//fail { SharedPtr!long a = SharedPtr!long.make(123); SharedPtr!long b = SharedPtr!long.make(42); SharedPtr!long c = SharedPtr!long.make(666); a.compareExchange(b, c); assert(*a == 123); assert(*b == 123); assert(*c == 666); } //success { SharedPtr!long a = SharedPtr!long.make(123); SharedPtr!long b = a; SharedPtr!long c = SharedPtr!long.make(666); a.compareExchange(b, c); assert(*a == 666); assert(*b == 123); assert(*c == 666); } //shared fail { shared SharedPtr!(shared long) a = SharedPtr!(shared long).make(123); SharedPtr!(shared long) b = SharedPtr!(shared long).make(42); SharedPtr!(shared long) c = SharedPtr!(shared long).make(666); a.compareExchange(b, c); auto tmp = a.exchange(null); assert(*tmp == 123); assert(*b == 123); assert(*c == 666); } //shared success { SharedPtr!(shared long) b = SharedPtr!(shared long).make(123); shared SharedPtr!(shared long) a = b; SharedPtr!(shared long) c = SharedPtr!(shared long).make(666); a.compareExchange(b, c); auto tmp = a.exchange(null); assert(*tmp == 666); assert(*b == 123); assert(*c == 666); }
Compares the SharedPtr pointers pointed-to by this and expected.
If they are equivalent (store the same pointer value, and either share ownership of the same object or are both empty), assigns desired into this using the memory ordering constraints specified by success and returns true. If they are not equivalent, assigns this into expected using the memory ordering constraints specified by failure and returns false.
More info in c++ std::atomic<std::shared_ptr>.