named_vector.h

#ifndef ALGORITHMS_NAMED_VECTOR_H
#define ALGORITHMS_NAMED_VECTOR_H
 
#include <cassert>
#include <string>
#include <vector>
 
namespace named_vector {
/*
  NamedVector is a vector-like collection with optional names
  associated with each element. It is intended for attaching names
  to objects in vectors for debugging purposes and is optimized
  to have minimal overhead when there are no names. Any name which is
  not specified is the empty string. Accessing a name with
  an invalid index will result in an error in debug mode.
 */
template <typename T>
class NamedVector {
    std::vector<T> elements;
    std::vector<std::string> names;
 
public:
    template <typename... _Args>
    T& emplace_back(_Args&&... __args)
    {
        return elements.emplace_back(std::forward<_Args>(__args)...);
    }
 
    void push_back(const T& element) { elements.push_back(element); }
 
    void push_back(T&& element) { elements.push_back(std::move(element)); }
 
    T& operator[](int index) { return elements[index]; }
 
    const T& operator[](int index) const { return elements[index]; }
 
    bool has_names() const { return !names.empty(); }
 
    void set_name(int index, const std::string& name)
    {
        assert(index >= 0 && index < size());
        int num_names = names.size();
        if (index >= num_names) {
            if (name.empty()) {
                // All unspecified names are empty by default.
                return;
            }
            names.resize(index + 1, "");
        }
        names[index] = name;
    }
 
    const std::string& get_name(int index) const
    {
        assert(index >= 0 && index < size());
        int num_names = names.size();
        if (index < num_names) {
            return names[index];
        } else {
            /*
              All unspecified names are empty by default. We use a static
              string here to avoid returning a reference to a local object.
            */
            static std::string empty;
            return empty;
        }
    }
 
    int size() const { return elements.size(); }
 
    bool empty() const { return elements.empty(); }
 
    typename std::vector<T>::reference back() { return elements.back(); }
 
    typename std::vector<T>::iterator begin() { return elements.begin(); }
 
    typename std::vector<T>::iterator end() { return elements.end(); }
 
    typename std::vector<T>::const_iterator begin() const
    {
        return elements.begin();
    }
 
    typename std::vector<T>::const_iterator end() const
    {
        return elements.end();
    }
 
    void clear()
    {
        elements.clear();
        names.clear();
    }
 
    void reserve(int capacity)
    {
        /* No space is reserved in the names vector because it is kept
           at minimal size and space is only used when necessary. */
        elements.reserve(capacity);
    }
 
    void resize(int count)
    {
        /* The names vector is not resized because it is kept
           at minimal size and only resized when necessary. */
        elements.resize(count);
    }
 
    void resize(int count, const T& value)
    {
        /* The names vector is not resized because it is kept
           at minimal size and only resized when necessary. */
        elements.resize(count, value);
    }
};
} // namespace named_vector
 
#endif