Program Listing for File map_based_queue.hpp
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#ifndef COSTMAP_QUEUE__MAP_BASED_QUEUE_HPP_
#define COSTMAP_QUEUE__MAP_BASED_QUEUE_HPP_
#include <algorithm>
#include <map>
#include <stdexcept>
#include <utility>
#include <vector>
namespace costmap_queue
{
template<class item_t>
class MapBasedQueue
{
public:
explicit MapBasedQueue(bool reset_bins = true)
: reset_bins_(reset_bins), item_count_(0)
{
reset();
}
virtual ~MapBasedQueue() = default;
virtual void reset()
{
if (reset_bins_ || item_count_ > 0) {
item_bins_.clear();
item_count_ = 0;
}
iter_ = last_insert_iter_ = item_bins_.end();
}
void enqueue(const double priority, item_t item)
{
// We keep track of the last priority we inserted. If this items priority
// matches the previous insertion we can avoid searching through all the
// bins.
if (last_insert_iter_ == item_bins_.end() || last_insert_iter_->first != priority) {
last_insert_iter_ = item_bins_.find(priority);
// If not found, create a new bin
if (last_insert_iter_ == item_bins_.end()) {
auto map_item = std::make_pair(priority, std::move(std::vector<item_t>()));
// Inserts an item if it doesn't exist. Returns an iterator to the item
// whether it existed or was inserted.
std::pair<ItemMapIterator, bool> insert_result = item_bins_.insert(std::move(map_item));
last_insert_iter_ = insert_result.first;
}
}
// Add the item to the vector for this map key
last_insert_iter_->second.push_back(item);
item_count_++;
// Use short circuiting to check if we want to update the iterator
if (iter_ == item_bins_.end() || priority < iter_->first) {
iter_ = last_insert_iter_;
}
}
bool isEmpty()
{
return item_count_ == 0;
}
item_t & front()
{
if (iter_ == item_bins_.end()) {
throw std::out_of_range("front() called on empty costmap_queue::MapBasedQueue!");
}
return iter_->second.back();
}
void pop()
{
if (iter_ != item_bins_.end() && !iter_->second.empty()) {
iter_->second.pop_back();
item_count_--;
}
auto not_empty = [](const typename ItemMap::value_type & key_val) {
return !key_val.second.empty();
};
iter_ = std::find_if(iter_, item_bins_.end(), not_empty);
}
protected:
using ItemMap = std::map<double, std::vector<item_t>>;
using ItemMapIterator = typename ItemMap::iterator;
bool reset_bins_;
ItemMap item_bins_;
unsigned int item_count_;
ItemMapIterator iter_;
ItemMapIterator last_insert_iter_;
};
} // namespace costmap_queue
#endif // COSTMAP_QUEUE__MAP_BASED_QUEUE_HPP_