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/*
* Copyright 2012 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef SkTDLinkedList_DEFINED
#define SkTDLinkedList_DEFINED
#include "SkTypes.h"
/**
* Helper class to automatically initialize the doubly linked list
* created pointers.
*/
template <typename T> class SkPtrWrapper {
public:
SkPtrWrapper() : fPtr(NULL) {}
SkPtrWrapper& operator =(T* ptr) { fPtr = ptr; return *this; }
operator T*() const { return fPtr; }
T* operator->() { return fPtr; }
private:
T* fPtr;
};
/**
* This macro creates the member variables required by
* the SkTDLinkedList class. It should be placed in the private section
* of any class that will be stored in a double linked list.
*/
#define SK_DEFINE_DLINKEDLIST_INTERFACE(ClassName) \
friend class SkTDLinkedList<ClassName>; \
/* back pointer to the owning list - for debugging */ \
SkDEBUGCODE(SkPtrWrapper<SkTDLinkedList<ClassName> > fList;)\
SkPtrWrapper<ClassName> fPrev; \
SkPtrWrapper<ClassName> fNext;
/**
* This class implements a templated internal doubly linked list data structure.
*/
template <class T> class SkTDLinkedList : public SkNoncopyable {
public:
SkTDLinkedList()
: fHead(NULL)
, fTail(NULL) {
}
void remove(T* entry) {
SkASSERT(NULL != fHead && NULL != fTail);
SkASSERT(this->isInList(entry));
T* prev = entry->fPrev;
T* next = entry->fNext;
if (NULL != prev) {
prev->fNext = next;
} else {
fHead = next;
}
if (NULL != next) {
next->fPrev = prev;
} else {
fTail = prev;
}
entry->fPrev = NULL;
entry->fNext = NULL;
#ifdef SK_DEBUG
entry->fList = NULL;
#endif
}
void addToHead(T* entry) {
SkASSERT(NULL == entry->fPrev && NULL == entry->fNext);
SkASSERT(NULL == entry->fList);
entry->fPrev = NULL;
entry->fNext = fHead;
if (NULL != fHead) {
fHead->fPrev = entry;
}
fHead = entry;
if (NULL == fTail) {
fTail = entry;
}
#ifdef SK_DEBUG
entry->fList = this;
#endif
}
bool isEmpty() const {
return NULL == fHead && NULL == fTail;
}
T* head() { return fHead; }
T* tail() { return fTail; }
class Iter {
public:
enum IterStart {
kHead_IterStart,
kTail_IterStart
};
Iter() : fCur(NULL) {}
T* init(SkTDLinkedList& list, IterStart startLoc) {
if (kHead_IterStart == startLoc) {
fCur = list.fHead;
} else {
SkASSERT(kTail_IterStart == startLoc);
fCur = list.fTail;
}
return fCur;
}
/**
* Return the next/previous element in the list or NULL if at the end.
*/
T* next() {
if (NULL == fCur) {
return NULL;
}
fCur = fCur->fNext;
return fCur;
}
T* prev() {
if (NULL == fCur) {
return NULL;
}
fCur = fCur->fPrev;
return fCur;
}
private:
T* fCur;
};
#ifdef SK_DEBUG
void validate() const {
GrAssert(!fHead == !fTail);
}
/**
* Debugging-only method that uses the list back pointer to check if
* 'entry' is indeed in 'this' list.
*/
bool isInList(const T* entry) const {
return entry->fList == this;
}
/**
* Debugging-only method that laboriously counts the list entries.
*/
int countEntries() const {
int count = 0;
for (T* entry = fHead; NULL != entry; entry = entry->fNext) {
++count;
}
return count;
}
#endif // SK_DEBUG
private:
T* fHead;
T* fTail;
typedef SkNoncopyable INHERITED;
};
#endif // SkTDLinkedList_DEFINED
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