#include "pthread_impl.h"
#include <threads.h>

int __pthread_mutex_trylock(pthread_mutex_t *restrict m);

int mtx_trylock(mtx_t *restrict m) {
	if (m->_m_type == PTHREAD_MUTEX_NORMAL)
		return a_cas(&m->_m_lock, 0, EBUSY) & EBUSY;

	/* In the best of all worlds this is a tail call. */
	int ret = __pthread_mutex_trylock(m);
	switch (ret) {
	case 0:
		if (thrd_success == 0) break;
		else return thrd_success;
	case EBUSY:
		if (thrd_busy == EBUSY) break;
		else return thrd_busy;
	case EINVAL:
		if (thrd_error == EINVAL) break;
		else return thrd_error;
	}
	/* In case of UB may also return EPERM, EDEADLK or EAGAIN. EAGAIN is
	   specially tricky since C11 doesn't define how many recursive
	   calls can be done. (this *isn't* the maximum amount of nested
	   calls!) This implementation here deals this with a counter and
	   detects overflow, so this is definitively UB. */
	return ret;
}