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/*
* Copyright (c) 2015-2018, 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 Stop Alphabet calculation.
*/
#include "ng_stop.h"
#include "ng_depth.h"
#include "ng_holder.h"
#include "ng_misc_opt.h"
#include "ng_util.h"
#include "ue2common.h"
#include "nfa/castlecompile.h"
#include "som/som.h"
#include "util/charreach.h"
#include "util/container.h"
#include "util/dump_charclass.h"
#include "util/graph.h"
#include "util/graph_range.h"
#include "util/verify_types.h"
#include <map>
#include <set>
#include <vector>
using namespace std;
namespace ue2 {
/** Stop alphabet depth threshold. */
static const u32 MAX_STOP_DEPTH = 8;
namespace {
/** Depths from start, startDs for this graph. */
struct InitDepths {
explicit InitDepths(const NGHolder &g)
: start(calcDepthsFrom(g, g.start)),
startDs(calcDepthsFrom(g, g.startDs)) {}
depth maxDist(const NGHolder &g, NFAVertex v) const {
u32 idx = g[v].index;
assert(idx < start.size() && idx < startDs.size());
const depth &d_start = start.at(idx).max;
const depth &d_startDs = startDs.at(idx).max;
if (d_start.is_unreachable()) {
return d_startDs;
} else if (d_startDs.is_unreachable()) {
return d_start;
}
return max(d_start, d_startDs);
}
private:
vector<DepthMinMax> start;
vector<DepthMinMax> startDs;
};
} // namespace
/** Find the set of characters that are not present in the reachability of
* graph \p g after a certain depth (currently 8). If a character in this set
* is encountered, it means that the NFA is either dead or has not progressed
* more than 8 characters from its start states.
*
* This is only used to guide merging heuristics, use
* findLeftOffsetStopAlphabet for real uses.
*/
CharReach findStopAlphabet(const NGHolder &g, som_type som) {
const depth max_depth(MAX_STOP_DEPTH);
const InitDepths depths(g);
const map<NFAVertex, BoundedRepeatSummary> no_vertices;
CharReach stopcr;
for (auto v : vertices_range(g)) {
if (is_special(v, g)) {
continue;
}
if (depths.maxDist(g, v) >= max_depth) {
if (som == SOM_NONE) {
stopcr |= reduced_cr(v, g, no_vertices);
} else {
stopcr |= g[v].char_reach;
}
}
}
// Turn alphabet into stops.
stopcr.flip();
return stopcr;
}
/** Calculate the stop alphabet for each depth from 0 to MAX_STOP_DEPTH. Then
* build an eight-bit mask per character C, with each bit representing the
* depth before the location of character C (if encountered) that the NFA would
* be in a predictable start state. */
vector<u8> findLeftOffsetStopAlphabet(const NGHolder &g, som_type som) {
const depth max_depth(MAX_STOP_DEPTH);
const InitDepths depths(g);
const map<NFAVertex, BoundedRepeatSummary> no_vertices;
vector<CharReach> reach(MAX_STOP_DEPTH);
for (auto v : vertices_range(g)) {
if (is_special(v, g)) {
continue;
}
CharReach v_cr;
if (som == SOM_NONE) {
v_cr = reduced_cr(v, g, no_vertices);
} else {
v_cr = g[v].char_reach;
}
u32 d = min(max_depth, depths.maxDist(g, v));
for (u32 i = 0; i < d; i++) {
reach[i] |= v_cr;
}
}
#ifdef DEBUG
for (u32 i = 0; i < MAX_STOP_DEPTH; i++) {
DEBUG_PRINTF("depth %u, stop chars: ", i);
describeClass(stdout, ~reach[i], 20, CC_OUT_TEXT);
printf("\n");
}
#endif
vector<u8> stop(N_CHARS, 0);
for (u32 i = 0; i < MAX_STOP_DEPTH; i++) {
CharReach cr = ~reach[i]; // invert reach for stop chars.
const u8 mask = 1U << i;
for (size_t c = cr.find_first(); c != cr.npos; c = cr.find_next(c)) {
stop[c] |= mask;
}
}
return stop;
}
vector<u8> findLeftOffsetStopAlphabet(const CastleProto &castle,
UNUSED som_type som) {
const depth max_width = findMaxWidth(castle);
DEBUG_PRINTF("castle has reach %s and max width %s\n",
describeClass(castle.reach()).c_str(),
max_width.str().c_str());
const CharReach escape = ~castle.reach(); // invert reach for stop chars.
u32 d = min(max_width, depth(MAX_STOP_DEPTH));
const u8 mask = verify_u8((1U << d) - 1);
vector<u8> stop(N_CHARS, 0);
for (size_t c = escape.find_first(); c != escape.npos;
c = escape.find_next(c)) {
stop[c] |= mask;
}
return stop;
}
} // namespace ue2
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