308 lines
9.6 KiB
C++
308 lines
9.6 KiB
C++
/*
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* Copyright 2012-present Facebook, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#pragma once
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#include <folly/Conv.h>
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#include <folly/Optional.h>
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#include <folly/functional/Invoke.h>
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#include <tuple>
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namespace folly {
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/**
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* Given a map and a key, return the value corresponding to the key in the map,
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* or a given default value if the key doesn't exist in the map.
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*/
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template <typename Map, typename Key>
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typename Map::mapped_type get_default(const Map& map, const Key& key) {
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auto pos = map.find(key);
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return (pos != map.end()) ? (pos->second) : (typename Map::mapped_type{});
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}
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template <
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class Map,
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typename Key = typename Map::key_type,
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typename Value = typename Map::mapped_type,
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typename std::enable_if<!is_invocable<Value>::value>::type* = nullptr>
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typename Map::mapped_type
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get_default(const Map& map, const Key& key, Value&& dflt) {
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using M = typename Map::mapped_type;
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auto pos = map.find(key);
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return (pos != map.end()) ? (pos->second) : M(std::forward<Value>(dflt));
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}
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/**
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* Give a map and a key, return the value corresponding to the key in the map,
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* or a given default value if the key doesn't exist in the map.
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*/
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template <
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class Map,
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typename Key = typename Map::key_type,
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typename Func,
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typename = typename std::enable_if<
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is_invocable_r<typename Map::mapped_type, Func>::value>::type>
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typename Map::mapped_type
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get_default(const Map& map, const Key& key, Func&& dflt) {
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auto pos = map.find(key);
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return pos != map.end() ? pos->second : dflt();
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}
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/**
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* Given a map and a key, return the value corresponding to the key in the map,
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* or throw an exception of the specified type.
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*/
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template <
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class E = std::out_of_range,
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class Map,
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typename Key = typename Map::key_type>
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const typename Map::mapped_type& get_or_throw(
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const Map& map,
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const Key& key,
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const std::string& exceptionStrPrefix = std::string()) {
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auto pos = map.find(key);
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if (pos != map.end()) {
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return pos->second;
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}
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throw E(folly::to<std::string>(exceptionStrPrefix, key));
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}
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template <
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class E = std::out_of_range,
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class Map,
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typename Key = typename Map::key_type>
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typename Map::mapped_type& get_or_throw(
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Map& map,
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const Key& key,
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const std::string& exceptionStrPrefix = std::string()) {
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auto pos = map.find(key);
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if (pos != map.end()) {
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return pos->second;
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}
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throw E(folly::to<std::string>(exceptionStrPrefix, key));
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}
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/**
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* Given a map and a key, return a Optional<V> if the key exists and None if the
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* key does not exist in the map.
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*/
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template <class Map, typename Key = typename Map::key_type>
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folly::Optional<typename Map::mapped_type> get_optional(
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const Map& map,
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const Key& key) {
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auto pos = map.find(key);
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if (pos != map.end()) {
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return folly::Optional<typename Map::mapped_type>(pos->second);
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} else {
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return folly::none;
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}
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}
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/**
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* Given a map and a key, return a reference to the value corresponding to the
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* key in the map, or the given default reference if the key doesn't exist in
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* the map.
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*/
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template <class Map, typename Key = typename Map::key_type>
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const typename Map::mapped_type& get_ref_default(
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const Map& map,
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const Key& key,
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const typename Map::mapped_type& dflt) {
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auto pos = map.find(key);
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return (pos != map.end() ? pos->second : dflt);
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}
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/**
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* Passing a temporary default value returns a dangling reference when it is
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* returned. Lifetime extension is broken by the indirection.
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* The caller must ensure that the default value outlives the reference returned
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* by get_ref_default().
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*/
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template <class Map, typename Key = typename Map::key_type>
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const typename Map::mapped_type& get_ref_default(
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const Map& map,
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const Key& key,
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typename Map::mapped_type&& dflt) = delete;
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template <class Map, typename Key = typename Map::key_type>
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const typename Map::mapped_type& get_ref_default(
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const Map& map,
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const Key& key,
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const typename Map::mapped_type&& dflt) = delete;
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/**
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* Given a map and a key, return a reference to the value corresponding to the
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* key in the map, or the given default reference if the key doesn't exist in
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* the map.
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*/
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template <
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class Map,
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typename Key = typename Map::key_type,
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typename Func,
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typename = typename std::enable_if<
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is_invocable_r<const typename Map::mapped_type&, Func>::value>::type,
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typename = typename std::enable_if<
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std::is_reference<invoke_result_t<Func>>::value>::type>
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const typename Map::mapped_type&
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get_ref_default(const Map& map, const Key& key, Func&& dflt) {
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auto pos = map.find(key);
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return (pos != map.end() ? pos->second : dflt());
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}
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/**
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* Given a map and a key, return a pointer to the value corresponding to the
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* key in the map, or nullptr if the key doesn't exist in the map.
