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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 SkTLList_DEFINED
#define SkTLList_DEFINED
#include "SkTInternalLList.h"
#include "SkMalloc.h"
#include "SkTypes.h"
#include <utility>
/** Doubly-linked list of objects. The objects' lifetimes are controlled by the list. I.e. the
the list creates the objects and they are deleted upon removal. This class block-allocates
space for entries based on a param passed to the constructor.
Elements of the list can be constructed in place using the following macros:
SkNEW_INSERT_IN_LLIST_BEFORE(list, location, type_name, args)
SkNEW_INSERT_IN_LLIST_AFTER(list, location, type_name, args)
where list is a SkTLList<type_name>*, location is an iterator, and args is the paren-surrounded
constructor arguments for type_name. These macros behave like addBefore() and addAfter().
allocCnt is the number of objects to allocate as a group. In the worst case fragmentation
each object is using the space required for allocCnt unfragmented objects.
*/
template <typename T, unsigned int N> class SkTLList : SkNoncopyable {
private:
struct Block;
struct Node {
char fObj[sizeof(T)];
SK_DECLARE_INTERNAL_LLIST_INTERFACE(Node);
Block* fBlock; // owning block.
};
typedef SkTInternalLList<Node> NodeList;
public:
class Iter;
// Having fCount initialized to -1 indicates that the first time we attempt to grab a free node
// all the nodes in the pre-allocated first block need to be inserted into the free list. This
// allows us to skip that loop in instances when the list is never populated.
SkTLList() : fCount(-1) {}
~SkTLList() {
this->validate();
typename NodeList::Iter iter;
Node* node = iter.init(fList, Iter::kHead_IterStart);
while (node) {
SkTCast<T*>(node->fObj)->~T();
Block* block = node->fBlock;
node = iter.next();
if (0 == --block->fNodesInUse) {
for (unsigned int i = 0; i < N; ++i) {
block->fNodes[i].~Node();
}
if (block != &fFirstBlock) {
sk_free(block);
}
}
}
}
/** Adds a new element to the list at the head. */
template <typename... Args> T* addToHead(Args&&... args) {
this->validate();
Node* node = this->createNode();
fList.addToHead(node);
this->validate();
return new (node->fObj) T(std::forward<Args>(args)...);
}
/** Adds a new element to the list at the tail. */
template <typename... Args> T* addToTail(Args&&... args) {
this->validate();
Node* node = this->createNode();
fList.addToTail(node);
this->validate();
return new (node->fObj) T(std::forward<Args>(args)...);
}
/** Adds a new element to the list before the location indicated by the iterator. If the
iterator refers to a nullptr location then the new element is added at the tail */
template <typename... Args> T* addBefore(Iter location, Args&&... args) {
this->validate();
Node* node = this->createNode();
fList.addBefore(node, location.getNode());
this->validate();
return new (node->fObj) T(std::forward<Args>(args)...);
}
/** Adds a new element to the list after the location indicated by the iterator. If the
iterator refers to a nullptr location then the new element is added at the head */
template <typename... Args> T* addAfter(Iter location, Args&&... args) {
this->validate();
Node* node = this->createNode();
fList.addAfter(node, location.getNode());
this->validate();
return new (node->fObj) T(std::forward<Args>(args)...);
}
/** Convenience methods for getting an iterator initialized to the head/tail of the list. */
Iter headIter() const { return Iter(*this, Iter::kHead_IterStart); }
Iter tailIter() const { return Iter(*this, Iter::kTail_IterStart); }
T* head() { return Iter(*this, Iter::kHead_IterStart).get(); }
T* tail() { return Iter(*this, Iter::kTail_IterStart).get(); }
const T* head() const { return Iter(*this, Iter::kHead_IterStart).get(); }
const T* tail() const { return Iter(*this, Iter::kTail_IterStart).get(); }
void popHead() {
this->validate();
Node* node = fList.head();
if (node) {
this->removeNode(node);
}
this->validate();
}
void popTail() {
this->validate();
Node* node = fList.head();
if (node) {
this->removeNode(node);
}
this->validate();
}
void remove(T* t) {
this->validate();
Node* node = reinterpret_cast<Node*>(t);
SkASSERT(reinterpret_cast<T*>(node->fObj) == t);
this->removeNode(node);
this->validate();
}
void reset() {
this->validate();
Iter iter(*this, Iter::kHead_IterStart);
while (iter.get()) {
Iter next = iter;
next.next();
this->remove(iter.get());
iter = next;
}
SkASSERT(0 == fCount || -1 == fCount);
this->validate();
}
int count() const { return SkTMax(fCount ,0); }
bool isEmpty() const { this->validate(); return 0 == fCount || -1 == fCount; }
bool operator== (const SkTLList& list) const {
if (this == &list) {
return true;
}
// Call count() rather than use fCount because an empty list may have fCount = 0 or -1.
if (this->count() != list.count()) {
return false;
}
for (Iter a(*this, Iter::kHead_IterStart), b(list, Iter::kHead_IterStart);
a.get();
a.next(), b.next()) {
SkASSERT(b.get()); // already checked that counts match.
