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// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "components/keyed_service/core/dependency_graph.h"
#include <stddef.h>
#include <algorithm>
#include <iterator>
#include <map>
#include <string_view>
#include <vector>
#include "base/containers/circular_deque.h"
#include "base/memory/raw_ptr.h"
namespace {
// Escapes |id| to be a valid ID in the DOT format [1]. This is implemented as
// enclosing the string in quotation marks, and escaping any quotation marks
// found with backslashes.
// [1] http://www.graphviz.org/content/dot-language
std::string Escape(std::string_view id) {
std::string result = "\"";
result.reserve(id.size() + 2); // +2 for the enclosing quotes.
size_t after_last_quot = 0;
size_t next_quot = id.find('"');
while (next_quot != std::string_view::npos) {
result.append(id.substr(after_last_quot, next_quot - after_last_quot));
result.append("\"");
after_last_quot = next_quot + 1;
next_quot = id.find('"', after_last_quot);
}
result.append(id.substr(after_last_quot, id.size() - after_last_quot));
result.append("\"");
return result;
}
} // namespace
DependencyGraph::DependencyGraph() = default;
DependencyGraph::~DependencyGraph() = default;
void DependencyGraph::AddNode(DependencyNode* node) {
all_nodes_.push_back(node);
construction_order_.clear();
}
void DependencyGraph::RemoveNode(DependencyNode* node) {
std::erase(all_nodes_, node);
std::erase_if(edges_, [node](const auto& edge) {
return edge.first == node || edge.second == node;
});
construction_order_.clear();
}
void DependencyGraph::AddEdge(DependencyNode* depended,
DependencyNode* dependee) {
edges_.insert(std::make_pair(depended, dependee));
construction_order_.clear();
}
bool DependencyGraph::GetConstructionOrder(
std::vector<raw_ptr<DependencyNode, VectorExperimental>>* order) {
if (construction_order_.empty() && !BuildConstructionOrder())
return false;
*order = construction_order_;
return true;
}
bool DependencyGraph::GetDestructionOrder(
std::vector<raw_ptr<DependencyNode, VectorExperimental>>* order) {
if (construction_order_.empty() && !BuildConstructionOrder())
return false;
*order = construction_order_;
// Destroy nodes in reverse order.
std::reverse(order->begin(), order->end());
return true;
}
bool DependencyGraph::BuildConstructionOrder() {
// Step 1: Build a set of nodes with no incoming edges.
base::circular_deque<DependencyNode*> queue(base::from_range, all_nodes_);
for (const auto& pair : edges_)
base::Erase(queue, pair.second);
// Step 2: Do the Kahn topological sort.
std::vector<raw_ptr<DependencyNode, VectorExperimental>> output;
EdgeMap edges(edges_);
while (!queue.empty()) {
DependencyNode* node = queue.front();
queue.pop_front();
output.push_back(node);
std::pair<EdgeMap::iterator, EdgeMap::iterator> range =
edges.equal_range(node);
auto it = range.first;
while (it != range.second) {
DependencyNode* dest = it->second;
auto temp = it;
it++;
edges.erase(temp);
bool has_incoming_edges = std::ranges::any_of(
edges, [dest](const auto& edge) { return edge.second == dest; });
if (!has_incoming_edges)
queue.push_back(dest);
}
}
if (!edges.empty()) {
// Dependency graph has a cycle.
return false;
}
construction_order_ = output;
return true;
}
std::string DependencyGraph::DumpAsGraphviz(
const std::string& toplevel_name,
const base::RepeatingCallback<std::string(DependencyNode*)>&
node_name_callback) const {
std::string result("digraph {\n");
std::string escaped_toplevel_name = Escape(toplevel_name);
// Make a copy of all nodes.
base::circular_deque<DependencyNode*> nodes(base::from_range, all_nodes_);
// State all dependencies and remove |second| so we don't generate an
// implicit dependency on the top level node.
result.append(" /* Dependencies */\n");
for (const auto& pair : edges_) {
result.append(" ");
result.append(Escape(node_name_callback.Run(pair.second)));
result.append(" -> ");
result.append(Escape(node_name_callback.Run(pair.first)));
result.append(";\n");
base::Erase(nodes, pair.second);
}
// Every node that doesn't depend on anything else will implicitly depend on
// the top level node.
result.append("\n /* Toplevel attachments */\n");
for (DependencyNode* node : nodes) {
result.append(" ");
result.append(Escape(node_name_callback.Run(node)));
result.append(" -> ");
result.append(escaped_toplevel_name);
result.append(";\n");
}
result.append("\n /* Toplevel node */\n");
result.append(" ");
result.append(escaped_toplevel_name);
result.append(" [shape=box];\n");
result.append("}\n");
return result;
}
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