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// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// Derived from google3/util/gtl/stl_util.h
#ifndef BASE_STL_UTIL_H_
#define BASE_STL_UTIL_H_
#include <algorithm>
#include <deque>
#include <forward_list>
#include <functional>
#include <initializer_list>
#include <iterator>
#include <list>
#include <map>
#include <set>
#include <string>
#include <type_traits>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
#include "base/logging.h"
#include "base/optional.h"
#include "base/template_util.h"
namespace base {
namespace internal {
// Calls erase on iterators of matching elements.
template <typename Container, typename Predicate>
void IterateAndEraseIf(Container& container, Predicate pred) {
for (auto it = container.begin(); it != container.end();) {
if (pred(*it))
it = container.erase(it);
else
++it;
}
}
template <typename Iter>
constexpr bool IsRandomAccessIter =
std::is_same<typename std::iterator_traits<Iter>::iterator_category,
std::random_access_iterator_tag>::value;
// Utility type traits used for specializing base::Contains() below.
template <typename Container, typename Element, typename = void>
struct HasFindWithNpos : std::false_type {};
template <typename Container, typename Element>
struct HasFindWithNpos<
Container,
Element,
void_t<decltype(std::declval<const Container&>().find(
std::declval<const Element&>()) != Container::npos)>>
: std::true_type {};
template <typename Container, typename Element, typename = void>
struct HasFindWithEnd : std::false_type {};
template <typename Container, typename Element>
struct HasFindWithEnd<Container,
Element,
void_t<decltype(std::declval<const Container&>().find(
std::declval<const Element&>()) !=
std::declval<const Container&>().end())>>
: std::true_type {};
template <typename Container, typename Element, typename = void>
struct HasContains : std::false_type {};
template <typename Container, typename Element>
struct HasContains<Container,
Element,
void_t<decltype(std::declval<const Container&>().contains(
std::declval<const Element&>()))>> : std::true_type {};
} // namespace internal
// C++14 implementation of C++17's std::size():
template <typename Container>
constexpr auto size(const Container& c) -> decltype(c.size()) {
return c.size();
}
template <typename T, size_t N>
constexpr size_t size(const T (&array)[N]) noexcept {
return N;
}
// C++14 implementation of C++17's std::empty():
template <typename Container>
constexpr auto empty(const Container& c) -> decltype(c.empty()) {
return c.empty();
}
template <typename T, size_t N>
constexpr bool empty(const T (&array)[N]) noexcept {
return false;
}
template <typename T>
constexpr bool empty(std::initializer_list<T> il) noexcept {
return il.size() == 0;
}
// C++14 implementation of C++17's std::data():
template <typename Container>
constexpr auto data(Container& c) -> decltype(c.data()) {
return c.data();
}
// std::basic_string::data() had no mutable overload prior to C++17 [1].
// Hence this overload is provided.
// Note: str[0] is safe even for empty strings, as they are guaranteed to be
// null-terminated [2].
//
template <typename CharT, typename Traits, typename Allocator>
CharT* data(std::basic_string<CharT, Traits, Allocator>& str) {
return std::addressof(str[0]);
}
template <typename Container>
constexpr auto data(const Container& c) -> decltype(c.data()) {
return c.data();
}
template <typename T, size_t N>
constexpr T* data(T (&array)[N]) noexcept {
return array;
}
template <typename T>
constexpr const T* data(std::initializer_list<T> il) noexcept {
return il.begin();
}
// std::array::data() was not constexpr prior to C++17 [1].
// Hence these overloads are provided.
//
template <typename T, size_t N>
constexpr T* data(std::array<T, N>& array) noexcept {
return !array.empty() ? &array[0] : nullptr;
}
template <typename T, size_t N>
constexpr const T* data(const std::array<T, N>& array) noexcept {
return !array.empty() ? &array[0] : nullptr;
}
// C++14 implementation of C++17's std::as_const():
template <typename T>
constexpr std::add_const_t<T>& as_const(T& t) noexcept {
return t;
}
template <typename T>
void as_const(const T&& t) = delete;
// Returns a const reference to the underlying container of a container adapter.
