osrm-backend/include/util/static_graph.hpp

#ifndef STATIC_GRAPH_HPP
#define STATIC_GRAPH_HPP

#include "util/integer_range.hpp"
#include "util/percent.hpp"
#include "util/shared_memory_vector_wrapper.hpp"
#include "util/typedefs.hpp"

#include <boost/assert.hpp>

#include <algorithm>
#include <limits>
#include <utility>
#include <vector>

namespace osrm
{
namespace util
{

template <typename EdgeDataT, bool UseSharedMemory = false> class StaticGraph
{
  public:
    using NodeIterator = NodeID;
    using EdgeIterator = NodeID;
    using EdgeData = EdgeDataT;
    using EdgeRange = range<EdgeIterator>;

    class InputEdge
    {
      public:
        NodeIterator source;
        NodeIterator target;
        EdgeDataT data;

        template <typename... Ts>
        InputEdge(NodeIterator source, NodeIterator target, Ts &&... data)
            : source(source), target(target), data(std::forward<Ts>(data)...)
        {
        }
        bool operator<(const InputEdge &right) const
        {
            if (source != right.source)
            {
                return source < right.source;
            }
            return target < right.target;
        }
    };

    struct NodeArrayEntry
    {
        // index of the first edge
        EdgeIterator first_edge;
    };

    struct EdgeArrayEntry
    {
        NodeID target;
        EdgeDataT data;
    };

    EdgeRange GetAdjacentEdgeRange(const NodeID node) const
    {
        return irange(BeginEdges(node), EndEdges(node));
    }

    template <typename ContainerT> StaticGraph(const int nodes, const ContainerT &graph)
    {
        BOOST_ASSERT(std::is_sorted(const_cast<ContainerT &>(graph).begin(),
                                    const_cast<ContainerT &>(graph).end()));

        number_of_nodes = nodes;
        number_of_edges = static_cast<EdgeIterator>(graph.size());
        node_array.resize(number_of_nodes + 1);
        EdgeIterator edge = 0;
        EdgeIterator position = 0;
        for (const auto node : irange(0u, number_of_nodes + 1))
        {
            EdgeIterator last_edge = edge;
            while (edge < number_of_edges && graph[edge].source == node)
            {
                ++edge;
            }
            node_array[node].first_edge = position; //=edge
            position += edge - last_edge;           // remove
        }
        edge_array.resize(position); //(edge)
        edge = 0;
        for (const auto node : irange(0u, number_of_nodes))
        {
            EdgeIterator e = node_array[node + 1].first_edge;
            for (const auto i : irange(node_array[node].first_edge, e))
            {
                edge_array[i].target = graph[edge].target;
                edge_array[i].data = graph[edge].data;
                edge++;
            }
        }
    }

    StaticGraph(typename ShM<NodeArrayEntry, UseSharedMemory>::vector &nodes,
                typename ShM<EdgeArrayEntry, UseSharedMemory>::vector &edges)
    {
        number_of_nodes = static_cast<decltype(number_of_nodes)>(nodes.size() - 1);
        number_of_edges = static_cast<decltype(number_of_edges)>(edges.size());

        using std::swap;
        swap(node_array, nodes);
        swap(edge_array, edges);
    }

    unsigned GetNumberOfNodes() const { return number_of_nodes; }

    unsigned GetNumberOfEdges() const { return number_of_edges; }

    unsigned GetOutDegree(const NodeIterator n) const { return EndEdges(n) - BeginEdges(n); }

    inline NodeIterator GetTarget(const EdgeIterator e) const
    {
        return NodeIterator(edge_array[e].target);
    }

    EdgeDataT &GetEdgeData(const EdgeIterator e) { return edge_array[e].data; }

    const EdgeDataT &GetEdgeData(const EdgeIterator e) const { return edge_array[e].data; }

    EdgeIterator BeginEdges(const NodeIterator n) const
    {
        return EdgeIterator(node_array.at(n).first_edge);
    }

    EdgeIterator EndEdges(const NodeIterator n) const
    {
        return EdgeIterator(node_array.at(n + 1).first_edge);
    }

    // searches for a specific edge
    EdgeIterator FindEdge(const NodeIterator from, const NodeIterator to) const
    {
        for (const auto i : irange(BeginEdges(from), EndEdges(from)))
        {
            if (to == edge_array[i].target)
            {
                return i;
            }
        }
        return SPECIAL_EDGEID;
    }

    /**
     * Finds the edge with the smallest `.distance` going from `from` to `to`
     * @param from the source node ID
     * @param to the target node ID
     * @param filter a functor that returns a `bool` that determines whether an edge should be
     * tested or not.
     *   Takes `EdgeData` as a parameter.
     * @return the ID of the smallest edge if any were found that satisfied *filter*, or
     * `SPECIAL_EDGEID` if no
     *   matching edge is found.
     */
    template <typename FilterFunction>
    EdgeIterator
    FindSmallestEdge(const NodeIterator from, const NodeIterator to, FilterFunction &&filter) const
    {
        EdgeIterator smallest_edge = SPECIAL_EDGEID;
        EdgeWeight smallest_weight = INVALID_EDGE_WEIGHT;
        for (auto edge : GetAdjacentEdgeRange(from))
        {
            const NodeID target = GetTarget(edge);
            const auto &data = GetEdgeData(edge);
            if (target == to && data.distance < smallest_weight &&
                std::forward<FilterFunction>(filter)(data))
            {
                smallest_edge = edge;
                smallest_weight = data.distance;
            }
        }
        return smallest_edge;
    }

    EdgeIterator FindEdgeInEitherDirection(const NodeIterator from, const NodeIterator to) const
    {
        EdgeIterator tmp = FindEdge(from, to);
        return (SPECIAL_NODEID != tmp ? tmp : FindEdge(to, from));
    }

    EdgeIterator
    FindEdgeIndicateIfReverse(const NodeIterator from, const NodeIterator to, bool &result) const
    {
        EdgeIterator current_iterator = FindEdge(from, to);
        if (SPECIAL_NODEID == current_iterator)
        {
            current_iterator = FindEdge(to, from);
            if (SPECIAL_NODEID != current_iterator)
            {
                result = true;
            }
        }
        return current_iterator;
    }

  private:
    NodeIterator number_of_nodes;
    EdgeIterator number_of_edges;

    typename ShM<NodeArrayEntry, UseSharedMemory>::vector node_array;
    typename ShM<EdgeArrayEntry, UseSharedMemory>::vector edge_array;
};
}
}

#endif // STATIC_GRAPH_HPP