if (!(*a.get() == *b.get())) {
return false;
}
}
return true;
}
bool operator!= (const SkTLList& list) const { return !(*this == list); }
/** The iterator becomes invalid if the element it refers to is removed from the list. */
class Iter : private NodeList::Iter {
private:
typedef typename NodeList::Iter INHERITED;
public:
typedef typename INHERITED::IterStart IterStart;
//!< Start the iterator at the head of the list.
static const IterStart kHead_IterStart = INHERITED::kHead_IterStart;
//!< Start the iterator at the tail of the list.
static const IterStart kTail_IterStart = INHERITED::kTail_IterStart;
Iter() {}
Iter(const SkTLList& list, IterStart start = kHead_IterStart) {
INHERITED::init(list.fList, start);
}
T* init(const SkTLList& list, IterStart start = kHead_IterStart) {
return this->nodeToObj(INHERITED::init(list.fList, start));
}
T* get() { return this->nodeToObj(INHERITED::get()); }
T* next() { return this->nodeToObj(INHERITED::next()); }
T* prev() { return this->nodeToObj(INHERITED::prev()); }
Iter& operator= (const Iter& iter) { INHERITED::operator=(iter); return *this; }
private:
friend class SkTLList;
Node* getNode() { return INHERITED::get(); }
T* nodeToObj(Node* node) {
if (node) {
return reinterpret_cast<T*>(node->fObj);
} else {
return nullptr;
}
}
};
private:
struct Block {
int fNodesInUse;
Node fNodes[N];
};
void delayedInit() {
SkASSERT(-1 == fCount);
fFirstBlock.fNodesInUse = 0;
for (unsigned int i = 0; i < N; ++i) {
fFreeList.addToHead(fFirstBlock.fNodes + i);
fFirstBlock.fNodes[i].fBlock = &fFirstBlock;
}
fCount = 0;
this->validate();
}
Node* createNode() {
if (-1 == fCount) {
this->delayedInit();
}
Node* node = fFreeList.head();
if (node) {
fFreeList.remove(node);
++node->fBlock->fNodesInUse;
} else {
// Should not get here when count == 0 because we always have the preallocated first
// block.
SkASSERT(fCount > 0);
Block* block = reinterpret_cast<Block*>(sk_malloc_throw(sizeof(Block)));
node = &block->fNodes[0];
new (node) Node;
node->fBlock = block;
block->fNodesInUse = 1;
for (unsigned int i = 1; i < N; ++i) {
new (block->fNodes + i) Node;
fFreeList.addToHead(block->fNodes + i);
block->fNodes[i].fBlock = block;
}
}
++fCount;
return node;
}
void removeNode(Node* node) {
SkASSERT(node);
fList.remove(node);
SkTCast<T*>(node->fObj)->~T();
Block* block = node->fBlock;
// Don't ever elease the first block, just add its nodes to the free list
if (0 == --block->fNodesInUse && block != &fFirstBlock) {
for (unsigned int i = 0; i < N; ++i) {
if (block->fNodes + i != node) {
fFreeList.remove(block->fNodes + i);
}
block->fNodes[i].~Node();
}
sk_free(block);
} else {
fFreeList.addToHead(node);
}
--fCount;
this->validate();
}
void validate() const {
#ifdef SK_DEBUG
bool isEmpty = false;
if (-1 == fCount) {
// We should not yet have initialized the free list.
SkASSERT(fFreeList.isEmpty());
isEmpty = true;
} else if (0 == fCount) {
// Should only have the nodes from the first block in the free list.
SkASSERT(fFreeList.countEntries() == N);
isEmpty = true;
}
SkASSERT(isEmpty == fList.isEmpty());
fList.validate();
fFreeList.validate();
typename NodeList::Iter iter;
Node* freeNode = iter.init(fFreeList, Iter::kHead_IterStart);
while (freeNode) {
SkASSERT(fFreeList.isInList(freeNode));
Block* block = freeNode->fBlock;
// Only the first block is allowed to have all its nodes in the free list.
SkASSERT(block->fNodesInUse > 0 || block == &fFirstBlock);
SkASSERT((unsigned)block->fNodesInUse < N);
int activeCnt = 0;
int freeCnt = 0;
for (unsigned int i = 0; i < N; ++i) {
bool free = fFreeList.isInList(block->fNodes + i);
bool active = fList.isInList(block->fNodes + i);
SkASSERT(free != active);
activeCnt += active;
freeCnt += free;
}
SkASSERT(activeCnt == block->fNodesInUse);
freeNode = iter.next();
}
int count = 0;
Node* activeNode = iter.init(fList, Iter::kHead_IterStart);
while (activeNode) {
++count;
SkASSERT(fList.isInList(activeNode));
Block* block = activeNode->fBlock;
SkASSERT(block->fNodesInUse > 0 && (unsigned)block->fNodesInUse <= N);
int activeCnt = 0;
int freeCnt = 0;
for (unsigned int i = 0; i < N; ++i) {
bool free = fFreeList.isInList(block->fNodes + i);
bool active = fList.isInList(block->fNodes + i);
SkASSERT(free != active);
activeCnt += active;
freeCnt += free;
}
SkASSERT(activeCnt == block->fNodesInUse);
activeNode = iter.next();
}
SkASSERT(count == fCount || (0 == count && -1 == fCount));
#endif
}
NodeList fList;
NodeList fFreeList;
Block fFirstBlock;
int fCount;
};
#endif