// Works for std::priority_queue, std::queue, and std::stack.
template <class A>
const typename A::container_type& GetUnderlyingContainer(const A& adapter) {
struct ExposedAdapter : A {
using A::c;
};
return adapter.*&ExposedAdapter::c;
}
// Clears internal memory of an STL object.
// STL clear()/reserve(0) does not always free internal memory allocated
// This function uses swap/destructor to ensure the internal memory is freed.
template<class T>
void STLClearObject(T* obj) {
T tmp;
tmp.swap(*obj);
// Sometimes "T tmp" allocates objects with memory (arena implementation?).
// Hence using additional reserve(0) even if it doesn't always work.
obj->reserve(0);
}
// Counts the number of instances of val in a container.
template <typename Container, typename T>
typename std::iterator_traits<
typename Container::const_iterator>::difference_type
STLCount(const Container& container, const T& val) {
return std::count(container.begin(), container.end(), val);
}
// General purpose implementation to check if |container| contains |value|.
template <typename Container,
typename Value,
std::enable_if_t<
!internal::HasFindWithNpos<Container, Value>::value &&
!internal::HasFindWithEnd<Container, Value>::value &&
!internal::HasContains<Container, Value>::value>* = nullptr>
bool Contains(const Container& container, const Value& value) {
using std::begin;
using std::end;
return std::find(begin(container), end(container), value) != end(container);
}
// Specialized Contains() implementation for when |container| has a find()
// member function and a static npos member, but no contains() member function.
template <typename Container,
typename Value,
std::enable_if_t<internal::HasFindWithNpos<Container, Value>::value &&
!internal::HasContains<Container, Value>::value>* =
nullptr>
bool Contains(const Container& container, const Value& value) {
return container.find(value) != Container::npos;
}
// Specialized Contains() implementation for when |container| has a find()
// and end() member function, but no contains() member function.
template <typename Container,
typename Value,
std::enable_if_t<internal::HasFindWithEnd<Container, Value>::value &&
!internal::HasContains<Container, Value>::value>* =
nullptr>
bool Contains(const Container& container, const Value& value) {
return container.find(value) != container.end();
}
// Specialized Contains() implementation for when |container| has a contains()
// member function.
template <
typename Container,
typename Value,
std::enable_if_t<internal::HasContains<Container, Value>::value>* = nullptr>
bool Contains(const Container& container, const Value& value) {
return container.contains(value);
}
// O(1) implementation of const casting an iterator for any sequence,
// associative or unordered associative container in the STL.
//
template <typename Container,
typename ConstIter,
std::enable_if_t<!internal::IsRandomAccessIter<ConstIter>>* = nullptr>
constexpr auto ConstCastIterator(Container& c, ConstIter it) {
return c.erase(it, it);
}
// Explicit overload for std::forward_list where erase() is named erase_after().
template <typename T, typename Allocator>
constexpr auto ConstCastIterator(
std::forward_list<T, Allocator>& c,
typename std::forward_list<T, Allocator>::const_iterator it) {
// The erase_after(it, it) trick used below does not work for libstdc++ [1],
// thus we need a different way.
// TODO(crbug.com/972541): Remove this workaround once libstdc++ is fixed on all
// platforms.
//
#if defined(__GLIBCXX__)
return c.insert_after(it, {});
#else
return c.erase_after(it, it);
#endif
}
// Specialized O(1) const casting for random access iterators. This is
// necessary, because erase() is either not available (e.g. array-like
// containers), or has O(n) complexity (e.g. std::deque or std::vector).
template <typename Container,
typename ConstIter,
std::enable_if_t<internal::IsRandomAccessIter<ConstIter>>* = nullptr>
constexpr auto ConstCastIterator(Container& c, ConstIter it) {
using std::begin;
using std::cbegin;
return begin(c) + (it - cbegin(c));
}
namespace internal {
template <typename Map, typename Key, typename Value>
std::pair<typename Map::iterator, bool> InsertOrAssignImpl(Map& map,
Key&& key,
Value&& value) {
auto lower = map.lower_bound(key);
if (lower != map.end() && !map.key_comp()(key, lower->first)) {
// key already exists, perform assignment.
lower->second = std::forward<Value>(value);
return {lower, false};
}
// key did not yet exist, insert it.
