libBLOC

/*
 * Copyright (C) 2023 Barry
 *
 * This file is part of Barry's Little Objects in C Library (libBLOC).
 *
 * libBLOC is free software: you can redistribute it and/or modify it under the
 * terms of the GNU General Public License as published by the Free Software
 * Foundation, either version 3 of the License, or (at your option) any later
 * version.
 *
 * libBLOC is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTIBILITY or FITNESS
 * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
 * details.
 *
 * You should have received a copy of the GNU General Public License along with
 * libBLOC.  If not, see <https://www.gnu.org/licenses/>.
 */

#ifdef __linux__
# define _GNU_SOURCE
# include <unistd.h>
#endif

#include <BLOC/object.h>
#include "../assert.h"
#include "object.h"

/* Get a unique identifier for the current thread */
static unsigned int
_obj_get_thread_id(void)
{
#if defined(__linux__)
	return (unsigned int) gettid();
#else
# error "No _obj_get_thread_id() for target platform"
#endif
}

/* Lock an object */
void
obj_lock(void *addr)
{
	struct ObjectHeader *obj = object_header(addr);
	ASSERT(obj->magic == OBJECT_MAGIC);
	unsigned int owner = _obj_get_thread_id();
	if (obj->owner != owner) {
		while (__atomic_test_and_set(&(obj->lock), __ATOMIC_ACQUIRE))
			__builtin_ia32_pause();
		obj->owner = owner;
	}
	__atomic_add_fetch(&obj->locks, 1, __ATOMIC_RELAXED);
}

/* Unlock an object */
void
obj_unlock(void *addr)
{
	struct ObjectHeader *obj = object_header(addr);
	ASSERT(obj->magic == OBJECT_MAGIC);
	if (__atomic_sub_fetch(&obj->locks, 1, __ATOMIC_RELAXED))
		return;
	__atomic_clear(&(obj->lock), __ATOMIC_RELEASE);
	obj->owner = 0;
}