707 lines
25 KiB
C++
707 lines
25 KiB
C++
// Copyright (c) 2011 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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// Derived from google3/util/gtl/stl_util.h
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#ifndef BASE_STL_UTIL_H_
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#define BASE_STL_UTIL_H_
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#include <algorithm>
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#include <deque>
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#include <forward_list>
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#include <functional>
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#include <initializer_list>
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#include <iterator>
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#include <list>
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#include <map>
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#include <set>
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#include <string>
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#include <type_traits>
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#include <unordered_map>
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#include <unordered_set>
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#include <utility>
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#include <vector>
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#include "base/logging.h"
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#include "base/optional.h"
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#include "base/template_util.h"
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namespace base {
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namespace internal {
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// Calls erase on iterators of matching elements and returns the number of
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// removed elements.
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template <typename Container, typename Predicate>
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size_t IterateAndEraseIf(Container& container, Predicate pred) {
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size_t old_size = container.size();
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for (auto it = container.begin(), last = container.end(); it != last;) {
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if (pred(*it))
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it = container.erase(it);
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else
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++it;
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}
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return old_size - container.size();
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}
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template <typename Iter>
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constexpr bool IsRandomAccessIter =
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std::is_same<typename std::iterator_traits<Iter>::iterator_category,
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std::random_access_iterator_tag>::value;
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// Utility type traits used for specializing base::Contains() below.
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template <typename Container, typename Element, typename = void>
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struct HasFindWithNpos : std::false_type {};
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template <typename Container, typename Element>
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struct HasFindWithNpos<
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Container,
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Element,
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void_t<decltype(std::declval<const Container&>().find(
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std::declval<const Element&>()) != Container::npos)>>
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: std::true_type {};
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template <typename Container, typename Element, typename = void>
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struct HasFindWithEnd : std::false_type {};
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template <typename Container, typename Element>
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struct HasFindWithEnd<Container,
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Element,
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void_t<decltype(std::declval<const Container&>().find(
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std::declval<const Element&>()) !=
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std::declval<const Container&>().end())>>
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: std::true_type {};
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template <typename Container, typename Element, typename = void>
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struct HasContains : std::false_type {};
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template <typename Container, typename Element>
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struct HasContains<Container,
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Element,
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void_t<decltype(std::declval<const Container&>().contains(
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std::declval<const Element&>()))>> : std::true_type {};
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} // namespace internal
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// C++14 implementation of C++17's std::size():
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// http://en.cppreference.com/w/cpp/iterator/size
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template <typename Container>
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constexpr auto size(const Container& c) -> decltype(c.size()) {
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return c.size();
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}
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template <typename T, size_t N>
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constexpr size_t size(const T (&array)[N]) noexcept {
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return N;
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}
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// C++14 implementation of C++17's std::empty():
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// http://en.cppreference.com/w/cpp/iterator/empty
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template <typename Container>
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constexpr auto empty(const Container& c) -> decltype(c.empty()) {
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return c.empty();
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}
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template <typename T, size_t N>
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constexpr bool empty(const T (&array)[N]) noexcept {
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return false;
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}
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template <typename T>
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constexpr bool empty(std::initializer_list<T> il) noexcept {
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return il.size() == 0;
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}
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// C++14 implementation of C++17's std::data():
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// http://en.cppreference.com/w/cpp/iterator/data
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template <typename Container>
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constexpr auto data(Container& c) -> decltype(c.data()) {
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return c.data();
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}
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// std::basic_string::data() had no mutable overload prior to C++17 [1].
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// Hence this overload is provided.
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// Note: str[0] is safe even for empty strings, as they are guaranteed to be
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// null-terminated [2].
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//
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// [1] http://en.cppreference.com/w/cpp/string/basic_string/data
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// [2] http://en.cppreference.com/w/cpp/string/basic_string/operator_at
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template <typename CharT, typename Traits, typename Allocator>
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CharT* data(std::basic_string<CharT, Traits, Allocator>& str) {
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return std::addressof(str[0]);
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}
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template <typename Container>
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constexpr auto data(const Container& c) -> decltype(c.data()) {
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return c.data();
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}
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template <typename T, size_t N>
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constexpr T* data(T (&array)[N]) noexcept {
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return array;
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}
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template <typename T>
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constexpr const T* data(std::initializer_list<T> il) noexcept {
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return il.begin();
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}
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// std::array::data() was not constexpr prior to C++17 [1].
