1 // Copyright 2021 The Chromium Authors
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #ifndef BASE_CONTAINERS_CXX20_ERASE_LIST_H_
6 #define BASE_CONTAINERS_CXX20_ERASE_LIST_H_
7
8 #include <list>
9
10 namespace base {
11
12 // Erase/EraseIf are based on C++20's uniform container erasure API:
13 // - https://eel.is/c++draft/libraryindex#:erase
14 // - https://eel.is/c++draft/libraryindex#:erase_if
15 // They provide a generic way to erase elements from a container.
16 // The functions here implement these for the standard containers until those
17 // functions are available in the C++ standard.
18 // Note: there is no std::erase for standard associative containers so we don't
19 // have it either.
20
21 template <class T, class Allocator, class Predicate>
EraseIf(std::list<T,Allocator> & container,Predicate pred)22 size_t EraseIf(std::list<T, Allocator>& container, Predicate pred) {
23 size_t old_size = container.size();
24 container.remove_if(pred);
25 return old_size - container.size();
26 }
27
28 template <class T, class Allocator, class Value>
Erase(std::list<T,Allocator> & container,const Value & value)29 size_t Erase(std::list<T, Allocator>& container, const Value& value) {
30 // Unlike std::list::remove, this function template accepts heterogeneous
31 // types and does not force a conversion to the container's value type before
32 // invoking the == operator.
33 return EraseIf(container, [&](const T& cur) { return cur == value; });
34 }
35
36 } // namespace base
37
38 #endif // BASE_CONTAINERS_CXX20_ERASE_LIST_H_
39