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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 <unordered_map>
#include <unordered_set>
#include <vector>
#include "base/logging.h"
#include "base/optional.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;
}
}
} // namespace internal
// C++14 implementation of C++17's std::size():
// http://en.cppreference.com/w/cpp/iterator/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 (&)[N]) noexcept {
return N;
}
// C++14 implementation of C++17's std::empty():
// http://en.cppreference.com/w/cpp/iterator/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 (&)[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():
// http://en.cppreference.com/w/cpp/iterator/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].
//
// [1] http://en.cppreference.com/w/cpp/string/basic_string/data
// [2] http://en.cppreference.com/w/cpp/string/basic_string/operator_at
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();
}
// 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);
}
// Test to see if a set or map contains a particular key.
// Returns true if the key is in the collection.
template <typename Collection, typename Key>
bool ContainsKey(const Collection& collection, const Key& key) {
return collection.find(key) != collection.end();
}
namespace internal {
template <typename Collection>
class HasKeyType {
template <typename C>
static std::true_type test(typename C::key_type*);
template <typename C>
static std::false_type test(...);
public:
static constexpr bool value = decltype(test<Collection>(nullptr))::value;
};
} // namespace internal
// Test to see if a collection like a vector contains a particular value.
// Returns true if the value is in the collection.
// Don't use this on collections such as sets or maps. This is enforced by
// disabling this method if the collection defines a key_type.
template <typename Collection,
typename Value,
typename std::enable_if<!internal::HasKeyType<Collection>::value,
int>::type = 0>
bool ContainsValue(const Collection& collection, const Value& value) {
return std::find(std::begin(collection), std::end(collection), value) !=
std::end(collection);
}
// 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
// http://en.cppreference.com/w/cpp/experimental/lib_extensions_2
// 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_