vectorscan/src/parser/ComponentRepeat.h

/*
 * Copyright (c) 2015, Intel Corporation
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 *    notice, this list of conditions and the following disclaimer in the
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 *    may be used to endorse or promote products derived from this software
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 *
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/** \file
 * \brief Repeats ('*', '+', '?', '{M,N}', etc)
 */

#ifndef RE_COMPONENTREPEAT_H
#define RE_COMPONENTREPEAT_H

#include "Component.h"
#include "position.h"
#include "ue2common.h"

#include <memory>
#include <utility>

namespace ue2 {

/**
 * \brief Encapsulates a repeat of a subexpression ('*', '+', '?', '{M,N}',
 * etc).
 *
 * ASCII Art Time:
 *
 * Our standard representation of standard repeats. Other constructions (fan-in
 * vs fan-out) would also be possible and equivalent for our purposes.
 *
 * {n,m}
 *
 *     S->M->M->M->O->O->O->T
 *              |     ^  ^  ^
 *              |     |  |  |
 *              \-----------/
 *
 * {0,m}
 *
 *     /-----------\
 *     |           |
 *     |           V
 *     S->O->O->O->T
 *        |  ^  ^  ^
 *        |  |  |  |
 *        \--------/
 *
 */
class ComponentRepeat : public Component {
    friend class ConstructLiteralVisitor;
    friend class DumpVisitor;
    friend class PrintVisitor;
    friend class SimplifyVisitor;
public:
    /** \brief Value representing no maximum bound. */
    static constexpr u32 NoLimit = 0xffffffff;

    /** \brief Type of this repeat, characterising its
     * greediness/possessiveness. */
    enum RepeatType {
        /** Minimising repeat, like 'a*?'. */
        REPEAT_NONGREEDY,
        /** Maximising repeat, like 'a*'. This is the default in PCRE. */
        REPEAT_GREEDY,
        /** Possessive, maximising repeat, like 'a*+'. Possessive repeats are
         * only currently supported in prefiltering mode, where we treat them
         * the same way we treat normal greedy repeats. */
        REPEAT_POSSESSIVE,
    };

    ComponentRepeat(std::unique_ptr<Component> sub_comp, u32 min, u32 max,
                    RepeatType t);
    ~ComponentRepeat() override;
    ComponentRepeat *clone() const override;
    Component *accept(ComponentVisitor &v) override;
    void accept(ConstComponentVisitor &v) const override;

    std::vector<PositionInfo> first() const override;
    std::vector<PositionInfo> last() const override;
    bool empty() const override;
    bool repeatable() const override;
    bool vacuous_everywhere() const override;
    void notePositions(GlushkovBuildState &bs) override;
    void buildFollowSet(GlushkovBuildState &bs,
                        const std::vector<PositionInfo> &lastPos) override;
    bool checkEmbeddedStartAnchor(bool at_start) const override;
    bool checkEmbeddedEndAnchor(bool at_end) const override;

    void optimise(bool connected_to_sds) override;

    virtual std::pair<u32, u32> getBounds() const {
        return std::make_pair(m_min, m_max);
    }

    /** \brief From declared behaviour (not taking into account the
     * sub-component).  */
    enum RepeatType type;

protected:
    void postSubNotePositionHook();
    void wireRepeats(GlushkovBuildState &bs);

    std::unique_ptr<Component> sub_comp;
    u32 m_min;
    u32 m_max;

    std::vector<std::vector<PositionInfo> > m_firsts;
    std::vector<std::vector<PositionInfo> > m_lasts;
    Position posFirst;
    Position posLast;

    ComponentRepeat(const ComponentRepeat &other);
};

std::unique_ptr<ComponentRepeat>
makeComponentRepeat(std::unique_ptr<Component> sub_comp, u32 min, u32 max,
                    ComponentRepeat::RepeatType t);

} // namespace ue2

#endif // _RE_COMPONENTREPEAT_H_