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