It is thread safe?

[paulocoutinhox]

Hi,

It is thread-safe?

Thanks.

[paulocoutinhox]

Hi @mariusbancila,

Can you confirm this?

[ocbj]

Anyone? I hope to use this for generating resource ids. But I can't unless it's thread safe.

[ocbj]

So it isn't thread safe. The generator you provide is stored as a shared_ptr in uuid generator.

An easy workaround would be to use thread_local.
Here's what I went with:

inline uuids::uuid GenerateUuid(){
	thread_local std::unique_ptr<uuids::uuid_random_generator> uuidGenerator = nullptr;
	
	if(!uuidGenerator) {
		std::random_device rd;
		auto threadIdHash = std::hash<std::thread::id>{}(std::this_thread::get_id());
		uint64_t mixedSeed = static_cast<uint64_t>(rd()) ^ static_cast<uint64_t>(threadIdHash);
		
		thread_local std::mt19937 generator(static_cast<unsigned int>(mixedSeed));
		uuidGenerator = std::make_unique<uuids::uuid_random_generator>(generator);
	}
	
	auto& gen = *uuidGenerator.get();
	return gen();
}

For my use case the overhead of having one instance per thread is worth it, because it's not that much memory & I'm recycling threads in a thread pool. Hope this helps someone.