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// Hence these overloads are provided.
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//
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// [1] https://en.cppreference.com/w/cpp/container/array/data
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template <typename T, size_t N>
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constexpr T* data(std::array<T, N>& array) noexcept {
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return !array.empty() ? &array[0] : nullptr;
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}
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template <typename T, size_t N>
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constexpr const T* data(const std::array<T, N>& array) noexcept {
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return !array.empty() ? &array[0] : nullptr;
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}
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// C++14 implementation of C++17's std::as_const():
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// https://en.cppreference.com/w/cpp/utility/as_const
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template <typename T>
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constexpr std::add_const_t<T>& as_const(T& t) noexcept {
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return t;
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}
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template <typename T>
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void as_const(const T&& t) = delete;
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// Returns a const reference to the underlying container of a container adapter.
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// Works for std::priority_queue, std::queue, and std::stack.
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template <class A>
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const typename A::container_type& GetUnderlyingContainer(const A& adapter) {
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struct ExposedAdapter : A {
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using A::c;
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};
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return adapter.*&ExposedAdapter::c;
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}
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// Clears internal memory of an STL object.
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// STL clear()/reserve(0) does not always free internal memory allocated
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// This function uses swap/destructor to ensure the internal memory is freed.
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template<class T>
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void STLClearObject(T* obj) {
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T tmp;
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tmp.swap(*obj);
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// Sometimes "T tmp" allocates objects with memory (arena implementation?).
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// Hence using additional reserve(0) even if it doesn't always work.
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obj->reserve(0);
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}
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// Counts the number of instances of val in a container.
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template <typename Container, typename T>
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typename std::iterator_traits<
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typename Container::const_iterator>::difference_type
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STLCount(const Container& container, const T& val) {
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return std::count(container.begin(), container.end(), val);
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}
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// General purpose implementation to check if |container| contains |value|.
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template <typename Container,
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typename Value,
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std::enable_if_t<
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!internal::HasFindWithNpos<Container, Value>::value &&
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!internal::HasFindWithEnd<Container, Value>::value &&
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!internal::HasContains<Container, Value>::value>* = nullptr>
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bool Contains(const Container& container, const Value& value) {
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using std::begin;
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using std::end;
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return std::find(begin(container), end(container), value) != end(container);
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}
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// Specialized Contains() implementation for when |container| has a find()
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// member function and a static npos member, but no contains() member function.
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template <typename Container,
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typename Value,
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std::enable_if_t<internal::HasFindWithNpos<Container, Value>::value &&
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!internal::HasContains<Container, Value>::value>* =
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nullptr>
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bool Contains(const Container& container, const Value& value) {
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return container.find(value) != Container::npos;
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}
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// Specialized Contains() implementation for when |container| has a find()
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// and end() member function, but no contains() member function.
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template <typename Container,
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typename Value,
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std::enable_if_t<internal::HasFindWithEnd<Container, Value>::value &&
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!internal::HasContains<Container, Value>::value>* =
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nullptr>
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bool Contains(const Container& container, const Value& value) {
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return container.find(value) != container.end();
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}
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// Specialized Contains() implementation for when |container| has a contains()
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// member function.
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template <
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typename Container,
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typename Value,
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std::enable_if_t<internal::HasContains<Container, Value>::value>* = nullptr>
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bool Contains(const Container& container, const Value& value) {
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return container.contains(value);
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}
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// O(1) implementation of const casting an iterator for any sequence,
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// associative or unordered associative container in the STL.
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//
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// Reference: https://stackoverflow.com/a/10669041
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template <typename Container,
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typename ConstIter,
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std::enable_if_t<!internal::IsRandomAccessIter<ConstIter>>* = nullptr>
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constexpr auto ConstCastIterator(Container& c, ConstIter it) {
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return c.erase(it, it);
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}
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// Explicit overload for std::forward_list where erase() is named erase_after().
