ngx_pool_t *

ngx_create_pool(size_t size, ngx_log_t *log)

{

    ngx_pool_t *p;

    p = ngx_memalign(NGX_POOL_ALIGNMENT, size, log);//间接调用了posix_memalign分配内存

    if (p == NULL) {

        return NULL;

    }

    p->d.last = (u_char *) p + sizeof(ngx_pool_t);//初始的前面几个字节用于储存内存池头部信息,所以下一次分配的开始应该前移头部的大小

    p->d.end = (u_char *) p + size;//内存池节点的结尾

    p->d.next = NULL;//由于当前内存池只有一个节点所以next为NULL

    p->d.failed = 0;

    size = size - sizeof(ngx_pool_t);

    p->max = (size < NGX_MAX_ALLOC_FROM_POOL) ? size : NGX_MAX_ALLOC_FROM_POOL;//设置小块内存和大块内存的判断标准

    p->current = p;

    p->chain = NULL;

    p->large = NULL;

    p->cleanup = NULL;

    p->log = log;

    return p;

}

void *

ngx_palloc(ngx_pool_t *pool, size_t size)

{

    u_char *m;

    ngx_pool_t *p;

    if (size <= pool->max) //判断是小块内存 还是大块内存

    {

        p = pool->current;

        do {

            m = ngx_align_ptr(p->d.last, NGX_ALIGNMENT);

            if ((size_t) (p->d.end - m) >= size) {//尝试在已有的内存池节点中分配内存

                p->d.last = m + size;

                return m;

            }

            p = p->d.next;

        } while (p);

        return ngx_palloc_block(pool, size);//当前已有节点都分配失败，创建一个新的内存池节点

    }

    return ngx_palloc_large(pool, size);//分配大块内存

}

void

ngx_destroy_pool(ngx_pool_t *pool)

{

    ngx_pool_t *p, *n;

    ngx_pool_large_t *l;

    ngx_pool_cleanup_t *c;

    for (c = pool->cleanup; c; c = c->next) {

        if (c->handler) {

            ngx_log_debug1(NGX_LOG_DEBUG_ALLOC, pool->log, 0,"run cleanup: %p", c);

            c->handler(c->data);//调用需要在内存池释放时同步调用的方法

        }

    }

    for (l = pool->large; l; l = l->next) {//释放大块内存

        ngx_log_debug1(NGX_LOG_DEBUG_ALLOC, pool->log, 0, "free: %p", l->alloc);

        if (l->alloc) {

           ngx_free(l->alloc);

        }

    }

    #if (NGX_DEBUG)

    /*

    * we could allocate the pool->log from this pool

    * so we cannot use this log while free()ing the pool

    */

    for (p = pool, n = pool->d.next; /* void */; p = n, n = n->d.next) {

        ngx_log_debug2(NGX_LOG_DEBUG_ALLOC, pool->log, 0,"free: %p, unused: %uz", p, p->d.end - p->d.last);

        if (n == NULL) {

            break;

        }

    }

    #endif

    for (p = pool, n = pool->d.next; /* void */; p = n, n = n->d.next) {

        ngx_free(p);//间接调用free释放内存

        if (n == NULL) {

            break;

        }

    }

}