Nginx源码阅读（ngx_list_t）

/* src/core/ngx_list.h */

typedef struct ngx_list_part_s  ngx_list_part_t;

struct ngx_list_part_s {
    void             *elts; // 数组的首地址
    ngx_uint_t        nelts; // 数组中已经使用的元素个数
    ngx_list_part_t  *next;
};


typedef struct {
    ngx_list_part_t  *last; // 指向最后一个ngx_list_part_t
    ngx_list_part_t   part; // 第一个ngx_list_part_t
    size_t            size; // 每个数组元素占用的字节数
    ngx_uint_t        nalloc; // 数组中能够容纳的最大元素个数
    ngx_pool_t       *pool;
} ngx_list_t;


ngx_list_t *ngx_list_create(ngx_pool_t *pool, ngx_uint_t n, size_t size);

// 初始化一个链表
static ngx_inline ngx_int_t
ngx_list_init(ngx_list_t *list, ngx_pool_t *pool, ngx_uint_t n, size_t size)
{
    list->part.elts = ngx_palloc(pool, n * size);
    if (list->part.elts == NULL) {
        return NGX_ERROR;
    }

    list->part.nelts = 0;
    list->part.next = NULL;
    list->last = &list->part;
    list->size = size;
    list->nalloc = n;
    list->pool = pool;

    return NGX_OK;
}


/*
 *
 *  the iteration through the list:
 *
 *  part = &list.part;
 *  data = part->elts;
 *
 *  for (i = 0 ;; i++) {
 *
 *      if (i >= part->nelts) {
 *          if (part->next == NULL) {
 *              break;
 *          }
 *
 *          part = part->next;
 *          data = part->elts;
 *          i = 0;
 *      }
 *
 *      ...  data[i] ...
 *
 *  }
 */


void *ngx_list_push(ngx_list_t *list);

/* src/core/ngx_list.c */

// 创建并初始化一个链表
ngx_list_t *
ngx_list_create(ngx_pool_t *pool, ngx_uint_t n, size_t size)
{
    ngx_list_t  *list;

    list = ngx_palloc(pool, sizeof(ngx_list_t));
    if (list == NULL) {
        return NULL;
    }

    if (ngx_list_init(list, pool, n, size) != NGX_OK) {
        return NULL;
    }

    return list;
}


// 向链表中添加新元素，返回新元素的地址
void *
ngx_list_push(ngx_list_t *l)
{
    void             *elt;
    ngx_list_part_t  *last;

    last = l->last;

    if (last->nelts == l->nalloc) {

        /* the last part is full, allocate a new list part */

        last = ngx_palloc(l->pool, sizeof(ngx_list_part_t));
        if (last == NULL) {
            return NULL;
        }

        last->elts = ngx_palloc(l->pool, l->nalloc * l->size);
        if (last->elts == NULL) {
            return NULL;
        }

        last->nelts = 0;
        last->next = NULL;

        l->last->next = last;
        l->last = last;
    }

    elt = (char *) last->elts + l->size * last->nelts;
    last->nelts++;

    return elt;
}