132 lines
3.5 KiB
C++
132 lines
3.5 KiB
C++
/*
|
|
* Copyright (C) 2016 The Android Open Source Project
|
|
*
|
|
* Licensed under the Apache License, Version 2.0 (the "License");
|
|
* you may not use this file except in compliance with the License.
|
|
* You may obtain a copy of the License at
|
|
*
|
|
* http://www.apache.org/licenses/LICENSE-2.0
|
|
*
|
|
* Unless required by applicable law or agreed to in writing, software
|
|
* distributed under the License is distributed on an "AS IS" BASIS,
|
|
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
* See the License for the specific language governing permissions and
|
|
* limitations under the License.
|
|
*/
|
|
|
|
// Based on system/update_engine/payload_generator/tarjan.cc
|
|
|
|
#ifndef LIBMEMUNREACHABLE_TARJAN_H_
|
|
#define LIBMEMUNREACHABLE_TARJAN_H_
|
|
|
|
#include <assert.h>
|
|
#include <algorithm>
|
|
|
|
#include "Allocator.h"
|
|
|
|
template<class T>
|
|
class Node {
|
|
public:
|
|
allocator::set<Node<T>*> references_in;
|
|
allocator::set<Node<T>*> references_out;
|
|
size_t index;
|
|
size_t lowlink;
|
|
|
|
T* ptr;
|
|
|
|
Node(T* ptr, Allocator<Node> allocator) : references_in(allocator), references_out(allocator),
|
|
ptr(ptr) {};
|
|
Node(Node&& rhs) = default;
|
|
void Edge(Node<T>* ref) {
|
|
references_out.emplace(ref);
|
|
ref->references_in.emplace(this);
|
|
}
|
|
template<class F>
|
|
void Foreach(F&& f) {
|
|
for (auto& node: references_out) {
|
|
f(node->ptr);
|
|
}
|
|
}
|
|
private:
|
|
DISALLOW_COPY_AND_ASSIGN(Node<T>);
|
|
};
|
|
|
|
template<class T>
|
|
using Graph = allocator::vector<Node<T>*>;
|
|
|
|
template<class T>
|
|
using SCC = allocator::vector<Node<T>*>;
|
|
|
|
template<class T>
|
|
using SCCList = allocator::vector<SCC<T>>;
|
|
|
|
template<class T>
|
|
class TarjanAlgorithm {
|
|
public:
|
|
explicit TarjanAlgorithm(Allocator<void> allocator) : index_(0),
|
|
stack_(allocator), components_(allocator) {}
|
|
|
|
void Execute(Graph<T>& graph, SCCList<T>& out);
|
|
private:
|
|
static constexpr size_t UNDEFINED_INDEX = static_cast<size_t>(-1);
|
|
void Tarjan(Node<T>* vertex, Graph<T>& graph);
|
|
|
|
size_t index_;
|
|
allocator::vector<Node<T>*> stack_;
|
|
SCCList<T> components_;
|
|
};
|
|
|
|
template<class T>
|
|
void TarjanAlgorithm<T>::Execute(Graph<T>& graph, SCCList<T>& out) {
|
|
stack_.clear();
|
|
components_.clear();
|
|
index_ = 0;
|
|
for (auto& it: graph) {
|
|
it->index = UNDEFINED_INDEX;
|
|
it->lowlink = UNDEFINED_INDEX;
|
|
}
|
|
|
|
for (auto& it: graph) {
|
|
if (it->index == UNDEFINED_INDEX) {
|
|
Tarjan(it, graph);
|
|
}
|
|
}
|
|
out.swap(components_);
|
|
}
|
|
|
|
template<class T>
|
|
void TarjanAlgorithm<T>::Tarjan(Node<T>* vertex, Graph<T>& graph) {
|
|
assert(vertex->index == UNDEFINED_INDEX);
|
|
vertex->index = index_;
|
|
vertex->lowlink = index_;
|
|
index_++;
|
|
stack_.push_back(vertex);
|
|
for (auto& it: vertex->references_out) {
|
|
Node<T>* vertex_next = it;
|
|
if (vertex_next->index == UNDEFINED_INDEX) {
|
|
Tarjan(vertex_next, graph);
|
|
vertex->lowlink = std::min(vertex->lowlink, vertex_next->lowlink);
|
|
} else if (std::find(stack_.begin(), stack_.end(), vertex_next) != stack_.end()) {
|
|
vertex->lowlink = std::min(vertex->lowlink, vertex_next->index);
|
|
}
|
|
}
|
|
if (vertex->lowlink == vertex->index) {
|
|
SCC<T> component{components_.get_allocator()};
|
|
Node<T>* other_vertex;
|
|
do {
|
|
other_vertex = stack_.back();
|
|
stack_.pop_back();
|
|
component.push_back(other_vertex);
|
|
} while (other_vertex != vertex && !stack_.empty());
|
|
|
|
components_.emplace_back(component);
|
|
}
|
|
}
|
|
|
|
template<class T>
|
|
void Tarjan(Graph<T>& graph, SCCList<T>& out) {
|
|
TarjanAlgorithm<T> tarjan{graph.get_allocator()};
|
|
tarjan.Execute(graph, out);
|
|
}
|
|
|
|
#endif // LIBMEMUNREACHABLE_TARJAN_H_
|