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#ifndef QPARSER_H

#define QPARSER_H

#include <QtCore/QSharedDataPointer>

#include <QtCore/QVarLengthArray>

template <typename _Parser, typename _Table, typename _Value = int>

class QParser: protected _Table

{

public:

    QParser();

    ~QParser();

    bool parse();

    inline _Value &sym(int index);

private:

    inline int nextToken()

    {

        return static_cast<_Parser*> (this)->nextToken();

    }

    inline void consumeRule(int rule)

    {

        static_cast<_Parser*> (this)->consumeRule(rule);

    }

    enum { DefaultStackSize = 128 };

    struct Data: public QSharedData

    {

        Data(): stackSize (DefaultStackSize), tos (0) {}

        QVarLengthArray<int, DefaultStackSize> stateStack;

        QVarLengthArray<_Value, DefaultStackSize> parseStack;

        int stackSize;

        int tos;

        void reallocateStack() {

            stackSize <<= 1;

            stateStack.resize(stackSize);

            parseStack.resize(stackSize);

        }

    };

    QSharedDataPointer<Data> d;

};

template <typename _Parser, typename _Table, typename _Value>

inline _Value &QParser<_Parser, _Table, _Value>::sym(int n)

{

    return d->parseStack [d->tos + n - 1];

}

template <typename _Parser, typename _Table, typename _Value>

QParser<_Parser, _Table, _Value>::QParser():

    d(new Data())

{

}

template <typename _Parser, typename _Table, typename _Value>

QParser<_Parser, _Table, _Value>::~QParser()

{

}

template <typename _Parser, typename _Table, typename _Value>

bool QParser<_Parser, _Table, _Value>::parse()

{

    const int INITIAL_STATE = 0;

    d->tos = 0;

    d->reallocateStack();

    int act = d->stateStack[++d->tos] = INITIAL_STATE;

    int token = -1;

    forever {

        if (token == -1 && - _Table::TERMINAL_COUNT != _Table::action_index[act])

            token = nextToken();

        act = _Table::t_action(act, token);

        if (d->stateStack[d->tos] == _Table::ACCEPT_STATE)

            return true;

        else if (act > 0) {

            if (++d->tos == d->stackSize)

                d->reallocateStack();

            d->parseStack[d->tos] = d->parseStack[d->tos - 1];

            d->stateStack[d->tos] = act;

            token = -1;

        }

        else if (act < 0) {

            int r = - act - 1;

            d->tos -= _Table::rhs[r];

            act = d->stateStack[d->tos++];

            consumeRule(r);

            act = d->stateStack[d->tos] = _Table::nt_action(act, _Table::lhs[r] - _Table::TERMINAL_COUNT);

        }

        else break;

    }

    return false;

}

#endif // QPARSER_H