c 对象池

发表于 更新于

编译要求

需要 gcc, 版本 >= 4.7.2, 支持 __atomic* 内建同步函数

(理论上有 ABA 问题

lpool.h

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#ifndef _LPOOL_H_
#define _LPOOL_H_

struct lpool_node {
    struct lpool_node *next;
};

struct lpool {
    struct lpool_node *root;
    struct lpool_node *(*alloc)();
    void (*free)(struct lpool_node *n);
};

void lpool_clear(struct lpool *p);
struct lpool_node *lpool_get(struct lpool *p);
void lpool_put(struct lpool *p, struct lpool_node *n);

#endif /* !_LPOOL_H_ */

lpool.c

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#include "lpool.h"
#include <stddef.h>

#define atomic_swap(p, v) __atomic_exchange_n((p), (v), __ATOMIC_ACQ_REL);
#define atomic_cas(p, pc, v) __atomic_compare_exchange_n((p), (pc), v, 1, __ATOMIC_ACQ_REL, __ATOMIC_RELAXED)

void lpool_clear(struct lpool *p)
{
    struct lpool_node *n;
    struct lpool_node *t;

    n = atomic_swap(&p->root, NULL);
    while (n != NULL) {
        t = n;
        n = n->next;
        p->free(t);
    }
}

struct lpool_node *lpool_get(struct lpool *p)
{
    struct lpool_node *n;

    for (n = p->root; n != NULL; n = p->root) {
        if (atomic_cas(&p->root, &n, n->next)) {
            break;
        }
    }
    if (n == NULL) {
        n = p->alloc();
    }
    n->next = NULL;
    return n;
}

void lpool_put(struct lpool *p, struct lpool_node *n)
{
    do {
        n->next = p->root;
    } while (!atomic_cas(&p->root, &n->next, n));
}