return {map.emplace_hint(lower, std::forward<Key>(key),
std::forward<Value>(value)),
true};
}
template <typename Map, typename Key, typename Value>
typename Map::iterator InsertOrAssignImpl(Map& map,
typename Map::const_iterator hint,
Key&& key,
Value&& value) {
auto&& key_comp = map.key_comp();
if ((hint == map.begin() || key_comp(std::prev(hint)->first, key))) {
if (hint == map.end() || key_comp(key, hint->first)) {
// *(hint - 1) < key < *hint => key did not exist and hint is correct.
return map.emplace_hint(hint, std::forward<Key>(key),
std::forward<Value>(value));
}
if (!key_comp(hint->first, key)) {
// key == *hint => key already exists and hint is correct.
auto mutable_hint = ConstCastIterator(map, hint);
mutable_hint->second = std::forward<Value>(value);
return mutable_hint;
}
}
// hint was not helpful, dispatch to hintless version.
return InsertOrAssignImpl(map, std::forward<Key>(key),
std::forward<Value>(value))
.first;
}
template <typename Map, typename Key, typename... Args>
std::pair<typename Map::iterator, bool> TryEmplaceImpl(Map& map,
Key&& key,
Args&&... args) {
auto lower = map.lower_bound(key);
if (lower != map.end() && !map.key_comp()(key, lower->first)) {
// key already exists, do nothing.
return {lower, false};
}
// key did not yet exist, insert it.
return {map.emplace_hint(lower, std::piecewise_construct,
std::forward_as_tuple(std::forward<Key>(key)),
std::forward_as_tuple(std::forward<Args>(args)...)),
true};
}
template <typename Map, typename Key, typename... Args>
typename Map::iterator TryEmplaceImpl(Map& map,
typename Map::const_iterator hint,
Key&& key,
Args&&... args) {
auto&& key_comp = map.key_comp();
if ((hint == map.begin() || key_comp(std::prev(hint)->first, key))) {
if (hint == map.end() || key_comp(key, hint->first)) {
// *(hint - 1) < key < *hint => key did not exist and hint is correct.
return map.emplace_hint(
hint, std::piecewise_construct,
std::forward_as_tuple(std::forward<Key>(key)),
std::forward_as_tuple(std::forward<Args>(args)...));
}
if (!key_comp(hint->first, key)) {
// key == *hint => no-op, return correct hint.
return ConstCastIterator(map, hint);
}
}
// hint was not helpful, dispatch to hintless version.
return TryEmplaceImpl(map, std::forward<Key>(key),
std::forward<Args>(args)...)
.first;
}
} // namespace internal
// Implementation of C++17's std::map::insert_or_assign as a free function.
template <typename Map, typename Value>
std::pair<typename Map::iterator, bool>
InsertOrAssign(Map& map, const typename Map::key_type& key, Value&& value) {
return internal::InsertOrAssignImpl(map, key, std::forward<Value>(value));
}
template <typename Map, typename Value>
std::pair<typename Map::iterator, bool>
InsertOrAssign(Map& map, typename Map::key_type&& key, Value&& value) {
return internal::InsertOrAssignImpl(map, std::move(key),
std::forward<Value>(value));
}
// Implementation of C++17's std::map::insert_or_assign with hint as a free
// function.
template <typename Map, typename Value>
typename Map::iterator InsertOrAssign(Map& map,
typename Map::const_iterator hint,
const typename Map::key_type& key,
Value&& value) {
return internal::InsertOrAssignImpl(map, hint, key,
std::forward<Value>(value));
}
template <typename Map, typename Value>
typename Map::iterator InsertOrAssign(Map& map,
typename Map::const_iterator hint,
typename Map::key_type&& key,
Value&& value) {
return internal::InsertOrAssignImpl(map, hint, std::move(key),
std::forward<Value>(value));
}
// Implementation of C++17's std::map::try_emplace as a free function.
template <typename Map, typename... Args>
std::pair<typename Map::iterator, bool>
TryEmplace(Map& map, const typename Map::key_type& key, Args&&... args) {
return internal::TryEmplaceImpl(map, key, std::forward<Args>(args)...);
}
template <typename Map, typename... Args>
std::pair<typename Map::iterator, bool> TryEmplace(Map& map,
typename Map::key_type&& key,
Args&&... args) {
return internal::TryEmplaceImpl(map, std::move(key),
std::forward<Args>(args)...);
}
// Implementation of C++17's std::map::try_emplace with hint as a free
// function.
