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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 Literal Component Splitting. Identifies literals that span the
* graph and moves them into Rose.
*/
#include "ng_literal_component.h"
#include "grey.h"
#include "ng.h"
#include "ng_prune.h"
#include "ng_util.h"
#include "ue2common.h"
#include "compiler/compiler.h"
#include "rose/rose_build.h"
#include "util/container.h"
#include "util/graph.h"
#include "util/graph_range.h"
#include "util/ue2string.h"
#include <unordered_set>
using namespace std;
namespace ue2 {
static
bool isLiteralChar(const NGHolder &g, NFAVertex v, bool &nocase,
bool &casefixed) {
const CharReach &cr = g[v].char_reach;
const size_t num = cr.count();
if (num > 2) {
return false; // char class
}
if (!casefixed) {
if (num == 2 && cr.isCaselessChar()) {
nocase = true;
casefixed = true;
return true;
} else if (num == 1) {
if (cr.isAlpha()) {
nocase = false;
casefixed = true;
}
// otherwise, still acceptable but we can't fix caselessness yet
return true;
}
} else {
// nocase property is fixed
if (nocase) {
if ((num == 2 && cr.isCaselessChar()) ||
(num == 1 && !cr.isAlpha())) {
return true;
}
} else {
return (num == 1);
}
}
return false;
}
static
void addToString(string &s, const NGHolder &g, NFAVertex v) {
const CharReach &cr = g[v].char_reach;
assert(cr.count() == 1 || cr.isCaselessChar());
char c = (char)cr.find_first();
s.push_back(c);
}
static
bool splitOffLiteral(NG &ng, NGHolder &g, NFAVertex v, const bool anchored,
set<NFAVertex> &dead) {
DEBUG_PRINTF("examine vertex %zu\n", g[v].index);
bool nocase = false, casefixed = false;
assert(!is_special(v, g));
size_t reqInDegree;
if (anchored) {
reqInDegree = 1;
assert(edge(g.start, v, g).second);
} else {
reqInDegree = 2;
assert(edge(g.start, v, g).second);
assert(edge(g.startDs, v, g).second);
}
if (in_degree(v, g) > reqInDegree) {
DEBUG_PRINTF("extra in-edges\n");
return false;
}
if (!isLiteralChar(g, v, nocase, casefixed)) {
DEBUG_PRINTF("not literal\n");
return false;
}
string literal;
addToString(literal, g, v);
// Remaining vertices must come in a chain, each with one in-edge and one
// out-edge only.
NFAVertex u;
while (1) {
if (out_degree(v, g) != 1) {
DEBUG_PRINTF("branches, not literal\n");
return false;
}
u = v; // previous vertex
v = *(adjacent_vertices(v, g).first);
DEBUG_PRINTF("loop, v=%zu\n", g[v].index);
if (is_special(v, g)) {
if (v == g.accept || v == g.acceptEod) {
break; // OK
} else {
assert(0); // start?
return false;
}
} else {
// Ordinary, must be literal
if (!isLiteralChar(g, v, nocase, casefixed)) {
DEBUG_PRINTF("not literal\n");
return false;
}
if (in_degree(v, g) != 1) {
DEBUG_PRINTF("branches, not literal\n");
return false;
}
}
addToString(literal, g, v);
}
// Successfully found a literal; there might be multiple report IDs, in
// which case we add all the reports.
assert(!is_special(u, g));
bool eod = v == g.acceptEod;
assert(eod || v == g.accept);
DEBUG_PRINTF("success: found %s literal '%s'\n",
anchored ? "anchored" : "unanchored",
escapeString(literal).c_str());
// Literals of length 1 are better served going through later optimisation
// passes, where they might be combined together into a character class.
if (literal.length() == 1) {
DEBUG_PRINTF("skipping literal of length 1\n");
return false;
}
ng.rose->add(anchored, eod, ue2_literal(literal, nocase), g[u].reports);
// Remove the terminal vertex. Later, we rely on pruneUseless to remove the
// other vertices in this chain, since they'll no longer lead to an accept.
dead.insert(u);
return true;
}
/** \brief Split off literals. True if any changes were made to the graph. */
bool splitOffLiterals(NG &ng, NGHolder &g) {
if (!ng.cc.grey.allowLiteral) {
return false;
}
bool changed = false;
set<NFAVertex> dead;
unordered_set<NFAVertex> unanchored; // for faster lookup.
insert(&unanchored, adjacent_vertices(g.startDs, g));
// Anchored literals.
for (auto v : adjacent_vertices_range(g.start, g)) {
if (!is_special(v, g) && !contains(unanchored, v)) {
changed |= splitOffLiteral(ng, g, v, true, dead);
}
}
// Unanchored literals.
for (auto v : adjacent_vertices_range(g.startDs, g)) {
if (!is_special(v, g)) {
changed |= splitOffLiteral(ng, g, v, false, dead);
}
}
if (changed) {
remove_vertices(dead, g);
pruneUseless(g);
return true;
}
return false;
}
} // namespace ue2
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