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template <typename T, typename Allocator>
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constexpr auto ConstCastIterator(
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std::forward_list<T, Allocator>& c,
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typename std::forward_list<T, Allocator>::const_iterator it) {
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// The erase_after(it, it) trick used below does not work for libstdc++ [1],
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// thus we need a different way.
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// TODO(crbug.com/972541): Remove this workaround once libstdc++ is fixed on all
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// platforms.
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//
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// [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90857
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#if defined(__GLIBCXX__)
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return c.insert_after(it, {});
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#else
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return c.erase_after(it, it);
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#endif
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}
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// Specialized O(1) const casting for random access iterators. This is
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// necessary, because erase() is either not available (e.g. array-like
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// containers), or has O(n) complexity (e.g. std::deque or std::vector).
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template <typename Container,
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typename ConstIter,
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std::enable_if_t<internal::IsRandomAccessIter<ConstIter>>* = nullptr>
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constexpr auto ConstCastIterator(Container& c, ConstIter it) {
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using std::begin;
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using std::cbegin;
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return begin(c) + (it - cbegin(c));
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}
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namespace internal {
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template <typename Map, typename Key, typename Value>
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std::pair<typename Map::iterator, bool> InsertOrAssignImpl(Map& map,
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Key&& key,
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Value&& value) {
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auto lower = map.lower_bound(key);
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if (lower != map.end() && !map.key_comp()(key, lower->first)) {
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// key already exists, perform assignment.
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lower->second = std::forward<Value>(value);
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return {lower, false};
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}
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// key did not yet exist, insert it.
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return {map.emplace_hint(lower, std::forward<Key>(key),
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std::forward<Value>(value)),
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true};
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}
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template <typename Map, typename Key, typename Value>
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typename Map::iterator InsertOrAssignImpl(Map& map,
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typename Map::const_iterator hint,
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Key&& key,
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Value&& value) {
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auto&& key_comp = map.key_comp();
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if ((hint == map.begin() || key_comp(std::prev(hint)->first, key))) {
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if (hint == map.end() || key_comp(key, hint->first)) {
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// *(hint - 1) < key < *hint => key did not exist and hint is correct.
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return map.emplace_hint(hint, std::forward<Key>(key),
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std::forward<Value>(value));
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}
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if (!key_comp(hint->first, key)) {
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// key == *hint => key already exists and hint is correct.
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auto mutable_hint = ConstCastIterator(map, hint);
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mutable_hint->second = std::forward<Value>(value);
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return mutable_hint;
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}
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}
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// hint was not helpful, dispatch to hintless version.
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return InsertOrAssignImpl(map, std::forward<Key>(key),
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std::forward<Value>(value))
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.first;
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}
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template <typename Map, typename Key, typename... Args>
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std::pair<typename Map::iterator, bool> TryEmplaceImpl(Map& map,
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Key&& key,
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Args&&... args) {
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auto lower = map.lower_bound(key);
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if (lower != map.end() && !map.key_comp()(key, lower->first)) {
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// key already exists, do nothing.
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return {lower, false};
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}
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// key did not yet exist, insert it.
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return {map.emplace_hint(lower, std::piecewise_construct,
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std::forward_as_tuple(std::forward<Key>(key)),
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std::forward_as_tuple(std::forward<Args>(args)...)),
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true};
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}
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template <typename Map, typename Key, typename... Args>
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typename Map::iterator TryEmplaceImpl(Map& map,
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typename Map::const_iterator hint,
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Key&& key,
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Args&&... args) {
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auto&& key_comp = map.key_comp();
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if ((hint == map.begin() || key_comp(std::prev(hint)->first, key))) {
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if (hint == map.end() || key_comp(key, hint->first)) {
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// *(hint - 1) < key < *hint => key did not exist and hint is correct.
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return map.emplace_hint(
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hint, std::piecewise_construct,
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std::forward_as_tuple(std::forward<Key>(key)),
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std::forward_as_tuple(std::forward<Args>(args)...));
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}
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if (!key_comp(hint->first, key)) {
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// key == *hint => no-op, return correct hint.
