// Copyright 2021 The Dawn & Tint Authors // // Redistribution and use in source and binary forms, with or without // modification, are permitted provided that the following conditions are met: // // 1. Redistributions of source code must retain the above copyright notice, this // list of conditions and the following disclaimer. // // 2. Redistributions in binary form must reproduce the above copyright notice, // this list of conditions and the following disclaimer in the documentation // and/or other materials provided with the distribution. // // 3. Neither the name of the copyright holder nor the names of its // contributors may be used to endorse or promote products derived from // this software without specific prior written permission. // // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" // AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE // DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE // FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL // DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR // SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER // CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, // OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. #ifndef SRC_TINT_UTILS_CONTAINERS_MAP_H_ #define SRC_TINT_UTILS_CONTAINERS_MAP_H_ #include <unordered_map> namespace tint { /// Lookup is a utility function for fetching a value from an unordered map if /// it exists, otherwise returning the `if_missing` argument. /// @param map the unordered_map /// @param key the map key of the item to query /// @param if_missing the value to return if the map does not contain the given /// key. Defaults to the zero-initializer for the value type. /// @return the map item value, or `if_missing` if the map does not contain the /// given key template <typename K, typename V, typename H, typename C, typename KV = K> V Lookup(const std::unordered_map<K, V, H, C>& map, const KV& key, const V& if_missing = { … } /// GetOrAdd is a utility function for lazily adding to an unordered map. /// If the map already contains the key `key` then this is returned, otherwise /// `create()` is called and the result is added to the map and is returned. /// @param map the unordered_map /// @param key the map key of the item to query or add /// @param create a callable function-like object with the signature `V()` /// @return the value of the item with the given key, or the newly created item template <typename K, typename V, typename H, typename C, typename CREATE> V GetOrAdd(std::unordered_map<K, V, H, C>& map, const K& key, CREATE&& create) { … } } // namespace tint #endif // SRC_TINT_UTILS_CONTAINERS_MAP_H_