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// Copyright 2018 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.
#ifndef BASE_TASK_COMMON_INTRUSIVE_HEAP_H_
#define BASE_TASK_COMMON_INTRUSIVE_HEAP_H_
#include "base/containers/intrusive_heap.h"
namespace base {
namespace internal {
using HeapHandle = base::HeapHandle;
template <typename T>
struct IntrusiveHeapImpl {
struct GreaterUsingLessEqual {
bool operator()(const T& t1, const T& t2) const { return t2 <= t1; }
};
using type = base::IntrusiveHeap<T, GreaterUsingLessEqual>;
};
// base/task wants a min-heap that uses the <= operator, whereas
// base::IntrusiveHeap is a max-heap by default. This is a very thin adapter
// over that class that exposes minimal functionality required by the
// base/task IntrusiveHeap clients.
template <typename T>
class IntrusiveHeap : private IntrusiveHeapImpl<T>::type {
public:
using IntrusiveHeapImplType = typename IntrusiveHeapImpl<T>::type;
// The majority of sets in the scheduler have 0-3 items in them (a few will
// have perhaps up to 100), so this means we usually only have to allocate
// memory once.
static constexpr size_t kMinimumHeapSize = 4;
IntrusiveHeap() { IntrusiveHeapImplType::reserve(kMinimumHeapSize); }
~IntrusiveHeap() = default;
IntrusiveHeap& operator=(IntrusiveHeap&& other) = default;
bool empty() const { return IntrusiveHeapImplType::empty(); }
size_t size() const { return IntrusiveHeapImplType::size(); }
void Clear() {
IntrusiveHeapImplType::clear();
IntrusiveHeapImplType::reserve(kMinimumHeapSize);
}
const T& Min() const { return IntrusiveHeapImplType::top(); }
void Pop() { IntrusiveHeapImplType::pop(); }
void insert(T&& element) {
IntrusiveHeapImplType::insert(std::move(element));
}
void erase(HeapHandle handle) { IntrusiveHeapImplType::erase(handle); }
void ReplaceMin(T&& element) {
IntrusiveHeapImplType::ReplaceTop(std::move(element));
}
void ChangeKey(HeapHandle handle, T&& element) {
IntrusiveHeapImplType::Replace(handle, std::move(element));
}
const T& at(HeapHandle handle) const {
return IntrusiveHeapImplType::at(handle);
}
// Caution, mutating the heap invalidates iterators!
const T* begin() const { return IntrusiveHeapImplType::data(); }
const T* end() const { return IntrusiveHeapImplType::data() + size(); }
};
} // namespace internal
} // namespace base
#endif // BASE_TASK_COMMON_INTRUSIVE_HEAP_H_
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