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return ConstCastIterator(map, hint);
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}
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}
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// hint was not helpful, dispatch to hintless version.
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return TryEmplaceImpl(map, std::forward<Key>(key),
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std::forward<Args>(args)...)
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.first;
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}
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} // namespace internal
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// Implementation of C++17's std::map::insert_or_assign as a free function.
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template <typename Map, typename Value>
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std::pair<typename Map::iterator, bool>
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InsertOrAssign(Map& map, const typename Map::key_type& key, Value&& value) {
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return internal::InsertOrAssignImpl(map, key, std::forward<Value>(value));
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}
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template <typename Map, typename Value>
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std::pair<typename Map::iterator, bool>
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InsertOrAssign(Map& map, typename Map::key_type&& key, Value&& value) {
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return internal::InsertOrAssignImpl(map, std::move(key),
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std::forward<Value>(value));
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}
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// Implementation of C++17's std::map::insert_or_assign with hint as a free
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// function.
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template <typename Map, typename Value>
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typename Map::iterator InsertOrAssign(Map& map,
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typename Map::const_iterator hint,
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const typename Map::key_type& key,
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Value&& value) {
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return internal::InsertOrAssignImpl(map, hint, key,
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std::forward<Value>(value));
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}
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template <typename Map, typename Value>
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typename Map::iterator InsertOrAssign(Map& map,
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typename Map::const_iterator hint,
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typename Map::key_type&& key,
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Value&& value) {
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return internal::InsertOrAssignImpl(map, hint, std::move(key),
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std::forward<Value>(value));
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}
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// Implementation of C++17's std::map::try_emplace as a free function.
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template <typename Map, typename... Args>
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std::pair<typename Map::iterator, bool>
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TryEmplace(Map& map, const typename Map::key_type& key, Args&&... args) {
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return internal::TryEmplaceImpl(map, key, std::forward<Args>(args)...);
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}
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template <typename Map, typename... Args>
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std::pair<typename Map::iterator, bool> TryEmplace(Map& map,
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typename Map::key_type&& key,
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Args&&... args) {
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return internal::TryEmplaceImpl(map, std::move(key),
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std::forward<Args>(args)...);
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}
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// Implementation of C++17's std::map::try_emplace with hint as a free
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// function.
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template <typename Map, typename... Args>
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typename Map::iterator TryEmplace(Map& map,
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typename Map::const_iterator hint,
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const typename Map::key_type& key,
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Args&&... args) {
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return internal::TryEmplaceImpl(map, hint, key, std::forward<Args>(args)...);
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}
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template <typename Map, typename... Args>
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typename Map::iterator TryEmplace(Map& map,
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typename Map::const_iterator hint,
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typename Map::key_type&& key,
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Args&&... args) {
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return internal::TryEmplaceImpl(map, hint, std::move(key),
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std::forward<Args>(args)...);
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}
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// Returns true if the container is sorted.
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template <typename Container>
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bool STLIsSorted(const Container& cont) {
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return std::is_sorted(std::begin(cont), std::end(cont));
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}
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// Returns a new ResultType containing the difference of two sorted containers.
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template <typename ResultType, typename Arg1, typename Arg2>
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ResultType STLSetDifference(const Arg1& a1, const Arg2& a2) {
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DCHECK(STLIsSorted(a1));
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DCHECK(STLIsSorted(a2));
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ResultType difference;
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std::set_difference(a1.begin(), a1.end(),
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a2.begin(), a2.end(),
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std::inserter(difference, difference.end()));
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return difference;
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}
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// Returns a new ResultType containing the union of two sorted containers.
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template <typename ResultType, typename Arg1, typename Arg2>
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ResultType STLSetUnion(const Arg1& a1, const Arg2& a2) {
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DCHECK(STLIsSorted(a1));
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DCHECK(STLIsSorted(a2));
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ResultType result;
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std::set_union(a1.begin(), a1.end(),
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a2.begin(), a2.end(),
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std::inserter(result, result.end()));
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return result;
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}
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// Returns a new ResultType containing the intersection of two sorted
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// containers.
