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;
}