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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "extensions/common/matcher/substring_set_matcher.h"
#include <queue>
#include "base/logging.h"
#include "base/stl_util.h"
namespace extensions {
//
// SubstringSetMatcher
//
SubstringSetMatcher::SubstringSetMatcher() {
RebuildAhoCorasickTree();
}
SubstringSetMatcher::~SubstringSetMatcher() {}
void SubstringSetMatcher::RegisterPatterns(
const std::vector<const StringPattern*>& patterns) {
RegisterAndUnregisterPatterns(patterns,
std::vector<const StringPattern*>());
}
void SubstringSetMatcher::UnregisterPatterns(
const std::vector<const StringPattern*>& patterns) {
RegisterAndUnregisterPatterns(std::vector<const StringPattern*>(),
patterns);
}
void SubstringSetMatcher::RegisterAndUnregisterPatterns(
const std::vector<const StringPattern*>& to_register,
const std::vector<const StringPattern*>& to_unregister) {
// Register patterns.
for (std::vector<const StringPattern*>::const_iterator i =
to_register.begin(); i != to_register.end(); ++i) {
DCHECK(patterns_.find((*i)->id()) == patterns_.end());
patterns_[(*i)->id()] = *i;
}
// Unregister patterns
for (std::vector<const StringPattern*>::const_iterator i =
to_unregister.begin(); i != to_unregister.end(); ++i) {
patterns_.erase((*i)->id());
}
RebuildAhoCorasickTree();
}
bool SubstringSetMatcher::Match(const std::string& text,
std::set<StringPattern::ID>* matches) const {
size_t old_number_of_matches = matches->size();
// Handle patterns matching the empty string.
matches->insert(tree_[0].matches().begin(), tree_[0].matches().end());
int current_node = 0;
size_t text_length = text.length();
for (size_t i = 0; i < text_length; ++i) {
while (!tree_[current_node].HasEdge(text[i]) && current_node != 0)
current_node = tree_[current_node].failure();
if (tree_[current_node].HasEdge(text[i])) {
current_node = tree_[current_node].GetEdge(text[i]);
matches->insert(tree_[current_node].matches().begin(),
tree_[current_node].matches().end());
} else {
DCHECK_EQ(0, current_node);
}
}
return old_number_of_matches != matches->size();
}
bool SubstringSetMatcher::IsEmpty() const {
// An empty tree consists of only the root node.
return patterns_.empty() && tree_.size() == 1u;
}
void SubstringSetMatcher::RebuildAhoCorasickTree() {
tree_.clear();
// Initialize root note of tree.
AhoCorasickNode root;
root.set_failure(0);
tree_.push_back(root);
// Insert all patterns.
for (SubstringPatternSet::const_iterator i = patterns_.begin();
i != patterns_.end(); ++i) {
InsertPatternIntoAhoCorasickTree(i->second);
}
CreateFailureEdges();
}
void SubstringSetMatcher::InsertPatternIntoAhoCorasickTree(
const StringPattern* pattern) {
const std::string& text = pattern->pattern();
size_t text_length = text.length();
// Iterators on the tree and the text.
int current_node = 0;
size_t text_pos = 0;
// Follow existing paths for as long as possible.
while (text_pos < text_length &&
tree_[current_node].HasEdge(text[text_pos])) {
current_node = tree_[current_node].GetEdge(text[text_pos]);
++text_pos;
}
// Create new nodes if necessary.
while (text_pos < text_length) {
AhoCorasickNode new_node;
tree_.push_back(new_node);
tree_[current_node].SetEdge(text[text_pos], tree_.size() - 1);
current_node = tree_.size() - 1;
++text_pos;
}
// Register match.
tree_[current_node].AddMatch(pattern->id());
}
void SubstringSetMatcher::CreateFailureEdges() {
typedef AhoCorasickNode::Edges Edges;
std::queue<int> queue;
AhoCorasickNode& root = tree_[0];
root.set_failure(0);
const AhoCorasickNode::Edges& root_edges = root.edges();
for (Edges::const_iterator e = root_edges.begin(); e != root_edges.end();
++e) {
int leads_to = e->second;
tree_[leads_to].set_failure(0);
queue.push(leads_to);
}
while (!queue.empty()) {
AhoCorasickNode& current_node = tree_[queue.front()];
queue.pop();
for (Edges::const_iterator e = current_node.edges().begin();
e != current_node.edges().end(); ++e) {
char edge_label = e->first;
int leads_to = e->second;
queue.push(leads_to);
int failure = current_node.failure();
while (!tree_[failure].HasEdge(edge_label) && failure != 0)
failure = tree_[failure].failure();
int follow_in_case_of_failure = tree_[failure].HasEdge(e->first) ?
tree_[failure].GetEdge(edge_label) : 0;
tree_[leads_to].set_failure(follow_in_case_of_failure);
tree_[leads_to].AddMatches(tree_[follow_in_case_of_failure].matches());
}
}
}
SubstringSetMatcher::AhoCorasickNode::AhoCorasickNode()
: failure_(-1) {}
SubstringSetMatcher::AhoCorasickNode::~AhoCorasickNode() {}
SubstringSetMatcher::AhoCorasickNode::AhoCorasickNode(
const SubstringSetMatcher::AhoCorasickNode& other)
: edges_(other.edges_),
failure_(other.failure_),
matches_(other.matches_) {}
SubstringSetMatcher::AhoCorasickNode&
SubstringSetMatcher::AhoCorasickNode::operator=(
const SubstringSetMatcher::AhoCorasickNode& other) {
edges_ = other.edges_;
failure_ = other.failure_;
matches_ = other.matches_;
return *this;
}
bool SubstringSetMatcher::AhoCorasickNode::HasEdge(char c) const {
return edges_.find(c) != edges_.end();
}
int SubstringSetMatcher::AhoCorasickNode::GetEdge(char c) const {
std::map<char, int>::const_iterator i = edges_.find(c);
return i == edges_.end() ? -1 : i->second;
}
void SubstringSetMatcher::AhoCorasickNode::SetEdge(char c, int node) {
edges_[c] = node;
}
void SubstringSetMatcher::AhoCorasickNode::AddMatch(StringPattern::ID id) {
matches_.insert(id);
}
void SubstringSetMatcher::AhoCorasickNode::AddMatches(
const SubstringSetMatcher::AhoCorasickNode::Matches& matches) {
matches_.insert(matches.begin(), matches.end());
}
} // namespace extensions
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