Make block size a template parameter of SkTLList

src/core/SkTLList.h

 /*
  * 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 "SkTypes.h"
 #include <utility>
 
-template <typename T> class SkTLList;
-template <typename T>
-inline void* operator new(size_t, SkTLList<T>* list,
-                          typename SkTLList<T>::Placement placement,
-                          const typename SkTLList<T>::Iter& location);
-
 /** 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>
-class SkTLList : SkNoncopyable {
+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;
 
-    /** 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. */
-    SkTLList(int allocCnt = 1) : fCount(0), fAllocCnt(allocCnt) {
-        SkASSERT(allocCnt > 0);
+    SkTLList() : fCount(0) {
         this->validate();
     }
 
     ~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 (int i = 0; i < fAllocCnt; ++i) {
+                for (unsigned int i = 0; i < N; ++i) {
                     block->fNodes[i].~Node();
                 }
                 sk_free(block);
             }
         }
     }
 
     /** Adds a new element to the list at the head. */
     template <typename... Args> T* addToHead(Args&&... args) {
         this->validate();
@@ skipping 141 matching lines @@
                 return reinterpret_cast<T*>(node->fObj);
             } else {
                 return nullptr;
             }
         }
     };
 
 private:
     struct Block {
         int fNodesInUse;
-        Node fNodes[1];
+        Node fNodes[N];
     };
 
-    size_t blockSize() const { return sizeof(Block) + sizeof(Node) * (fAllocCnt-1); }
-
     Node* createNode() {
         Node* node = fFreeList.head();
         if (node) {
             fFreeList.remove(node);
             ++node->fBlock->fNodesInUse;
         } else {
-            Block* block = reinterpret_cast<Block*>(sk_malloc_throw(this->blockSize()));
+            Block* block = reinterpret_cast<Block*>(sk_malloc_throw(sizeof(Block)));
             node = &block->fNodes[0];
             new (node) Node;
             node->fBlock = block;
             block->fNodesInUse = 1;
-            for (int i = 1; i < fAllocCnt; ++i) {
+            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();
         if (0 == --node->fBlock->fNodesInUse) {
             Block* block = node->fBlock;
-            for (int i = 0; i < fAllocCnt; ++i) {
+            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
         SkASSERT((0 == fCount) == fList.isEmpty());
         SkASSERT((0 != fCount) || fFreeList.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;
-            SkASSERT(block->fNodesInUse > 0 && block->fNodesInUse < fAllocCnt);
+            SkASSERT(block->fNodesInUse > 0 && (unsigned)block->fNodesInUse < N);
 
             int activeCnt = 0;
             int freeCnt = 0;
-            for (int i = 0; i < fAllocCnt; ++i) {
+            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 && block->fNodesInUse <= fAllocCnt);
+            SkASSERT(block->fNodesInUse > 0 && (unsigned)block->fNodesInUse <= N);
 
             int activeCnt = 0;
             int freeCnt = 0;
-            for (int i = 0; i < fAllocCnt; ++i) {
+            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);
 #endif
     }
 
     NodeList fList;
     NodeList fFreeList;
     int fCount;
-    int fAllocCnt;
-
 };
 
 #endif