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*/
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template <class Map, typename Key = typename Map::key_type>
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const typename Map::mapped_type* get_ptr(const Map& map, const Key& key) {
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auto pos = map.find(key);
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return (pos != map.end() ? &pos->second : nullptr);
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}
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/**
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* Non-const overload of the above.
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*/
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template <class Map, typename Key = typename Map::key_type>
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typename Map::mapped_type* get_ptr(Map& map, const Key& key) {
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auto pos = map.find(key);
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return (pos != map.end() ? &pos->second : nullptr);
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}
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// TODO: Remove the return type computations when clang 3.5 and gcc 5.1 are
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// the minimum supported versions.
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namespace detail {
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template <
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class T,
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size_t pathLength,
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class = typename std::enable_if<(pathLength > 0)>::type>
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struct NestedMapType {
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using type = typename NestedMapType<T, pathLength - 1>::type::mapped_type;
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};
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template <class T>
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struct NestedMapType<T, 1> {
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using type = typename T::mapped_type;
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};
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template <typename... KeysDefault>
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struct DefaultType;
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template <typename Default>
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struct DefaultType<Default> {
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using type = Default;
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};
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template <typename Key, typename... KeysDefault>
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struct DefaultType<Key, KeysDefault...> {
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using type = typename DefaultType<KeysDefault...>::type;
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};
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template <class... KeysDefault>
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auto extract_default(const KeysDefault&... keysDefault) ->
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typename DefaultType<KeysDefault...>::type const& {
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return std::get<sizeof...(KeysDefault) - 1>(std::tie(keysDefault...));
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}
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} // namespace detail
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/**
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* Given a map of maps and a path of keys, return a Optional<V> if the nested
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* key exists and None if the nested keys does not exist in the map.
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*/
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template <class Map, class Key1, class Key2, class... Keys>
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auto get_optional(
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const Map& map,
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const Key1& key1,
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const Key2& key2,
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const Keys&... keys)
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-> folly::Optional<
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typename detail::NestedMapType<Map, 2 + sizeof...(Keys)>::type> {
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auto pos = map.find(key1);
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return pos != map.end() ? get_optional(pos->second, key2, keys...)
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: folly::none;
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}
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/**
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* Given a map of maps and a path of keys, return a pointer to the nested value,
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* or nullptr if the key doesn't exist in the map.
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*/
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template <class Map, class Key1, class Key2, class... Keys>
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auto get_ptr(
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const Map& map,
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const Key1& key1,
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const Key2& key2,
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const Keys&... keys) ->
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typename detail::NestedMapType<Map, 2 + sizeof...(Keys)>::type const* {
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auto pos = map.find(key1);
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return pos != map.end() ? get_ptr(pos->second, key2, keys...) : nullptr;
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}
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template <class Map, class Key1, class Key2, class... Keys>
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auto get_ptr(Map& map, const Key1& key1, const Key2& key2, const Keys&... keys)
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-> typename detail::NestedMapType<Map, 2 + sizeof...(Keys)>::type* {
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auto pos = map.find(key1);
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return pos != map.end() ? get_ptr(pos->second, key2, keys...) : nullptr;
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}
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/**
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* Given a map and a path of keys, return the value corresponding to the nested
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* value, or a given default value if the path doesn't exist in the map.
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* The default value is the last parameter, and is copied when returned.
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*/
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template <
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class Map,
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class Key1,
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class Key2,
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class... KeysDefault,
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typename = typename std::enable_if<sizeof...(KeysDefault) != 0>::type>
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auto get_default(
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const Map& map,
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const Key1& key1,
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const Key2& key2,
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const KeysDefault&... keysDefault) ->
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typename detail::NestedMapType<Map, 1 + sizeof...(KeysDefault)>::type {
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if (const auto* ptr = get_ptr(map, key1)) {
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return get_default(*ptr, key2, keysDefault...);
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}
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return detail::extract_default(keysDefault...);
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}
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/**
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* Given a map and a path of keys, return a reference to the value corresponding
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* to the nested value, or the given default reference if the path doesn't exist
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* in the map.
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* The default value is the last parameter, and must be a lvalue reference.
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*/
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template <
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class Map,
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class Key1,
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class Key2,
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class... KeysDefault,
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typename = typename std::enable_if<sizeof...(KeysDefault) != 0>::type,
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typename = typename std::enable_if<std::is_lvalue_reference<
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typename detail::DefaultType<KeysDefault...>::type>::value>::type>
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auto get_ref_default(
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const Map& map,
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const Key1& key1,
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const Key2& key2,
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KeysDefault&&... keysDefault) ->
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typename detail::NestedMapType<Map, 1 + sizeof...(KeysDefault)>::type
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const& {
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if (const auto* ptr = get_ptr(map, key1)) {
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return get_ref_default(*ptr, key2, keysDefault...);
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}
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return detail::extract_default(keysDefault...);
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}
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} // namespace folly
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