ngx_palloc.h 和 ngx_palloc.c主要用于nginx管理內存池

#include <ngx_config.h>
#include <ngx_core.h>


/*
 * NGX_MAX_ALLOC_FROM_POOL should be (ngx_pagesize - 1), i.e. 4095 on x86.
 * On Windows NT it decreases a number of locked pages in a kernel.
 */
#define NGX_MAX_ALLOC_FROM_POOL  (ngx_pagesize - 1)
//內存池默認大小
#define NGX_DEFAULT_POOL_SIZE    (16 * 1024)

//#define ngx_align(d, a)     (((d) + (a - 1)) & ~(a - 1)) 將d向上取a的倍數。

#define NGX_POOL_ALIGNMENT       16
//內存池的最小大小，為16的倍數
#define NGX_MIN_POOL_SIZE                                                     \
    ngx_align((sizeof(ngx_pool_t) + 2 * sizeof(ngx_pool_large_t)),            \
              NGX_POOL_ALIGNMENT)

//ngx_pool_cleanup_pt 為函數指針
typedef void (*ngx_pool_cleanup_pt)(void *data);

typedef struct ngx_pool_cleanup_s  ngx_pool_cleanup_t;
//這個結構用來表示內存池中的數據的清理handler
//handler表示清理函數，data表示傳遞給清理函數的數據，next表示下一個清理handler,
//也就是說當destroy這個pool的時候會遍歷清理handler鏈表，然后調用handler.
struct ngx_pool_cleanup_s {
    ngx_pool_cleanup_pt   handler;
    void                 *data;
    ngx_pool_cleanup_t   *next;
};


typedef struct ngx_pool_large_s  ngx_pool_large_t;
//該結構表示大塊內存，這個結構很簡單，就是一個指針指向下一塊large，一個alloc指向數據
struct ngx_pool_large_s {
    ngx_pool_large_t     *next;
    void                 *alloc;
};

//數據區的指針ngx_pool_data_t。其中last表示當前的數據區的已經使用的數據的結尾。
//end表示當前的內存池的結尾。也就是說end-last就是內存池未使用的大小。
typedef struct {
    u_char               *last;
    u_char               *end;
//指向下一塊內存池
    ngx_pool_t           *next;
//申請該內存池失敗的標記
    ngx_uint_t            failed;
} ngx_pool_data_t;


struct 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            *log;
};


typedef struct {
    ngx_fd_t              fd;
    u_char               *name;
    ngx_log_t            *log;
} ngx_pool_cleanup_file_t;


void *ngx_alloc(size_t size, ngx_log_t *log);
void *ngx_calloc(size_t size, ngx_log_t *log);

ngx_pool_t *ngx_create_pool(size_t size, ngx_log_t *log);
void ngx_destroy_pool(ngx_pool_t *pool);
void ngx_reset_pool(ngx_pool_t *pool);

void *ngx_palloc(ngx_pool_t *pool, size_t size);
void *ngx_pnalloc(ngx_pool_t *pool, size_t size);
void *ngx_pcalloc(ngx_pool_t *pool, size_t size);
void *ngx_pmemalign(ngx_pool_t *pool, size_t size, size_t alignment);
ngx_int_t ngx_pfree(ngx_pool_t *pool, void *p);


ngx_pool_cleanup_t *ngx_pool_cleanup_add(ngx_pool_t *p, size_t size);
void ngx_pool_run_cleanup_file(ngx_pool_t *p, ngx_fd_t fd);
void ngx_pool_cleanup_file(void *data);
void ngx_pool_delete_file(void *data);


#endif /* _NGX_PALLOC_H_INCLUDED_ */