antlr/Token.hpp>
#include <vector>
#include <cassert>

#ifdef ANTLR_CXX_SUPPORTS_NAMESPACE
namespace antlr {
#endif

// Resize every 5000 items
#define OFFSET_MAX_RESIZE 5000

template <class T>
class ANTLR_API CircularQueue {
public:
        CircularQueue()
        : storage()
        , m_offset(0)
        {
        }
        ~CircularQueue()
        {
        }

        inline void clear( void )
        {
                m_offset = 0;
                storage.clear();
        }

        inline T elementAt( size_t idx ) const
        {
                return storage[idx+m_offset];
        }
        void removeFirst()
        {
                if (m_offset >= OFFSET_MAX_RESIZE)
                {
                        storage.erase( storage.begin(), storage.begin() + m_offset + 1 );
                        m_offset = 0;
                }
                else
                        ++m_offset;
        }
        inline void removeItems( size_t nb )
        {
                // it would be nice if we would not get called with nb > entries
                // (or to be precise when entries() == 0)
                // This case is possible when lexer/parser::recover() calls
                // consume+consumeUntil when the queue is empty.
                // In recover the consume says to prepare to read another
                // character/token. Then in the subsequent consumeUntil the
                // LA() call will trigger
                // syncConsume which calls this method *before* the same queue
                // has been sufficiently filled.
                if( nb > entries() )
                        nb = entries();

                if (m_offset >= OFFSET_MAX_RESIZE)
                {
                        storage.erase( storage.begin(), storage.begin() + m_offset + nb );
                        m_offset = 0;
                }
                else
                        m_offset += nb;
        }
        inline void append(const T& t)
        {
                storage.push_back(t);
        }
        inline size_t entries() const
        {
                return storage.size() - m_offset;
        }

private:
        ANTLR_USE_NAMESPACE(std)vector<T> storage;
        size_t m_offset;

        CircularQueue(const CircularQueue&);
        const CircularQueue& operator=(const CircularQueue&);
};

#ifdef ANTLR_CXX_SUPPORTS_NAMESPACE
}
#endif

#endif //INC_CircularQueue_hpp__

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