#pragma omp

#define LRWL_WRITE_ACTIVE (1UL<<31)
#define LRWL_MASK (LRWL_WRITE_ACTIVE - 1)
#define LRWL_MAX_READERS 1024

typedef struct LRWL {
	_Atomic uint32_t data;
} LRWL;

static inline void lrwl_read_lock(LRWL *self) {
	while(1) {
		uint32_t data = atomic_load(&self->data);
		
		if((data & LRWL_WRITE_ACTIVE) || (data & LRWL_MASK) >= LRWL_MAX_READERS) {
			continue;
		}
		
		if(atomic_compare_exchange_weak(&self->data, &data, data + 1)) {
			return;
		}
	}
}

static inline void lrwl_read_unlock(LRWL *self) {
	while(1) {
		uint32_t data = atomic_load(&self->data);
		
		assert((data & LRWL_MASK) > 0);
		
		if(atomic_compare_exchange_weak(&self->data, &data, data - 1)) {
			return;
		}
	}
}

static inline void lrwl_write_lock(LRWL *self) {
	while(1) {
		uint32_t data = atomic_load(&self->data);
		
		if(data & LRWL_WRITE_ACTIVE) {
			continue;
		}
		
		if(atomic_compare_exchange_weak(&self->data, &data, data | LRWL_WRITE_ACTIVE)) {
			while((atomic_load(&self->data) & LRWL_MASK) > 0);
			
			return;
		}
	}
}

static inline void lrwl_write_unlock(LRWL *self) {
	while(1) {
		uint32_t data = atomic_load(&self->data);
		
		assert(data & LRWL_WRITE_ACTIVE);
		
		if(atomic_compare_exchange_weak(&self->data, &data, data & ~LRWL_WRITE_ACTIVE)) {
			return;
		}
	}
}