Nginx dynamic array ngx_array_t

: This article mainly introduces nginx dynamic array ngx_array_t. if you are interested in the PHP Tutorial, refer to it. Ngx_array_t is a dynamic array designed in nginx, similar to the vector in STL . The following is an example analysis.

I. instances

# Include
  
   
# Include "ngx_config.h" # include "ngx_conf_file.h" # include "nginx. h "# include" ngx_core.h "# include" ngx_string.h "# include" ngx_palloc.h "# include" volume "volatile cycle * ngx_cycle; void cycle (volume level, ngx_log_t * log, ngx_err_t err, const char * fmt ,...) {} void dump_pool (ngx_pool_t * pool) {while (pool) {printf ("pool = 0x % x \ n", pool); printf (". d \ n "); printf (". last = 0x % x \ n ", pool-> d. last); printf (". end = 0x % x \ n ", pool-> d. end); printf (". next = 0x % x \ n ", pool-> d. next); printf (". failed = % d \ n ", pool-> d. failed); printf (". max = % d \ n ", pool-> max); printf (". current = 0x % x \ n ", pool-> current); printf (". chain = 0x % x \ n ", pool-> chain); printf (". large = 0x % x \ n ", pool-> large); printf (". cleanup = 0x % x \ n ", pool-> cleanup); printf (". log = 0x % x \ n ", pool-> log); printf (" available pool memory = % d \ n ", pool-> d. end-pool-> d. last); ngx_pool_large_t * large = pool-> large; printf ("****** large_pool ******* \ n"); while (large) {printf ("% p->", large); large = large-> next;} printf ("\ n"); pool = pool-> d. next ;}} typedef struct {intarray [128]; // 128*4 = 512} TestNode; int main () {ngx_pool_t * pool; printf ("-------------------------------- \ n "); printf ("create a new pool: \ n"); printf ("-------------------------------- \ n"); pool = ngx_create_pool (1024, NULL); dump_pool (pool ); ngx_array_t * myArray = ngx_array_create (pool, 1, sizeof (TestNode )); printf ("******** ngx_array_create *********** \ n"); dump_pool (pool); TestNode * t1 = ngx_array_push (myArray ); testNode * t2 = ngx_array_push (myArray); printf ("******** ngx_array_push *********** \ n"); dump_pool (pool ); ngx_array_destroy (myArray); // nothing is done here dump_pool (pool); ngx_destroy_pool (pool); return 0 ;}
  

Running result:

--------------------------------create a new pool:--------------------------------pool = 0x95ae020  .d   .last = 0x95ae048   .end = 0x95ae420   .next = 0x0   .failed = 0 .max = 984 .current = 0x95ae020  .chain= 0x0 .large = 0x0 .cleanup = 0x0 .log = 0x0available pool memory = 984 *****large_pool*******NULL******ngx_array_create**********pool = 0x95ae020  .d   .last = 0x95ae25c   .end = 0x95ae420   .next = 0x0   .failed = 0 .max = 984 .current = 0x95ae020 .chain = 0x0 .large = 0x0 .cleanup = 0x0 .log = 0x0available pool memory = 452 *****large_pool*******NULL******ngx_array_push**********pool = 0x95ae020  .d   .last = 0x95ae264   .end = 0x95ae420   .next = 0x0    .failed = 0 .max = 984 .current = 0x95ae020 .chain = 0x0 .large = 0x95ae25c .cleanup = 0x0 .log = 0x0available pool memory = 444 *****large_pool*******0x95ae25c->NULL******ngx_array_destroy******pool = 0x95ae020  .d   .last = 0x95ae264   .end = 0x95ae420   .next = 0x0   .failed = 0 .max = 984 .current = 0x95ae020 .chain = 0x0 .large = 0x95ae25c .cleanup = 0x0 .log = 0x0available pool memory = 444 *****large_pool*******0x95ae25c->NULL

1. we can see from the changes in the available pool memory that the memory occupied by the ngx_array_t and ngx_pool_large_t struct is allocated to the memory pool.

It can be proved from the source code:

Ngx_array_t *

Ngx_array_create (ngx_pool_t * p, ngx_uint_t n, size_t size)

{

A = ngx_palloc (p, sizeof (ngx_array_t ));

}

Static void *

Ngx_palloc_large (ngx_pool_t * pool, size_t size)

{

// Allocate it on the memory pool.

Large = ngx_palloc (pool, sizeof (ngx_pool_large_t ));

}

2. if ngx_array_push is scaled up, the occupied memory will not be released. You can refer to the source code of ngx_array_push and will not post it here.

3. if the size of the allocated dynamic array exceeds the capacity of a memory pool (1024 in this example), ngx_palloc_large will be called to allocate large memory blocks.

4. if the memory occupied by the dynamic array is a large block of memory, ngx_array_destroy will not do anything, and this API has not been called in the nginx kernel source code.

For compilation, refer to the previous article on analyzing the ngx_queue_t struct.

II. references:

Tao Hui, an in-depth understanding of nginx

Http://blog.csdn.net/livelylittlefish/article/details/6586946

The above describes the nginx dynamic array ngx_array_t, including the content, hope to be helpful to friends who are interested in PHP tutorials.