text: // MIT License
  
  // Copyright (c) 2019 Erin Catto
  
  // Permission is hereby granted, free of charge, to any person obtaining a copy
  // of this software and associated documentation files (the "Software"), to deal
  // in the Software without restriction, including without limitation the rights
  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  // copies of the Software, and to permit persons to whom the Software is
  // furnished to do so, subject to the following conditions:
  
  // The above copyright notice and this permission notice shall be included in all
  // copies or substantial portions of the Software.
  
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  // SOFTWARE.
  
  #ifndef B2_BLOCK_ALLOCATOR_H
  #define B2_BLOCK_ALLOCATOR_H
  
  #include "b2_api.h"
  #include "b2_settings.h"
  
  // 可以申请块子节点大小的类型总数
  const int32 b2_blockSizeCount = 14;
  
  // 块子节点结构体[链表实现]声明
  struct b2Block;
  // 块结构体声明
  struct b2Chunk;
  
  /// This is a small object allocator used for allocating small
  /// objects that persist for more than one time step.
  /// See: http://www.codeproject.com/useritems/Small_Block_Allocator.asp
  class B2_API b2BlockAllocator
  {
  public:
  	b2BlockAllocator();
  	~b2BlockAllocator();
  
  	/// Allocate memory. This will use b2Alloc if the size is larger than b2_maxBlockSize.
  	void* Allocate(int32 size);
  
  	/// Free memory. This will use b2Free if the size is larger than b2_maxBlockSize.
  	void Free(void* p, int32 size);
  
  	void Clear();
  
  private:
      // 当前块的头指针(数组)
  	b2Chunk* m_chunks;
      // 当前已使用的块空间节点总数，通过m_chunks+小于m_chunkCount的偏移量i就可以找到第i+1个内存块
  	int32 m_chunkCount;
      // 当前已申请的块空间节点总数
  	int32 m_chunkSpace;
      // 保存了已经分配的页/块中还未被使用的块的开始地址的数组; 数组指针，每一个元素都是bBlock指针
  	b2Block* m_freeLists[b2_blockSizeCount];
  };
  
  #endif
  