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//===-- list.h --------------------------------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef SCUDO_LIST_H_
#define SCUDO_LIST_H_
#include "internal_defs.h"
namespace scudo {
// Intrusive POD singly and doubly linked list.
// An object with all zero fields should represent a valid empty list. clear()
// should be called on all non-zero-initialized objects before using.
template <class T> class IteratorBase {
public:
explicit IteratorBase(T *CurrentT) : Current(CurrentT) {}
IteratorBase &operator++() {
Current = Current->Next;
return *this;
}
bool operator!=(IteratorBase Other) const { return Current != Other.Current; }
T &operator*() { return *Current; }
private:
T *Current;
};
template <class T> struct IntrusiveList {
bool empty() const { return Size == 0; }
uptr size() const { return Size; }
T *front() { return First; }
const T *front() const { return First; }
T *back() { return Last; }
const T *back() const { return Last; }
void clear() {
First = Last = nullptr;
Size = 0;
}
typedef IteratorBase<T> Iterator;
typedef IteratorBase<const T> ConstIterator;
Iterator begin() { return Iterator(First); }
Iterator end() { return Iterator(nullptr); }
ConstIterator begin() const { return ConstIterator(First); }
ConstIterator end() const { return ConstIterator(nullptr); }
void checkConsistency() const;
protected:
uptr Size = 0;
T *First = nullptr;
T *Last = nullptr;
};
template <class T> void IntrusiveList<T>::checkConsistency() const {
if (Size == 0) {
CHECK_EQ(First, nullptr);
CHECK_EQ(Last, nullptr);
} else {
uptr Count = 0;
for (T *I = First;; I = I->Next) {
Count++;
if (I == Last)
break;
}
CHECK_EQ(this->size(), Count);
CHECK_EQ(Last->Next, nullptr);
}
}
template <class T> struct SinglyLinkedList : public IntrusiveList<T> {
using IntrusiveList<T>::First;
using IntrusiveList<T>::Last;
using IntrusiveList<T>::Size;
using IntrusiveList<T>::empty;
void push_back(T *X) {
X->Next = nullptr;
if (empty())
First = X;
else
Last->Next = X;
Last = X;
Size++;
}
void push_front(T *X) {
if (empty())
Last = X;
X->Next = First;
First = X;
Size++;
}
void pop_front() {
DCHECK(!empty());
First = First->Next;
if (!First)
Last = nullptr;
Size--;
}
// Insert X next to Prev
void insert(T *Prev, T *X) {
DCHECK(!empty());
DCHECK_NE(Prev, nullptr);
DCHECK_NE(X, nullptr);
X->Next = Prev->Next;
Prev->Next = X;
if (Last == Prev)
Last = X;
++Size;
}
void extract(T *Prev, T *X) {
DCHECK(!empty());
DCHECK_NE(Prev, nullptr);
DCHECK_NE(X, nullptr);
DCHECK_EQ(Prev->Next, X);
Prev->Next = X->Next;
if (Last == X)
Last = Prev;
Size--;
}
void append_back(SinglyLinkedList<T> *L) {
DCHECK_NE(this, L);
if (L->empty())
return;
if (empty()) {
*this = *L;
} else {
Last->Next = L->First;
Last = L->Last;
Size += L->size();
}
L->clear();
}
};
template <class T> struct DoublyLinkedList : IntrusiveList<T> {
using IntrusiveList<T>::First;
using IntrusiveList<T>::Last;
using IntrusiveList<T>::Size;
using IntrusiveList<T>::empty;
void push_front(T *X) {
X->Prev = nullptr;
if (empty()) {
Last = X;
} else {
DCHECK_EQ(First->Prev, nullptr);
First->Prev = X;
}
X->Next = First;
First = X;
Size++;
}
// Inserts X before Y.
void insert(T *X, T *Y) {
if (Y == First)
return push_front(X);
T *Prev = Y->Prev;
// This is a hard CHECK to ensure consistency in the event of an intentional
// corruption of Y->Prev, to prevent a potential write-{4,8}.
CHECK_EQ(Prev->Next, Y);
Prev->Next = X;
X->Prev = Prev;
X->Next = Y;
Y->Prev = X;
Size++;
}
void push_back(T *X) {
X->Next = nullptr;
if (empty()) {
First = X;
} else {
DCHECK_EQ(Last->Next, nullptr);
Last->Next = X;
}
X->Prev = Last;
Last = X;
Size++;
}
void pop_front() {
DCHECK(!empty());
First = First->Next;
if (!First)
Last = nullptr;
else
First->Prev = nullptr;
Size--;
}
// The consistency of the adjacent links is aggressively checked in order to
// catch potential corruption attempts, that could yield a mirrored
// write-{4,8} primitive. nullptr checks are deemed less vital.
void remove(T *X) {
T *Prev = X->Prev;
T *Next = X->Next;
if (Prev) {
CHECK_EQ(Prev->Next, X);
Prev->Next = Next;
}
if (Next) {
CHECK_EQ(Next->Prev, X);
Next->Prev = Prev;
}
if (First == X) {
DCHECK_EQ(Prev, nullptr);
First = Next;
} else {
DCHECK_NE(Prev, nullptr);
}
if (Last == X) {
DCHECK_EQ(Next, nullptr);
Last = Prev;
} else {
DCHECK_NE(Next, nullptr);
}
Size--;
}
};
} // namespace scudo
#endif // SCUDO_LIST_H_
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