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/*
* 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:
*
* * Redistributions of source code must retain the above copyright notice,
* 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
* documentation and/or other materials provided with the distribution.
* * Neither the name of Intel Corporation nor the names of its contributors
* 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
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
/** \file
* \brief DFA determinisation code.
*/
#ifndef DETERMINISE_H
#define DETERMINISE_H
#include "nfagraph/ng_holder.h"
#include "charreach.h"
#include "container.h"
#include "ue2common.h"
#include <algorithm>
#include <array>
#include <queue>
#include <vector>
namespace ue2 {
/* Automaton details:
*
* const vector<StateSet> initial()
* returns initial states to start determinising from. StateSets in the
* initial() vector will given consecutive ids starting from 1, in the order
* that they appear.
*
* void reports(StateSet s, flat_set<ReportID> *out)
* fills out with any reports that need to be raised for stateset.
*
* void reportsEod(StateSet s, flat_set<ReportID> *out)
* fills out with any reports that need to be raised for stateset at EOD.
*
* void transition(const StateSet &in, StateSet *next)
* fills the next array such next[i] is the stateset that in transitions to
* on seeing symbol i (i is in the compressed alphabet of the automaton).
*
* u16 alphasize
* size of the compressed alphabet
*/
/** \brief determinises some sort of nfa
* \param n the automaton to determinise
* \param dstates_out output dfa states
* \param state_limit limit on the number of dfa states to construct
* \param statesets_out a mapping from DFA state to the set of NFA states in
* the automaton
* \return true on success, false if state limit exceeded
*/
template<class Auto, class ds>
never_inline
bool determinise(Auto &n, std::vector<ds> &dstates, size_t state_limit,
std::vector<typename Auto::StateSet> *statesets_out = nullptr) {
DEBUG_PRINTF("the determinator\n");
using StateSet = typename Auto::StateSet;
typename Auto::StateMap dstate_ids;
const size_t alphabet_size = n.alphasize;
dstates.clear();
dstates.reserve(state_limit);
dstate_ids.emplace(n.dead, DEAD_STATE);
dstates.push_back(ds(alphabet_size));
std::fill_n(dstates[0].next.begin(), alphabet_size, DEAD_STATE);
std::queue<std::pair<StateSet, dstate_id_t>> q;
q.emplace(n.dead, DEAD_STATE);
const std::vector<StateSet> &init = n.initial();
for (u32 i = 0; i < init.size(); i++) {
q.emplace(init[i], dstates.size());
assert(!contains(dstate_ids, init[i]));
dstate_ids.emplace(init[i], dstates.size());
dstates.push_back(ds(alphabet_size));
}
std::vector<StateSet> succs(alphabet_size, n.dead);
while (!q.empty()) {
auto m = std::move(q.front());
q.pop();
StateSet &curr = m.first;
dstate_id_t curr_id = m.second;
DEBUG_PRINTF("curr: %hu\n", curr_id);
/* fill in accepts */
n.reports(curr, dstates[curr_id].reports);
n.reportsEod(curr, dstates[curr_id].reports_eod);
if (!dstates[curr_id].reports.empty()) {
DEBUG_PRINTF("curr: %hu: is accept\n", curr_id);
}
if (!dstates[curr_id].reports.empty()) {
/* only external reports set ekeys */
if (n.canPrune(dstates[curr_id].reports)) {
/* we only transition to dead on characters, TOPs leave us
* alone */
std::fill_n(dstates[curr_id].next.begin(), alphabet_size,
DEAD_STATE);
dstates[curr_id].next[n.alpha[TOP]] = curr_id;
continue;
}
}
/* fill in successor states */
n.transition(curr, &succs[0]);
for (symbol_t s = 0; s < n.alphasize; s++) {
dstate_id_t succ_id;
if (s && succs[s] == succs[s - 1]) {
succ_id = dstates[curr_id].next[s - 1];
} else {
auto p = dstate_ids.find(succs[s]);
if (p != dstate_ids.end()) { // succ[s] is already present
succ_id = p->second;
if (succ_id > curr_id && !dstates[succ_id].daddy
&& n.unalpha[s] < N_CHARS) {
dstates[succ_id].daddy = curr_id;
}
} else {
succ_id = dstate_ids.size();
dstate_ids.emplace(succs[s], succ_id);
dstates.push_back(ds(alphabet_size));
dstates.back().daddy = n.unalpha[s] < N_CHARS ? curr_id : 0;
q.emplace(succs[s], succ_id);
}
DEBUG_PRINTF("-->%hu on %02hx\n", succ_id, n.unalpha[s]);
}
if (succ_id >= state_limit) {
DEBUG_PRINTF("succ_id %hu >= state_limit %zu\n",
succ_id, state_limit);
dstates.clear();
return false;
}
dstates[curr_id].next[s] = succ_id;
}
}
// The dstates vector will persist in the raw_dfa.
dstates.shrink_to_fit();
if (statesets_out) {
auto &statesets = *statesets_out;
statesets.resize(dstate_ids.size());
for (auto &m : dstate_ids) {
statesets[m.second] = std::move(m.first);
}
}
DEBUG_PRINTF("ok\n");
return true;
}
static inline
std::vector<CharReach> populateCR(const NGHolder &g,
const std::vector<NFAVertex> &v_by_index,
const std::array<u16, ALPHABET_SIZE> &alpha) {
std::vector<CharReach> cr_by_index(v_by_index.size());
for (size_t i = 0; i < v_by_index.size(); i++) {
const CharReach &cr = g[v_by_index[i]].char_reach;
CharReach &cr_out = cr_by_index[i];
for (size_t s = cr.find_first(); s != cr.npos; s = cr.find_next(s)) {
cr_out.set(alpha[s]);
}
}
return cr_by_index;
}
} // namespace ue2
#endif
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