#include "internal/ref_countable.h"

namespace google {

namespace api {

namespace expr {

namespace internal {

RefCountable::~RefCountable() { assert(unowned()); }

std::size_t RefCountable::owner_count() const {

return refcount_.load(std::memory_order_acquire);

}

bool RefCountable::single_owner() const {

// If we are the sole owner, only we have a view of the refcount, so no memory

// barrier needed.

return refcount_.load(std::memory_order_relaxed) == 1;

}

bool RefCountable::unowned() const {

// If refcounting is not being used, then this value must not have changed

// since construction. If refcounting is being used and this value is 0, then

// a call to unowned() is inherently racy all ready. So no memory barrier

// needed.

return refcount_.load(std::memory_order_relaxed) == 0;

}

void RefCountable::Ref() const {

refcount_.fetch_add(1, std::memory_order_relaxed);

}

bool RefCountable::Unref() const {

auto prev_value = refcount_.fetch_sub(1, std::memory_order_release);

assert(prev_value > 0);

if (prev_value == 1) {

std::atomic_thread_fence(std::memory_order_acquire);

return true;

}

return false;

}

} // namespace internal

} // namespace expr

} // namespace api

} // namespace google