Refactor input port monitoring

* avoid memory allocation (remove std:set<>&)
* skip nested loop using port-names as IDs

However this adds a bit of extra cost in case input ports are
monitored: get_port_by_name() and get_buffer()

libs/ardour/ardour/monitor_port.h

@@ -19,6 +19,7 @@
 #ifndef _ardour_monitor_port_h_
 #define _ardour_monitor_port_h_
 
+#include <boost/shared_ptr.hpp>
 #include <set>
 
 #include "zita-resampler/vmresampler.h"
@@ -26,6 +27,7 @@
 #include "pbd/rcu.h"
 
 #include "ardour/audio_buffer.h"
+#include "ardour/port_engine.h"
 
 namespace ARDOUR {
 
@@ -50,10 +52,7 @@ public:
 protected:
 	friend class PortManager;
 	MonitorPort ();
-
-	void prepare (std::set<std::string>&);
-	void monitor (Sample*, pframes_t, std::string const&);
-	void finalize (pframes_t);
+	void monitor (PortEngine&, pframes_t);
 
 private:
 	struct MonitorInfo {
@@ -67,10 +66,11 @@ private:
 		bool  remove;
 	};
 
-	typedef std::map<std::string, boost::shared_ptr<MonitorInfo> > MonitorPorts;
+	void collect (boost::shared_ptr<MonitorInfo>, Sample*, pframes_t, std::string const&);
+	void finalize (pframes_t);
 
+	typedef std::map<std::string, boost::shared_ptr<MonitorInfo> > MonitorPorts;
 	SerializedRCUManager<MonitorPorts> _monitor_ports;
-	boost::shared_ptr<MonitorPorts>    _cycle_ports;
 
 	AudioBuffer*            _buffer;
 	ArdourZita::VMResampler _src;

libs/ardour/monitor_port.cc

@@ -78,28 +78,37 @@ MonitorPort::silent () const
 }
 
 void
-MonitorPort::prepare (std::set<std::string>& portset)
+MonitorPort::monitor (PortEngine& e, pframes_t n_samples)
 {
 	if (!_silent) {
 		memset (_input, 0, sizeof (Sample) * _insize);
 		_silent = true;
 	}
+	boost::shared_ptr<MonitorPorts> cycle_ports = _monitor_ports.reader ();
 
-	_cycle_ports = _monitor_ports.reader ();
-	for (MonitorPorts::iterator i = _cycle_ports->begin (); i != _cycle_ports->end(); ++i) {
+	for (MonitorPorts::iterator i = cycle_ports->begin (); i != cycle_ports->end(); ++i) {
 		if (i->second->remove && i->second->gain == 0) {
 			continue;
 		}
-		portset.insert (i->first);
+
+		PortEngine::PortHandle ph = e.get_port_by_name (i->first);
+		if (!ph) {
+			continue;
+		}
+		Sample* buf = (Sample*) e.get_buffer (ph, n_samples);
+		if (!buf) {
+			continue;
+		}
+		collect (i->second, buf, n_samples, i->first);
 	}
+	finalize (n_samples);
 }
 
 void
-MonitorPort::monitor (Sample* buf, pframes_t n_samples, std::string const& pn)
+MonitorPort::collect (boost::shared_ptr<MonitorInfo> mi, Sample* buf, pframes_t n_samples, std::string const& pn)
 {
-	MonitorPorts::iterator i = _cycle_ports->find (pn);
-	gain_t target_gain = i->second->remove ? 0.0 : 1.0;
-	gain_t current_gain = i->second->gain;
+	gain_t target_gain = mi->remove ? 0.0 : 1.0;
+	gain_t current_gain = mi->gain;
 
 	if (target_gain == current_gain && target_gain == 0) {
 		return;
@@ -129,7 +138,7 @@ MonitorPort::monitor (Sample* buf, pframes_t n_samples, std::string const& pn)
 			offset += n_proc;
 		}
 		if (fabsf (current_gain - target_gain) < GAIN_COEFF_DELTA) {
-			i->second->gain = target_gain;
+			mi->gain = target_gain;
 #if 1 // not strictly needed
 			if (target_gain == 0) {
 				/* remove port from list, uses RCUWriter */
@@ -137,7 +146,7 @@ MonitorPort::monitor (Sample* buf, pframes_t n_samples, std::string const& pn)
 			}
 #endif
 		} else {
-			i->second->gain = current_gain;
+			mi->gain = current_gain;
 		}
 	}
 	_silent = false;
@@ -158,7 +167,6 @@ MonitorPort::finalize (pframes_t n_samples)
 		++_src.out_data;
 		--_src.out_count;
 	}
-	_cycle_ports.reset ();
 }
 
 ARDOUR::AudioBuffer&

libs/ardour/port_manager.cc

@@ -1765,8 +1765,7 @@ PortManager::run_input_meters (pframes_t n_samples, samplecnt_t rate)
 
 	const float falloff = falloff_cache.calc (n_samples, rate);
 
-	std::set<std::string> monitor_portset;
-	_monitor_port.prepare (monitor_portset);
+	_monitor_port.monitor (port_engine (), n_samples);
 
 	/* calculate peak of all physical inputs (readable ports) */
 	std::vector<std::string> port_names;
@@ -1799,9 +1798,6 @@ PortManager::run_input_meters (pframes_t n_samples, samplecnt_t rate)
 			continue;
 		}
 
-		if (monitor_portset.find (*p) != monitor_portset.end ()) {
-			_monitor_port.monitor (buf, n_samples, *p);
-		}
 
 		ai->second.scope->write (buf, n_samples);
 
@@ -1818,8 +1814,6 @@ PortManager::run_input_meters (pframes_t n_samples, samplecnt_t rate)
 		ai->second.meter->peak  = std::max (ai->second.meter->peak, level);
 	}
 
-	_monitor_port.finalize (n_samples);
-
 	/* MIDI */
 	port_names.clear ();
 	get_physical_inputs (DataType::MIDI, port_names);