阅读Sofia-SIP源码 - su模块 - su_alloc.c/h

在众多资料和文章中多次注意到出现了home based memory management。这应该是Sofia软件包的亮点之一。现在总算开始分析它了。

struct su_home_s {
  int         suh_size;
  su_block_t *suh_blocks;
  su_alock_t *suh_lock;
};

typedef struct {
  unsigned sua_size:SIZEBITS;	/**< Size of the block */
  unsigned sua_home:1;		/**< Is this another home? */
  unsigned :0;
  void    *sua_data;		/**< Data pointer */
} su_alloc_t;

struct su_block_s {
  su_home_t  *sub_parent;	/**< Parent home */
  char       *sub_preload;	/**< Preload area */
  su_home_stat_t *sub_stats;	/**< Statistics.. */
  void      (*sub_destructor)(void *); /**< Destructor function */
  size_t      sub_ref;		/**< Reference count */
#define REF_MAX SIZE_MAX
  size_t      sub_used;		/**< Number of blocks allocated */
  size_t      sub_n;		/**< Size of hash table  */

  unsigned    sub_prsize:16;	/**< Preload size */
  unsigned    sub_prused:16;	/**< Used from preload */
  unsigned    sub_hauto:1;      /**< "Home" is not from malloc */
  unsigned    sub_auto:1;	/**< struct su_block_s is not from malloc */
  unsigned    sub_preauto:1;	/**< Preload is not from malloc */
  unsigned    sub_auto_all:1;	/**< Everything is from stack! */
  unsigned :0;

  su_alloc_t  sub_nodes[SUB_N];	/**< Pointers to data/lower blocks */
};

从结构体类型来看，整个Home based memory management包括三个层级。最上层是su_home_s，中间一层是su_block_s，最下那层是su_alloc_t。su_home_s结构体保留一个指向su_block_s结构体的指针，su_block_s包含一个su_alloc_t类型的数组。

SU_HOME_INIT宏定义就是给一个su_home_s结构体变量赋初值。

#define SU_HOME_INIT(obj) { 0, NULL, NULL }

su.c源文件中的前部包含了一大段有关如何使用ho