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1185d61648
A find or return-default utility. Rename `find_or_replace.h` to `map.h` which contains both these utilties that operate on maps. Change-Id: Iaa76ea3f5c5a1210e413c131dd0556c126ee5d0a Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/70521 Kokoro: Kokoro <noreply+kokoro@google.com> Reviewed-by: Antonio Maiorano <amaiorano@google.com> Commit-Queue: Ben Clayton <bclayton@google.com>
63 lines
2.3 KiB
C++
63 lines
2.3 KiB
C++
// Copyright 2021 The Tint Authors.
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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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#ifndef SRC_UTILS_MAP_H_
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#define SRC_UTILS_MAP_H_
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#include <unordered_map>
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namespace tint {
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namespace utils {
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/// Lookup is a utility function for fetching a value from an unordered map if
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/// it exists, otherwise returning the `if_missing` argument.
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/// @param map the unordered_map
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/// @param key the map key of the item to query
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/// @param if_missing the value to return if the map does not contain the given
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/// key. Defaults to the zero-initializer for the value type.
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/// @return the map item value, or `if_missing` if the map does not contain the
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/// given key
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template <typename K, typename V, typename H, typename C, typename KV = K>
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V Lookup(std::unordered_map<K, V, H, C>& map,
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const KV& key,
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const KV& if_missing = {}) {
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auto it = map.find(key);
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return it != map.end() ? it->second : if_missing;
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}
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/// GetOrCreate is a utility function for lazily adding to an unordered map.
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/// If the map already contains the key `key` then this is returned, otherwise
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/// `create()` is called and the result is added to the map and is returned.
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/// @param map the unordered_map
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/// @param key the map key of the item to query or add
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/// @param create a callable function-like object with the signature `V()`
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/// @return the value of the item with the given key, or the newly created item
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template <typename K, typename V, typename H, typename C, typename CREATE>
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V GetOrCreate(std::unordered_map<K, V, H, C>& map,
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const K& key,
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CREATE&& create) {
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auto it = map.find(key);
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if (it != map.end()) {
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return it->second;
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}
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V value = create();
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map.emplace(key, value);
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return value;
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}
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} // namespace utils
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} // namespace tint
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#endif // SRC_UTILS_MAP_H_
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