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template <typename ResultType, typename Arg1, typename Arg2>
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ResultType STLSetIntersection(const Arg1& a1, const Arg2& a2) {
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DCHECK(STLIsSorted(a1));
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DCHECK(STLIsSorted(a2));
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ResultType result;
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std::set_intersection(a1.begin(), a1.end(),
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a2.begin(), a2.end(),
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std::inserter(result, result.end()));
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return result;
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}
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// Returns true if the sorted container |a1| contains all elements of the sorted
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// container |a2|.
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template <typename Arg1, typename Arg2>
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bool STLIncludes(const Arg1& a1, const Arg2& a2) {
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DCHECK(STLIsSorted(a1));
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DCHECK(STLIsSorted(a2));
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return std::includes(a1.begin(), a1.end(),
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a2.begin(), a2.end());
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}
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// Erase/EraseIf are based on C++20's uniform container erasure API:
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// - https://eel.is/c++draft/libraryindex#:erase
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// - https://eel.is/c++draft/libraryindex#:erase_if
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// They provide a generic way to erase elements from a container.
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// The functions here implement these for the standard containers until those
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// functions are available in the C++ standard.
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// For Chromium containers overloads should be defined in their own headers
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// (like standard containers).
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// Note: there is no std::erase for standard associative containers so we don't
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// have it either.
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template <typename CharT, typename Traits, typename Allocator, typename Value>
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size_t Erase(std::basic_string<CharT, Traits, Allocator>& container,
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const Value& value) {
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auto it = std::remove(container.begin(), container.end(), value);
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size_t removed = std::distance(it, container.end());
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container.erase(it, container.end());
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return removed;
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}
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template <typename CharT, typename Traits, typename Allocator, class Predicate>
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size_t EraseIf(std::basic_string<CharT, Traits, Allocator>& container,
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Predicate pred) {
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auto it = std::remove_if(container.begin(), container.end(), pred);
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size_t removed = std::distance(it, container.end());
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container.erase(it, container.end());
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return removed;
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}
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template <class T, class Allocator, class Value>
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size_t Erase(std::deque<T, Allocator>& container, const Value& value) {
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auto it = std::remove(container.begin(), container.end(), value);
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size_t removed = std::distance(it, container.end());
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container.erase(it, container.end());
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return removed;
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}
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template <class T, class Allocator, class Predicate>
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size_t EraseIf(std::deque<T, Allocator>& container, Predicate pred) {
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auto it = std::remove_if(container.begin(), container.end(), pred);
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size_t removed = std::distance(it, container.end());
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container.erase(it, container.end());
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return removed;
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}
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template <class T, class Allocator, class Value>
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size_t Erase(std::vector<T, Allocator>& container, const Value& value) {
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auto it = std::remove(container.begin(), container.end(), value);
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size_t removed = std::distance(it, container.end());
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container.erase(it, container.end());
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return removed;
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}
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template <class T, class Allocator, class Predicate>
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size_t EraseIf(std::vector<T, Allocator>& container, Predicate pred) {
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auto it = std::remove_if(container.begin(), container.end(), pred);
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size_t removed = std::distance(it, container.end());
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container.erase(it, container.end());
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return removed;
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}
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template <class T, class Allocator, class Value>
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size_t Erase(std::forward_list<T, Allocator>& container, const Value& value) {
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// Unlike std::forward_list::remove, this function template accepts
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// heterogeneous types and does not force a conversion to the container's
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// value type before invoking the == operator.
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return EraseIf(container, [&](const T& cur) { return cur == value; });
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}
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template <class T, class Allocator, class Predicate>
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size_t EraseIf(std::forward_list<T, Allocator>& container, Predicate pred) {
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// Note: std::forward_list does not have a size() API, thus we need to use the
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// O(n) std::distance work-around. However, given that EraseIf is O(n)
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// already, this should not make a big difference.
