ref.h

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/*
 * SPDX-FileCopyrightText: Copyright The Zephyr Project Contributors
 * SPDX-License-Identifier: Apache-2.0
 */

 
#ifndef ZEPHYR_INCLUDE_SYS_REF_H_
#define ZEPHYR_INCLUDE_SYS_REF_H_
 
#include <limits.h>
#include <stdbool.h>
 
#include <zephyr/sys/atomic.h>
#include <zephyr/sys/__assert.h>
 
#ifdef __cplusplus
extern "C" {
#endif


#define SYS_REFCOUNT_SATURATED  LONG_MAX

struct sys_refcount {
        atomic_t value;
};

#define SYS_REFCOUNT_INITIALIZER { .value = ATOMIC_INIT(1) }

static inline void sys_refcount_init(struct sys_refcount *const rc)
{
        atomic_set(&rc->value, 1);
}

static inline void sys_refcount_inc(struct sys_refcount *const rc)
{
        atomic_val_t old = atomic_get(&rc->value);
 
        while (true) {
                __ASSERT(old != 0, "Increment of zero reference counter");
 
                if (old == SYS_REFCOUNT_SATURATED) {
                        return;
                }
 
                if (atomic_cas(&rc->value, old, old + 1)) {
                        return;
                }
 
                old = atomic_get(&rc->value);
        }
}

static inline bool sys_refcount_dec(struct sys_refcount *const rc)
{
        atomic_val_t old = atomic_get(&rc->value);
 
        while (true) {
                if (old == SYS_REFCOUNT_SATURATED) {
                        return false;
                }
 
                __ASSERT(old > 0, "Decrement of zero reference counter");
 
                if (atomic_cas(&rc->value, old, old - 1)) {
                        return old == 1;
                }
 
                old = atomic_get(&rc->value);
        }
}
 
struct sys_ref;

typedef void (*sys_ref_release_t)(struct sys_ref *const ref);

struct sys_ref {
        struct sys_refcount refcount;
};

#define SYS_REF_INITIALIZER { .refcount = SYS_REFCOUNT_INITIALIZER }

static inline void sys_ref_init(struct sys_ref *const ref)
{
        sys_refcount_init(&ref->refcount);
}

static inline void sys_ref_get(struct sys_ref *const ref)
{
        sys_refcount_inc(&ref->refcount);
}

static inline bool sys_ref_put(struct sys_ref *const ref,
                               const sys_ref_release_t release)
{
        __ASSERT_NO_MSG(release != NULL);
 
        if (sys_refcount_dec(&ref->refcount)) {
                release(ref);
                return true;
        }
 
        return false;
}

 
#ifdef __cplusplus
}
#endif
 
#endif /* ZEPHYR_INCLUDE_SYS_REF_H_ */