template <typename Map, typename... Args>
typename Map::iterator TryEmplace(Map& map,
typename Map::const_iterator hint,
const typename Map::key_type& key,
Args&&... args) {
return internal::TryEmplaceImpl(map, hint, key, std::forward<Args>(args)...);
}
template <typename Map, typename... Args>
typename Map::iterator TryEmplace(Map& map,
typename Map::const_iterator hint,
typename Map::key_type&& key,
Args&&... args) {
return internal::TryEmplaceImpl(map, hint, std::move(key),
std::forward<Args>(args)...);
}
// Returns true if the container is sorted.
template <typename Container>
bool STLIsSorted(const Container& cont) {
return std::is_sorted(std::begin(cont), std::end(cont));
}
// Returns a new ResultType containing the difference of two sorted containers.
template <typename ResultType, typename Arg1, typename Arg2>
ResultType STLSetDifference(const Arg1& a1, const Arg2& a2) {
DCHECK(STLIsSorted(a1));
DCHECK(STLIsSorted(a2));
ResultType difference;
std::set_difference(a1.begin(), a1.end(),
a2.begin(), a2.end(),
std::inserter(difference, difference.end()));
return difference;
}
// Returns a new ResultType containing the union of two sorted containers.
template <typename ResultType, typename Arg1, typename Arg2>
ResultType STLSetUnion(const Arg1& a1, const Arg2& a2) {
DCHECK(STLIsSorted(a1));
DCHECK(STLIsSorted(a2));
ResultType result;
std::set_union(a1.begin(), a1.end(),
a2.begin(), a2.end(),
std::inserter(result, result.end()));
return result;
}
// Returns a new ResultType containing the intersection of two sorted
// containers.
template <typename ResultType, typename Arg1, typename Arg2>
ResultType STLSetIntersection(const Arg1& a1, const Arg2& a2) {
DCHECK(STLIsSorted(a1));
DCHECK(STLIsSorted(a2));
ResultType result;
std::set_intersection(a1.begin(), a1.end(),
a2.begin(), a2.end(),
std::inserter(result, result.end()));
return result;
}
// Returns true if the sorted container |a1| contains all elements of the sorted
// container |a2|.
template <typename Arg1, typename Arg2>
bool STLIncludes(const Arg1& a1, const Arg2& a2) {
DCHECK(STLIsSorted(a1));
DCHECK(STLIsSorted(a2));
return std::includes(a1.begin(), a1.end(),
a2.begin(), a2.end());
}
// Erase/EraseIf are based on library fundamentals ts v2 erase/erase_if
// They provide a generic way to erase elements from a container.
// The functions here implement these for the standard containers until those
// functions are available in the C++ standard.
// For Chromium containers overloads should be defined in their own headers
// (like standard containers).
// Note: there is no std::erase for standard associative containers so we don't
// have it either.
template <typename CharT, typename Traits, typename Allocator, typename Value>
void Erase(std::basic_string<CharT, Traits, Allocator>& container,
const Value& value) {
container.erase(std::remove(container.begin(), container.end(), value),
container.end());
}
template <typename CharT, typename Traits, typename Allocator, class Predicate>
void EraseIf(std::basic_string<CharT, Traits, Allocator>& container,
Predicate pred) {
container.erase(std::remove_if(container.begin(), container.end(), pred),
container.end());
}
template <class T, class Allocator, class Value>
void Erase(std::deque<T, Allocator>& container, const Value& value) {
container.erase(std::remove(container.begin(), container.end(), value),
container.end());
}
template <class T, class Allocator, class Predicate>
void EraseIf(std::deque<T, Allocator>& container, Predicate pred) {
container.erase(std::remove_if(container.begin(), container.end(), pred),
container.end());
}
template <class T, class Allocator, class Value>
void Erase(std::vector<T, Allocator>& container, const Value& value) {
container.erase(std::remove(container.begin(), container.end(), value),
container.end());
}
template <class T, class Allocator, class Predicate>
void EraseIf(std::vector<T, Allocator>& container, Predicate pred) {
container.erase(std::remove_if(container.begin(), container.end(), pred),
container.end());
}
template <class T, class Allocator, class Value>
void Erase(std::forward_list<T, Allocator>& container, const Value& value) {
// Unlike std::forward_list::remove, this function template accepts
// heterogeneous types and does not force a conversion to the container's
// value type before invoking the == operator.
