Speed up resolving a fixed number of streams

Previously, the completion criterion was check with each resolve wave
(i.e. all 0.5 seconds), even if all needed streams had already been found.
This commit checks whenever a new stream is found so stream resolution
can finish as soon as all stream are found.

Author: tstenner

src/resolve_attempt_udp.cpp

@@ -136,6 +136,10 @@ void resolve_attempt_udp::handle_receive_outcome(err_t err, std::size_t len) {
 							stored_info.v6address(remote_endpoint_.address().to_string());
 					}
 				}
+				// prepone the next cancellation check, i.e. when all needed streams are found,
+				// cancel immediately rather than when a wave timer is due half a second later
+				if (resolver_.check_cancellation_criteria())
+					resolver_.cancel_ongoing_resolve();
 			}
 		} catch (std::exception &e) {
 			LOG_F(WARNING, "resolve_attempt_udp: hiccup while processing the received data: %s",

src/resolver_impl.cpp

@@ -170,13 +170,7 @@ std::vector<stream_info_impl> resolver_impl::results(uint32_t max_results) {
 // === timer-driven async handlers ===
 
 void resolver_impl::next_resolve_wave() {
-	std::size_t num_results = 0;
-	{
-		std::lock_guard<std::mutex> lock(results_mut_);
-		num_results = results_.size();
-	}
-	if (cancelled_ || expired_ ||
-		(minimum_ && (num_results >= (std::size_t)minimum_) && lsl_clock() >= wait_until_)) {
+	if (check_cancellation_criteria()) {
 		// stopping criteria satisfied: cancel the ongoing operations
 		cancel_ongoing_resolve();
 	} else {
@@ -244,6 +238,19 @@ void resolver_impl::cancel() {
 	cancel_ongoing_resolve();
 }
 
+bool resolver_impl::check_cancellation_criteria()
+{
+	std::size_t num_results = 0;
+	{
+		std::lock_guard<std::mutex> lock(results_mut_);
+		num_results = results_.size();
+	}
+	if (cancelled_ || expired_) return true;
+	if (minimum_ && (num_results >= (std::size_t)minimum_) && lsl_clock() >= wait_until_)
+		return true;
+	return false;
+}
+
 void resolver_impl::cancel_ongoing_resolve() {
 	// make sure that ongoing handler loops terminate
 	expired_ = true;

src/resolver_impl.h

@@ -140,6 +140,9 @@ class resolver_impl : public cancellable_registry {
 	/// Start a new resolver attempt on the known peers.
 	void udp_unicast_burst(err_t err);
 
+	/// Check if cancellation criteria (minimum number of results, timeout) are met
+	bool check_cancellation_criteria();
+
 	/// Cancel the currently ongoing resolve, if any.
 	void cancel_ongoing_resolve();