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/*
* Copyright 2016 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef SkSinglyLinkedList_DEFINED
#define SkSinglyLinkedList_DEFINED
#include <utility>
#include "SkMakeUnique.h"
#include "SkTypes.h"
template <typename T> class SkSinglyLinkedList {
struct Node;
public:
SkSinglyLinkedList() {}
~SkSinglyLinkedList() { this->reset(); }
void reset() {
SkASSERT(fHead != nullptr || nullptr == fTail);
// Use a while loop rather than recursion to avoid stack overflow.
std::unique_ptr<Node> node = std::move(fHead);
while (node) {
std::unique_ptr<Node> next = std::move(node->fNext);
SkASSERT(next || node.get() == fTail);
node = std::move(next);
}
fTail = nullptr;
}
T* back() { return fTail ? &fTail->fData : nullptr; }
T* front() { return fHead ? &fHead->fData : nullptr; }
bool empty() const { return fHead == nullptr; }
#ifdef SK_DEBUG
int count() { // O(n), debug only.
int count = 0;
for (Node* node = fHead.get(); node; node = node->fNext.get()) {
++count;
}
return count;
}
#endif
void pop_front() {
if (fHead) {
fHead = std::move(fHead->fNext);
if (!fHead) {
fTail = nullptr;
}
}
}
template <class... Args> T* emplace_front(Args&&... args) {
fHead = skstd::make_unique<Node>(std::move(fHead), std::forward<Args>(args)...);
if (!fTail) {
fTail = fHead.get();
}
return &fHead->fData;
}
template <class... Args> T* emplace_back(Args&&... args) {
std::unique_ptr<Node>* dst = fTail ? &fTail->fNext : &fHead;
*dst = skstd::make_unique<Node>(nullptr, std::forward<Args>(args)...);
fTail = dst->get();
return &fTail->fData;
}
class ConstIter {
public:
void operator++() { fNode = fNode->fNext.get(); }
const T& operator*() const { return fNode->fData; }
bool operator!=(const ConstIter& rhs) const { return fNode != rhs.fNode; }
ConstIter(const Node* n) : fNode(n) {}
private:
const Node* fNode;
};
ConstIter begin() const { return ConstIter(fHead.get()); }
ConstIter end() const { return ConstIter(nullptr); }
private:
struct Node {
T fData;
std::unique_ptr<Node> fNext;
template <class... Args>
Node(std::unique_ptr<Node> n, Args&&... args)
: fData(std::forward<Args>(args)...), fNext(std::move(n)) {}
};
std::unique_ptr<Node> fHead;
Node* fTail = nullptr;
SkSinglyLinkedList(const SkSinglyLinkedList<T>&) = delete;
SkSinglyLinkedList& operator=(const SkSinglyLinkedList<T>&) = delete;
};
#endif // SkSinglyLinkedList_DEFINED
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