vectorscan/src/nfa/castlecompile.h

/*
 * Copyright (c) 2015-2017, Intel Corporation
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
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 *    this list of conditions and the following disclaimer.
 *  * Redistributions in binary form must reproduce the above copyright
 *    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
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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/**
 * \file
 * \brief Castle: multi-tenant repeat engine, compiler code.
 */

#ifndef NFA_CASTLECOMPILE_H
#define NFA_CASTLECOMPILE_H

#include "nfa_kind.h"
#include "ue2common.h"
#include "nfagraph/ng_repeat.h"
#include "util/bytecode_ptr.h"
#include "util/depth.h"
#include "util/flat_containers.h"

#include <map>
#include <memory>
#include <set>
#include <unordered_map>
#include <vector>

struct NFA;

namespace ue2 {

class CharReach;
class NGHolder;
class ReportManager;
struct CompileContext;

/**
 * \brief Prototype for a Castle engine: contains at least one CastleRepeat.
 *
 * Currently, all repeats in a Castle must have the same character
 * reachability.
 *
 * A CastleProto is converted into a single NFA, with each top triggering a
 * unique repeat. A CastleProto can contain at most CastleProto::max_occupancy
 * elements.
 */
struct CastleProto {
    static constexpr size_t max_occupancy = 65536; // arbitrary limit
    CastleProto(nfa_kind k, const PureRepeat &pr);
    const CharReach &reach() const;

    /** \brief Add a new repeat. */
    u32 add(const PureRepeat &pr);

    /** \brief Remove a repeat. */
    void erase(u32 top);

    /**
     * \brief Merge in the given repeat, returning the top used.
     *
     * If the repeat already exists in this castle, we will re-use (and return)
     * the old top. If it doesn't, it will be added and assigned a new top.
     * Returns \ref max_occupancy if capacity would be exceeded.
     */
    u32 merge(const PureRepeat &pr);

    /** \brief Mapping from unique top id to repeat. */
    std::map<u32, PureRepeat> repeats;

    /** \brief Mapping from report to associated tops. */
    std::unordered_map<ReportID, flat_set<u32>> report_map;

    /**
     * \brief Next top id to use. Repeats may be removed without top remapping,
     * so we track this explicitly instead of using repeats.size().
     */
    u32 next_top = 1;

    /** \brief Kind for this engine. */
    nfa_kind kind;
};

std::set<ReportID> all_reports(const CastleProto &proto);
depth findMinWidth(const CastleProto &proto);
depth findMaxWidth(const CastleProto &proto);
depth findMinWidth(const CastleProto &proto, u32 top);
depth findMaxWidth(const CastleProto &proto, u32 top);

/**
 * \brief Remap tops to be contiguous.
 *
 * Remap the tops in the given CastleProto so that they're contiguous in the
 * range [0 .. N-1].
 */
void remapCastleTops(CastleProto &proto, std::map<u32, u32> &top_map);

/**
 * \brief Construct an NFA from a CastleProto.
 *
 * NOTE: Tops must be contiguous, i.e. \ref remapCastleTops must have been run
 * first.
 */
bytecode_ptr<NFA>
buildCastle(const CastleProto &proto,
            const std::map<u32, std::vector<std::vector<CharReach>>> &triggers,
            const CompileContext &cc, const ReportManager &rm);

/**
 * \brief Merge two CastleProto prototypes together, if possible. If a
 * particular repeat from c2 is already in c1, then it will be reused rather
 * than adding a duplicate repeat.
 *
 * Returns true if merge of all repeats in c2 into c1 succeeds, and fills
 * mapping with the repeat indices.
 */
bool mergeCastle(CastleProto &c1, const CastleProto &c2,
                 std::map<u32, u32> &top_map);

/**
 * \brief True if the two castles are identical with respect to the reports
 * given; i.e. the same tops lead to the same repeats, just with report1 in c1
 * and report2 in c2.
 *
 * Repeats leading to other reports are ignored.
 */
bool is_equal(const CastleProto &c1, ReportID report1, const CastleProto &c2,
              ReportID report2);

/**
 * \brief True if the two castles given are identical.
 */
bool is_equal(const CastleProto &c1, const CastleProto &c2);

/**
 * \brief True if the given castle contains more than a single instance of any
 * of the reports in the given set.
 */
bool requiresDedupe(const CastleProto &proto,
                    const flat_set<ReportID> &reports);

/**
 * \brief Build an NGHolder from a CastleProto.
 */
std::unique_ptr<NGHolder> makeHolder(const CastleProto &castle,
                                     const CompileContext &cc);

} // namespace ue2

#endif // NFA_CASTLECOMPILE_H