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103 lines
3.3 KiB
C++
103 lines
3.3 KiB
C++
// Copyright 2011 The Chromium Authors
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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 <iterator>
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#include "base/check.h"
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namespace base {
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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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// 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(std::ranges::is_sorted(a1));
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DCHECK(std::ranges::is_sorted(a2));
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ResultType difference;
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std::set_difference(a1.begin(), a1.end(), 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(std::ranges::is_sorted(a1));
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DCHECK(std::ranges::is_sorted(a2));
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ResultType result;
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std::set_union(a1.begin(), a1.end(), 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(std::ranges::is_sorted(a1));
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DCHECK(std::ranges::is_sorted(a2));
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ResultType result;
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std::set_intersection(a1.begin(), a1.end(), 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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// 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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: it_(collection.begin()), end_(collection.end()) {}
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bool operator()(const typename Collection::value_type& x) {
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while (it_ != end_ && *it_ < x) {
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++it_;
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}
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if (it_ == end_ || *it_ != x) {
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return true;
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}
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++it_;
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return false;
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}
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private:
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typename Collection::const_iterator it_;
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const typename Collection::const_iterator end_;
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};
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} // namespace base
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#endif // BASE_STL_UTIL_H_
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