/** * @file lldependencies.cpp * @author Nat Goodspeed * @date 2008-09-17 * @brief Implementation for lldependencies. * * $LicenseInfo:firstyear=2008&license=viewerlgpl$ * Second Life Viewer Source Code * Copyright (C) 2010, Linden Research, Inc. * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; * version 2.1 of the License only. * * This library is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this library; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA * * Linden Research, Inc., 945 Battery Street, San Francisco, CA 94111 USA * $/LicenseInfo$ */ // Precompiled header #include "linden_common.h" // associated header #include "lldependencies.h" // STL headers #include <map> #include <sstream> // std headers // external library headers #include <boost/graph/graph_traits.hpp> // for boost::graph_traits #include <boost/graph/adjacency_list.hpp> #include <boost/graph/topological_sort.hpp> #include <boost/graph/exception.hpp> // other Linden headers #include "llexception.h" LLDependenciesBase::VertexList LLDependenciesBase::topo_sort(int vertices, const EdgeList& edges) const { // Construct a Boost Graph Library graph according to the constraints // we've collected. It seems as though we ought to be able to capture // the uniqueness of vertex keys using a setS of vertices with a // string property -- but I don't yet understand adjacency_list well // enough to get there. All the examples I've seen so far use integers // for vertices. // Define the Graph type. Use a vector for vertices so we can use the // default topological_sort vertex lookup by int index. Use a set for // edges because the same dependency may be stated twice: Node "a" may // specify that it must precede "b", while "b" may also state that it // must follow "a". typedef boost::adjacency_list<boost::setS, boost::vecS, boost::directedS, boost::no_property> Graph; // Instantiate the graph. Without vertex properties, we need say no // more about vertices than the total number. Graph g(edges.begin(), edges.end(), vertices); // topo sort typedef boost::graph_traits<Graph>::vertex_descriptor VertexDesc; typedef std::vector<VertexDesc> SortedList; SortedList sorted; // note that it throws not_a_dag if it finds a cycle try { boost::topological_sort(g, std::back_inserter(sorted)); } catch (const boost::not_a_dag& e) { // translate to the exception we define std::ostringstream out; out << "LLDependencies cycle: " << e.what() << '\n'; // Omit independent nodes: display only those that might contribute to // the cycle. describe(out, false); LLTHROW(Cycle(out.str())); } // A peculiarity of boost::topological_sort() is that it emits results in // REVERSE topological order: to get the result you want, you must // traverse the SortedList using reverse iterators. return VertexList(sorted.rbegin(), sorted.rend()); } std::ostream& LLDependenciesBase::describe(std::ostream& out, bool full) const { // Should never encounter this base-class implementation; may mean that // the KEY type doesn't have a suitable ostream operator<<(). out << "<no description available>"; return out; } std::string LLDependenciesBase::describe(bool full) const { // Just use the ostream-based describe() on a std::ostringstream. The // implementation is here mostly so that we can avoid #include <sstream> // in the header file. std::ostringstream out; describe(out, full); return out.str(); }