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size_t old_size = std::distance(container.begin(), container.end());
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container.remove_if(pred);
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return old_size - std::distance(container.begin(), container.end());
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}
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template <class T, class Allocator, class Value>
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size_t Erase(std::list<T, Allocator>& container, const Value& value) {
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// Unlike std::list::remove, this function template accepts heterogeneous
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// types and does not force a conversion to the container's value type before
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// invoking the == operator.
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return EraseIf(container, [&](const T& cur) { return cur == value; });
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}
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template <class T, class Allocator, class Predicate>
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size_t EraseIf(std::list<T, Allocator>& container, Predicate pred) {
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size_t old_size = container.size();
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container.remove_if(pred);
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return old_size - container.size();
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}
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template <class Key, class T, class Compare, class Allocator, class Predicate>
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size_t EraseIf(std::map<Key, T, Compare, Allocator>& container,
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Predicate pred) {
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return internal::IterateAndEraseIf(container, pred);
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}
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template <class Key, class T, class Compare, class Allocator, class Predicate>
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size_t EraseIf(std::multimap<Key, T, Compare, Allocator>& container,
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Predicate pred) {
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return internal::IterateAndEraseIf(container, pred);
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}
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template <class Key, class Compare, class Allocator, class Predicate>
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size_t EraseIf(std::set<Key, Compare, Allocator>& container, Predicate pred) {
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return internal::IterateAndEraseIf(container, pred);
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}
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template <class Key, class Compare, class Allocator, class Predicate>
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size_t EraseIf(std::multiset<Key, Compare, Allocator>& container,
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Predicate pred) {
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return internal::IterateAndEraseIf(container, pred);
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}
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template <class Key,
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class T,
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class Hash,
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class KeyEqual,
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class Allocator,
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class Predicate>
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size_t EraseIf(std::unordered_map<Key, T, Hash, KeyEqual, Allocator>& container,
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Predicate pred) {
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return internal::IterateAndEraseIf(container, pred);
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}
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template <class Key,
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class T,
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class Hash,
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class KeyEqual,
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class Allocator,
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class Predicate>
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size_t EraseIf(
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std::unordered_multimap<Key, T, Hash, KeyEqual, Allocator>& container,
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Predicate pred) {
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return internal::IterateAndEraseIf(container, pred);
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}
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template <class Key,
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class Hash,
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class KeyEqual,
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class Allocator,
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class Predicate>
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size_t EraseIf(std::unordered_set<Key, Hash, KeyEqual, Allocator>& container,
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Predicate pred) {
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return internal::IterateAndEraseIf(container, pred);
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}
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template <class Key,
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class Hash,
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class KeyEqual,
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class Allocator,
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class Predicate>
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size_t EraseIf(
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std::unordered_multiset<Key, Hash, KeyEqual, Allocator>& container,
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Predicate pred) {
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return internal::IterateAndEraseIf(container, pred);
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}
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// A helper class to be used as the predicate with |EraseIf| to implement
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// in-place set intersection. Helps implement the algorithm of going through
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// each container an element at a time, erasing elements from the first
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// container if they aren't in the second container. Requires each container be
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// sorted. Note that the logic below appears inverted since it is returning
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// whether an element should be erased.
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template <class Collection>
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class IsNotIn {
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public:
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explicit IsNotIn(const Collection& collection)
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: i_(collection.begin()), end_(collection.end()) {}
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bool operator()(const typename Collection::value_type& x) {
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while (i_ != end_ && *i_ < x)
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++i_;
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if (i_ == end_)
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return true;
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if (*i_ == x) {
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++i_;
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return false;
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}
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return true;
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}
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private:
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typename Collection::const_iterator i_;
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const typename Collection::const_iterator end_;
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};
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// Helper for returning the optional value's address, or nullptr.
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template <class T>
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T* OptionalOrNullptr(base::Optional<T>& optional) {
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return optional.has_value() ? &optional.value() : nullptr;
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}
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template <class T>
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const T* OptionalOrNullptr(const base::Optional<T>& optional) {
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return optional.has_value() ? &optional.value() : nullptr;
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}
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} // namespace base
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#endif // BASE_STL_UTIL_H_
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