json/include/nlohmann/ordered_map.hpp
2020-07-11 13:21:13 +02:00

72 lines
2.2 KiB
C++

#pragma once
#include <functional> // less
#include <memory> // allocator
#include <utility> // pair
#include <vector> // vector
namespace nlohmann
{
/// ordered_map: a minimal map-like container that preserves insertion order
/// for use within nlohmann::basic_json<ordered_map>
template <class Key, class T, class IgnoredLess = std::less<Key>,
class Allocator = std::allocator<std::pair<const Key, T>>>
struct ordered_map : std::vector<std::pair<const Key, T>, Allocator>
{
using key_type = Key;
using mapped_type = T;
using Container = std::vector<std::pair<const Key, T>, Allocator>;
using typename Container::iterator;
using typename Container::size_type;
using typename Container::value_type;
// Explicit constructors instead of `using Container::Container`
// otherwise older compilers choke on it (GCC <= 5.5, xcode <= 9.4)
ordered_map(const Allocator& alloc = Allocator()) : Container{alloc} {}
template <class It>
ordered_map(It first, It last, const Allocator& alloc = Allocator())
: Container{first, last, alloc} {}
ordered_map(std::initializer_list<T> init, const Allocator& alloc = Allocator() )
: Container{init, alloc} {}
std::pair<iterator, bool> emplace(key_type&& key, T&& t)
{
for (auto it = this->begin(); it != this->end(); ++it)
{
if (it->first == key)
{
return {it, false};
}
}
Container::emplace_back(key, t);
return {--this->end(), true};
}
T& operator[](Key&& key)
{
return emplace(std::move(key), T{}).first->second;
}
size_type erase(const Key& key)
{
for (auto it = this->begin(); it != this->end(); ++it)
{
if (it->first == key)
{
// Since we cannot move const Keys, re-construct them in place
for (auto next = it; ++next != this->end(); ++it)
{
it->~value_type(); // Destroy but keep allocation
new (&*it) value_type{std::move(*next)};
}
Container::pop_back();
return 1;
}
}
return 0;
}
};
} // namespace nlohmann