container.remove_if([&](const T& cur) { return cur == value; });
}
template <class T, class Allocator, class Predicate>
void EraseIf(std::forward_list<T, Allocator>& container, Predicate pred) {
container.remove_if(pred);
}
template <class T, class Allocator, class Value>
void Erase(std::list<T, Allocator>& container, const Value& value) {
// Unlike std::list::remove, this function template accepts heterogeneous
// types and does not force a conversion to the container's value type before
// invoking the == operator.
container.remove_if([&](const T& cur) { return cur == value; });
}
template <class T, class Allocator, class Predicate>
void EraseIf(std::list<T, Allocator>& container, Predicate pred) {
container.remove_if(pred);
}
template <class Key, class T, class Compare, class Allocator, class Predicate>
void EraseIf(std::map<Key, T, Compare, Allocator>& container, Predicate pred) {
internal::IterateAndEraseIf(container, pred);
}
template <class Key, class T, class Compare, class Allocator, class Predicate>
void EraseIf(std::multimap<Key, T, Compare, Allocator>& container,
Predicate pred) {
internal::IterateAndEraseIf(container, pred);
}
template <class Key, class Compare, class Allocator, class Predicate>
void EraseIf(std::set<Key, Compare, Allocator>& container, Predicate pred) {
internal::IterateAndEraseIf(container, pred);
}
template <class Key, class Compare, class Allocator, class Predicate>
void EraseIf(std::multiset<Key, Compare, Allocator>& container,
Predicate pred) {
internal::IterateAndEraseIf(container, pred);
}
template <class Key,
class T,
class Hash,
class KeyEqual,
class Allocator,
class Predicate>
void EraseIf(std::unordered_map<Key, T, Hash, KeyEqual, Allocator>& container,
Predicate pred) {
internal::IterateAndEraseIf(container, pred);
}
template <class Key,
class T,
class Hash,
class KeyEqual,
class Allocator,
class Predicate>
void EraseIf(
std::unordered_multimap<Key, T, Hash, KeyEqual, Allocator>& container,
Predicate pred) {
internal::IterateAndEraseIf(container, pred);
}
template <class Key,
class Hash,
class KeyEqual,
class Allocator,
class Predicate>
void EraseIf(std::unordered_set<Key, Hash, KeyEqual, Allocator>& container,
Predicate pred) {
internal::IterateAndEraseIf(container, pred);
}
template <class Key,
class Hash,
class KeyEqual,
class Allocator,
class Predicate>
void EraseIf(std::unordered_multiset<Key, Hash, KeyEqual, Allocator>& container,
Predicate pred) {
internal::IterateAndEraseIf(container, pred);
}
// A helper class to be used as the predicate with |EraseIf| to implement
// in-place set intersection. Helps implement the algorithm of going through
// each container an element at a time, erasing elements from the first
// container if they aren't in the second container. Requires each container be
// sorted. Note that the logic below appears inverted since it is returning
// whether an element should be erased.
template <class Collection>
class IsNotIn {
public:
explicit IsNotIn(const Collection& collection)
: i_(collection.begin()), end_(collection.end()) {}
bool operator()(const typename Collection::value_type& x) {
while (i_ != end_ && *i_ < x)
++i_;
if (i_ == end_)
return true;
if (*i_ == x) {
++i_;
return false;
}
return true;
}
private:
typename Collection::const_iterator i_;
const typename Collection::const_iterator end_;
};
// Helper for returning the optional value's address, or nullptr.
template <class T>
T* OptionalOrNullptr(base::Optional<T>& optional) {
return optional.has_value() ? &optional.value() : nullptr;
}
template <class T>
const T* OptionalOrNullptr(const base::Optional<T>& optional) {
return optional.has_value() ? &optional.value() : nullptr;
}
} // namespace base
#endif // BASE_STL_UTIL_H_