nginx源码初读（3）--让烦恼从main开始ngx_pool

<code><span>typedef</span><span>struct</span> ngx_pool_s        ngx_pool_t;

<span>typedef</span><span>struct</span> ngx_pool_cleanup_s  ngx_pool_cleanup_t;
<span>typedef</span><span>void</span> (*ngx_pool_cleanup_pt)(<span>void</span> *data);
<span>struct</span> ngx_pool_cleanup_s {
    ngx_pool_cleanup_pt   handler;
    <span>void</span>                 *data;
    ngx_pool_cleanup_t   *next;
};

<span>typedef</span><span>struct</span> ngx_pool_large_s  ngx_pool_large_t;
<span>struct</span> ngx_pool_large_s {
    ngx_pool_large_t     *next;
    <span>void</span>                 *alloc;
};

<span>typedef</span><span>struct</span> {
    u_char               *last;
    u_char               *end;
    <span>/* 分别指当前内存池的分配位置（下次从last分配内存）和结束位置（内存用光啦）
     * if ((size_t) (p->d.end - m) >= size) {
           p->d.last = m + size;
           return m;
       }  
     */</span>    ngx_pool_t           *next;
    <span>/* 指向下一个pool内存块（当pool内存不足的时候会调用palloc_block来创建一块新的pool并分配内存）
     * psize = (size_t) (pool->d.end - (u_char *) pool);
       m = ngx_memalign(NGX_POOL_ALIGNMENT, psize, pool->log);
       new = (ngx_pool_t *) m;
       p->d.next = new;
     */</span>    ngx_uint_t            failed; 
    <span>/* 当前block内存分配失败次数，从这段代码看应该current是用来记录要创建内存块的搜索位置？
       因为它记录了从这一块开始内存不够用，而failed是为了重定向current而存在的，减少遍历数量（在4以内）
     * for (p = pool->current; p->d.next; p = p->d.next) {
          if (p->d.failed++ > 4) {
              pool->current = p->d.next;
          }
       }
     */</span>
} ngx_pool_data_t;


<span>struct</span> ngx_pool_s {
    ngx_pool_data_t       d;
    size_t                max;
    ngx_pool_t           *current;
    ngx_chain_t          *chain;
    ngx_pool_large_t     *large;
    ngx_pool_cleanup_t   *cleanup;
    ngx_log_t            *<span>log</span>;
};
</code>