POOL

#ifndef POOL_HHH
#define POOL_HHH

#include "common.h"

/* simple and fast obj pool without multi-thread support */

typedef uint32_t pool_size_t;
typedef uint32_t pool_obj_size_t;

typedef struct pool {

pool_obj_size_t objsize;
pool_obj_size_t objmemsize;

pool_size_t num;

pool_size_t free_idx;    /* free list implemented by array */
pool_size_t *freeobj;    /* free list array */

void *obj;     /* obj array */
char buffer[0];
} pool_t;

typedef struct pool_obj_head {
pool_t *p;

} pool_obj_head_t;

pool_t *pool_create(pool_obj_size_t objsize, pool_size_t poolsize);

void *pool_alloc_obj(pool_t * p);

void pool_free_obj(pool_t * p, void *obj);

void pool_destory(pool_t * p);

#endif

#include "common.h"
#include "pool.h"
#include <assert.h>

static inline void *objmem_to_obj(void *objmem)
{
    return objmem + sizeof(pool_obj_head_t);
}

static inline void *obj_to_objmem(void *obj)
{
    return obj - sizeof(pool_obj_head_t);
}

static inline void *idx_to_objmem(pool_t * p, pool_size_t idx)
{
    return p->obj + idx * (p->objmemsize);
}

static inline pool_size_t objmem_to_idx(pool_t * p, void *obj)
{
    return (obj - p->obj) / (p->objmemsize);
}

pool_t *pool_create(pool_obj_size_t objsize, pool_size_t poolsize)
{

    pool_size_t i;
    pool_obj_head_t *head;

    pool_t *p;

    size_t manage_mem_size = (sizeof(pool_t));
    size_t free_list_mem_size = (poolsize * sizeof(pool_size_t));
    size_t obj_mem_size = (objsize + sizeof(pool_obj_head_t)) * poolsize;

    p = calloc(manage_mem_size + free_list_mem_size + obj_mem_size, 1);

    if (!p)
        return NULL;

    p->num = poolsize;
    p->objsize = objsize;
    p->objmemsize = obj_mem_size / poolsize;
    p->freeobj = (void *)p->buffer;
    p->obj = p->buffer + free_list_mem_size;

    /* init free list */
    p->free_idx = 0;
    for (i = 0; i < p->num; i++) {
        p->freeobj[i] = i + 1;
    }

    /* init obj head */
    for (i = 0; i < p->num; i++) {
        head = (pool_obj_head_t *) (idx_to_objmem(p, i));
        head->p = p;
    }
    return p;
}

void *pool_alloc_obj(pool_t * p)
{
    pool_size_t idx;
    void *obj;

    if (unlikely(p->free_idx == p->num)) {
        return NULL;    /* empty */
    }

    idx = p->free_idx;
    p->free_idx = p->freeobj[idx];

    obj = idx_to_objmem(p, idx);

    return objmem_to_obj(obj);
}

void pool_free_obj(pool_t * p, void *obj)
{

    pool_size_t idx;
    pool_obj_head_t *head;

    head = (pool_obj_head_t *) obj_to_objmem(obj);

    assert(head->p == p);

    idx = objmem_to_idx(p, obj);

    /* insert to list head, hot cache */
    p->freeobj[idx] = p->free_idx;
    p->free_idx = idx;
}

void pool_destory(pool_t * p)
{
    free(p);
}