Method GetRandomPeer

libi2pd/Transports.cpp:1151–1242

	template<typename Filter>
	std::shared_ptr<const i2p::data::RouterInfo> Transports::GetRandomPeer (Filter filter) const
	{
		if (m_Peers.empty()) return nullptr;
		auto ts = i2p::util::GetSecondsSinceEpoch ();
		bool found = false;
		i2p::data::IdentHash ident;
		{
			uint16_t inds[3];
			RAND_bytes ((uint8_t *)inds, sizeof (inds));
			std::lock_guard<std::mutex> l(m_PeersMutex);
			auto count = m_Peers.size ();
			if(count == 0) return nullptr;
			inds[0] %= count;
			auto it = m_Peers.begin ();
			std::advance (it, inds[0]);
			// try random peer
			if (it != m_Peers.end () && filter (it->second))
			{
				ident = it->first;
				found = true;
			}
			else
			{
				// try some peers around
				auto it1 = m_Peers.begin ();
				if (inds[0])
				{
					// before
					inds[1] %= inds[0];
					std::advance (it1, (inds[1] + inds[0])/2);
				}
				else
					it1 = it;
				auto it2 = it;
				if (inds[0] < m_Peers.size () - 1)
				{
					// after
					inds[2] %= (m_Peers.size () - 1 - inds[0]); inds[2] /= 2;
					std::advance (it2, inds[2]);
				}
				// it1 - from, it2 - to
				it = it1;
				while (it != it2 && it != m_Peers.end ())
				{
					if (ts > it->second->lastSelectionTime + PEER_SELECTION_MIN_INTERVAL &&
					    filter (it->second))
					{
						ident = it->first;
						it->second->lastSelectionTime = ts;
						found = true;
						break;
					}
					it++;
				}
				if (!found)
				{
					// still not found, try from the beginning
					it = m_Peers.begin ();