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// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only WITH Qt-GPL-exception-1.0
#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
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