/*
- * Copyright 2016 Facebook, Inc.
+ * Copyright 2017 Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
#include <folly/Conv.h>
#include <folly/Optional.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 <class Map>
+template <class Map, typename Key = typename Map::key_type>
typename Map::mapped_type get_default(
- const Map& map, const typename Map::key_type& key,
- const typename Map::mapped_type& dflt =
- typename Map::mapped_type()) {
+ const Map& map,
+ const Key& key,
+ const typename Map::mapped_type& dflt = typename Map::mapped_type()) {
auto pos = map.find(key);
return (pos != map.end() ? pos->second : dflt);
}
*/
template <
class Map,
+ typename Key = typename Map::key_type,
typename Func,
typename = typename std::enable_if<std::is_convertible<
typename std::result_of<Func()>::type,
typename Map::mapped_type>::value>::type>
typename Map::mapped_type
-get_default(const Map& map, const typename Map::key_type& key, Func&& dflt) {
+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 Map::mapped_type get_or_throw(
- const Map& map, const typename Map::key_type& key,
+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()) {
* 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>
+template <class Map, typename Key = typename Map::key_type>
folly::Optional<typename Map::mapped_type> get_optional(
- const Map& map, const typename Map::key_type& key) {
+ const Map& map,
+ const Key& key) {
auto pos = map.find(key);
if (pos != map.end()) {
return folly::Optional<typename Map::mapped_type>(pos->second);
* key in the map, or the given default reference if the key doesn't exist in
* the map.
*/
-template <class Map>
+template <class Map, typename Key = typename Map::key_type>
const typename Map::mapped_type& get_ref_default(
- const Map& map, const typename Map::key_type& key,
+ 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
*/
template <
class Map,
+ typename Key = typename Map::key_type,
typename Func,
typename = typename std::enable_if<std::is_convertible<
typename std::result_of<Func()>::type,
- const typename Map::mapped_type&>::value>::type>
-const typename Map::mapped_type& get_ref_default(
- const Map& map,
- const typename Map::key_type& key,
- Func&& dflt) {
+ const typename Map::mapped_type&>::value>::type,
+ typename = typename std::enable_if<
+ std::is_reference<typename std::result_of<Func()>::type>::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>
-const typename Map::mapped_type* get_ptr(
- const Map& map, const typename Map::key_type& key) {
+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 Map::mapped_type* get_ptr(
- Map& map, const typename Map::key_type& key) {
+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...));
+}
+}
+
+/**
+ * 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
projects / folly.git / blobdiff