我希望能够使用Boost库的read_graphml读取自定义graphml文件。但是，这要求我在读取文件时先指定属性/属性名称。
是否有办法代替列出文件中指定的属性或检查是否存在特定属性？我可能可以通过解析文件来做到这一点，但想知道是否可以通过Boost完成。
答案 0 :(得分：0)
我有以下入门概念：
#include <boost/graph/graphml.hpp>
#include <boost/core/demangle.hpp>
using namespace boost;
using Graph = adjacency_list<vecS, vecS, undirectedS>;
using Vertex = Graph::vertex_descriptor;
using Edge = Graph::edge_descriptor;
struct MyGraph {
Graph g;
dynamic_properties dp { [=](auto const&... args) { return detect_properties(dp, args...); } };
using Name = std::string;
using EdgePropMap = std::map<Edge, std::string>;
std::map<Name, std::shared_ptr<EdgePropMap> > _edge_properties;
void read(std::istream& graphml) {
::boost::read_graphml(graphml, g, dp);
}
private:
boost::shared_ptr<boost::dynamic_property_map> detect_properties(dynamic_properties& dp, Name const& name, boost::any const& key, boost::any const& value) {
auto value_type = core::demangled_name(value.type());
if (key.type() == typeid(Graph)) {
std::cout << "Vertex property: " << name << ", " << value_type << "\n" << std::flush;
//dp.property(name, boost::make_vector_property_map<Graph>(identity_property_map{}));
//return dp.lower_bound(name)->second;
}
else if (key.type() == typeid(Edge)) {
std::cout << "Edge property: " << name << ", " << value_type << "\n" << std::flush;
if (value.type() == typeid(std::string)) {
auto& map = *_edge_properties.emplace(name, std::make_shared<EdgePropMap>()).first->second;
dp.property(name, boost::make_assoc_property_map(map));
return dp.lower_bound(name)->second;
} else {
std::cerr << "Value type (" << value_type << ") not supported\n";
}
}
else if (key.type() == typeid(Vertex)) {
std::cout << "Vertex property: " << name << ", " << value_type << "\n" << std::flush;
/*if (value.type() == typeid(std::string))*/ {
dp.property(name, boost::make_vector_property_map<std::string>(get(vertex_index, g)));
return dp.lower_bound(name)->second;
}
} else {
std::cout << "Unknown property (" << core::demangled_name(key.type()) << ") " << name << ", " << value_type << "\n" << std::flush;
}
return nullptr;
}
};
int main() {
MyGraph g;
g.read(std::cin);
}
例如，在示例输入为this graphml的情况下，输出为（ Live On Coliru ）：
Vertex property: color, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >
Edge property: weight, double
Value type (double) not supported
Edge property: weight, double
Value type (double) not supported
Edge property: weight, double
Value type (double) not supported
Edge property: weight, double
Value type (double) not supported
设置边缘属性映射或当您希望使用它们支持完全不同的值类型时，会变得有些复杂。我建议使用dynamic_properties作为对动态属性映射的唯一访问权限，因为这样我们就可以使用shared_ptr to erase the mapped types of _edge_properties：
#include <boost/graph/graphml.hpp>
#include <boost/core/demangle.hpp>
using namespace boost;
using Graph = adjacency_list<vecS, vecS, undirectedS>;
using Vertex = Graph::vertex_descriptor;
using Edge = Graph::edge_descriptor;
struct MyGraph {
Graph g;
dynamic_properties dp { [=](auto const&... args) { return detect_properties(args...); } };
using Name = std::string;
std::map<Name, std::shared_ptr<void> > _edge_properties;
void read(std::istream& graphml) {
::boost::read_graphml(graphml, g, dp);
}
private:
template<typename Map>
auto add_property(const std::string& name, Map pmap)
{
boost::shared_ptr<dynamic_property_map> pm(
boost::static_pointer_cast<dynamic_property_map>(
boost::make_shared<detail::dynamic_property_map_adaptor<Map> >(pmap)));
dp.insert(name, pm);
return pm;
}
template <typename V>
auto add_edge_property(std::string const& name) {
auto map = std::make_shared<std::map<Edge, V> >();
_edge_properties.emplace(name, map);
return add_property(name, boost::make_assoc_property_map(*map));
}
template <typename V>
auto add_vertex_property(std::string const& name) {
// NOTE, if vertex_index isn't present you might want to use
// make_assoc_property_map as with the edge properties
return add_property(name, boost::make_vector_property_map<V>(get(vertex_index, g)));
}
boost::shared_ptr<dynamic_property_map> detect_properties(Name const& name, boost::any const& key, boost::any const& value) {
auto value_type = core::demangled_name(value.type());
if (key.type() == typeid(Graph)) {
std::cout << "Graph property detected: " << name << ", " << value_type << "\n" << std::flush;
//dp.property(name, boost::make_vector_property_map<Graph>(identity_property_map{}));
//return dp.lower_bound(name)->second;
}
else if (key.type() == typeid(Edge)) {
std::cout << "Edge property detected: " << name << ", " << value_type << "\n" << std::flush;
if (value.type() == typeid(std::string)) {
return add_edge_property<std::string>(name);
} else if (value.type() == typeid(double)) {
return add_edge_property<double>(name);
} else {
std::cerr << "Value type (" << value_type << ") not supported\n";
}
}
else if (key.type() == typeid(Vertex)) {
std::cout << "Vertex property detected: " << name << ", " << value_type << "\n" << std::flush;
if (value.type() == typeid(std::string)) {
return add_vertex_property<std::string>(name);
} else if (value.type() == typeid(double)) {
return add_vertex_property<double>(name);
} else {
std::cerr << "Value type (" << value_type << ") not supported\n";
}
} else {
std::cout << "Unknown property (" << core::demangled_name(key.type()) << ") " << name << ", " << value_type << "\n" << std::flush;
}
return nullptr;
}
};
int main() {
MyGraph g;
g.read(std::cin);
}
现在打印：
Vertex property detected: color, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >
Edge property detected: weight, double
第二个版本实际上要安全得多，因为第一个版本“误用” lower_bound可以查找刚刚按名称添加的属性。如果存在具有相同名称的Edge / Vertex属性 ，则可能破坏。
第二个版本添加了一个辅助功能，可以避免这种不准确性（add_property）。