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// Copyright 2020 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef BASE_CONTAINERS_FIXED_FLAT_MAP_H_
#define BASE_CONTAINERS_FIXED_FLAT_MAP_H_
#include <algorithm>
#include <array>
#include <functional>
#include <utility>
#include "base/containers/flat_map.h"
#include "base/containers/flat_tree.h"
namespace base {
namespace internal {
// Not constexpr to trigger a compile error.
void FixedFlatMapInputNotSortedOrNotUnique();
} // namespace internal
// fixed_flat_map is a immutable container with a std::map-like interface that
// stores its contents in a sorted std::array.
//
// It is a special case of base::flat_map, and mostly useful as a look-up table.
//
// Please see //base/containers/README.md for an overview of which container
// to select.
//
// QUICK REFERENCE
//
// Most of the core functionality is inherited from flat_tree. Please see
// flat_tree.h for more details for most of these functions. As a quick
// reference, the functions available are:
//
// Constructors (inputs need to be sorted):
// fixed_flat_map(const fixed_flat_map&);
// fixed_flat_map(sorted_unique_t,
// const container_type& items,
// const Compare& compare = Compare());
//
// Size management functions:
// size_t size() const;
// size_t max_size() const;
// bool empty() const;
//
// Iterator functions:
// iterator begin();
// const_iterator begin() const;
// const_iterator cbegin() const;
// iterator end();
// const_iterator end() const;
// const_iterator cend() const;
// reverse_iterator rbegin();
// const reverse_iterator rbegin() const;
// const_reverse_iterator crbegin() const;
// reverse_iterator rend();
// const_reverse_iterator rend() const;
// const_reverse_iterator crend() const;
//
// Insert and accessor functions:
// mapped_type& at(const K&);
// const mapped_type& at(const K&) const;
// Comparators (see std::map documentation).
// key_compare key_comp() const;
// value_compare value_comp() const;
//
// Search functions:
// template <typename K> size_t count(const K&) const;
// template <typename K> iterator find(const K&);
// template <typename K> const_iterator find(const K&) const;
// template <typename K> bool contains(const K&) const;
// template <typename K>
// pair<iterator, iterator> equal_range(const K&);
// template <typename K>
// pair<const_iterator, const_iterator> equal_range(K&) const;
// template <typename K> iterator lower_bound(const K&);
// template <typename K> const_iterator lower_bound(const K&) const;
// template <typename K> iterator upper_bound(const K&);
// template <typename K> const_iterator upper_bound(const K&) const;
//
// Non-member operators:
// bool operator==(const fixed_flat_map&, const fixed_flat_map&);
// bool operator!=(const fixed_flat_map&, const fixed_flat_map&);
// bool operator<(const fixed_flat_map&, const fixed_flat_map&);
// bool operator>(const fixed_flat_map&, const fixed_flat_map&);
// bool operator>=(const fixed_flat_map&, const fixed_flat_map&);
// bool operator<=(const fixed_flat_map&, const fixed_flat_map&);
//
template <class Key, class Mapped, size_t N, class Compare = std::less<>>
using fixed_flat_map = base::
flat_map<Key, Mapped, Compare, std::array<std::pair<const Key, Mapped>, N>>;
// Utility function to simplify constructing a fixed_flat_map from a fixed list
// of keys and values. Requires that the passed in `data` contains unique keys.
//
// Large inputs will run into compiler limits, e.g. "constexpr evaluation hit
// maximum step limit", unless `data` is already sorted.
//
// Example usage:
// constexpr auto kMap = base::MakeFixedFlatMap<std::string_view, int>(
// {{"foo", 1}, {"bar", 2}, {"baz", 3}});
template <class Key, class Mapped, class Compare = std::less<>, size_t N>
consteval fixed_flat_map<Key, Mapped, N, Compare> MakeFixedFlatMap(
std::pair<Key, Mapped> (&&data)[N],
const Compare& comp = Compare()) {
using FixedFlatMap = fixed_flat_map<Key, Mapped, N, Compare>;
typename FixedFlatMap::value_compare value_comp{comp};
if (!internal::is_sorted_and_unique(data, value_comp)) {
std::ranges::sort(data, value_comp);
if (!internal::is_sorted_and_unique(data, value_comp)) {
internal::FixedFlatMapInputNotSortedOrNotUnique();
}
}
return FixedFlatMap(
sorted_unique, internal::ToArray<typename FixedFlatMap::value_type>(data),
comp);
}
} // namespace base
#endif // BASE_CONTAINERS_FIXED_FLAT_MAP_H_
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