Add function to calculate gas maximum narcotic depth

Signed-off-by: Rick Walsh <rickmwalsh@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

6 files changed, 20 insertions, 9 deletions

diff --git a/core/dive.c b/core/dive.c
index 29198afd6..9db233dca 100644
--- a/core/dive.c
+++ b/core/dive.c
@@ -3661,7 +3661,7 @@ fraction_t best_He(depth_t depth, struct dive *dive)
 {
 	fraction_t fhe;
 	int pnarcotic, ambient;
-	pnarcotic = depth_to_mbar(prefs.bestmixend, dive);
+	pnarcotic = depth_to_mbar(prefs.bestmixend.mm, dive);
 	ambient = depth_to_mbar(depth.mm, dive);
 	fhe.permille = (100 - 100 * pnarcotic / ambient) * 10;	//use integer arithmetic to round up to nearest percent
 	if (fhe.permille < 0)
diff --git a/core/dive.h b/core/dive.h
index 9c612048d..c968746f8 100644
--- a/core/dive.h
+++ b/core/dive.h
@@ -481,6 +481,17 @@ static inline depth_t gas_mod(struct gasmix *mix, pressure_t po2_limit, struct d
 	return rounded_depth;
 }
 
+/* Maximum narcotic depth rounded to multiples of roundto mm */
+static inline depth_t gas_mnd(struct gasmix *mix, depth_t end, struct dive *dive, int roundto) {
+	depth_t rounded_depth;
+	pressure_t ppo2n2;
+	ppo2n2.mbar = depth_to_mbar(end.mm, dive);
+
+	double maxambient = ppo2n2.mbar / (1 - get_he(mix) / 1000.0);
+	rounded_depth.mm = rint(mbar_to_depth(maxambient, dive) / roundto) * roundto;
+	return rounded_depth;
+}
+
 #define SURFACE_THRESHOLD 750 /* somewhat arbitrary: only below 75cm is it really diving */
 
 /* this is a global spot for a temporary dive structure that we use to
diff --git a/core/pref.h b/core/pref.h
index a0f9158b8..a30417923 100644
--- a/core/pref.h
+++ b/core/pref.h
@@ -92,7 +92,7 @@ struct preferences {
 	int descrate;
 	int bottompo2;
 	int decopo2;
-	int bestmixend;
+	depth_t bestmixend;
 	int proxy_type;
 	char *proxy_host;
 	int proxy_port;
diff --git a/core/subsurface-qt/SettingsObjectWrapper.cpp b/core/subsurface-qt/SettingsObjectWrapper.cpp
index b8865e256..4604abfd7 100644
--- a/core/subsurface-qt/SettingsObjectWrapper.cpp
+++ b/core/subsurface-qt/SettingsObjectWrapper.cpp
@@ -917,7 +917,7 @@ int DivePlannerSettings::decopo2() const
 
 int DivePlannerSettings::bestmixend() const
 {
-	return prefs.bestmixend;
+	return prefs.bestmixend.mm;
 }
 
 int DivePlannerSettings::reserveGas() const
@@ -1099,7 +1099,7 @@ void DivePlannerSettings::setBestmixend(int value)
 	QSettings s;
 	s.beginGroup(group);
 	s.setValue("bestmixend", value);
-	prefs.bestmixend = value;
+	prefs.bestmixend.mm = value;
 	emit bestmixendChanged(value);
 }
 
diff --git a/core/subsurfacestartup.c b/core/subsurfacestartup.c
index 1dba381de..126cc5ee1 100644
--- a/core/subsurfacestartup.c
+++ b/core/subsurfacestartup.c
@@ -52,7 +52,7 @@ struct preferences default_prefs = {
 	.descrate = 18000 / 60,
 	.bottompo2 = 1400,
 	.decopo2 = 1600,
-	.bestmixend = 30000,
+	.bestmixend.mm = 30000,
 	.doo2breaks = false,
 	.drop_stone_mode = false,
 	.switch_at_req_stop = false,
diff --git a/desktop-widgets/diveplanner.cpp b/desktop-widgets/diveplanner.cpp
index 7ac88f9bc..31dd4bb93 100644
--- a/desktop-widgets/diveplanner.cpp
+++ b/desktop-widgets/diveplanner.cpp
@@ -291,7 +291,7 @@ PlannerSettingsWidget::PlannerSettingsWidget(QWidget *parent, Qt::WindowFlags f)
 	prefs.descrate = s.value("descrate", prefs.descrate).toInt();
 	prefs.bottompo2 = s.value("bottompo2", prefs.bottompo2).toInt();
 	prefs.decopo2 = s.value("decopo2", prefs.decopo2).toInt();
-	prefs.bestmixend = s.value("bestmixend", prefs.bestmixend).toInt();
+	prefs.bestmixend.mm = s.value("bestmixend", prefs.bestmixend.mm).toInt();
 	prefs.doo2breaks = s.value("doo2breaks", prefs.doo2breaks).toBool();
 	prefs.switch_at_req_stop = s.value("switch_at_req_stop", prefs.switch_at_req_stop).toBool();
 	prefs.min_switch_duration = s.value("min_switch_duration", prefs.min_switch_duration).toInt();
@@ -385,7 +385,7 @@ void PlannerSettingsWidget::updateUnitsUI()
 	ui.ascRateStops->setValue(rint(prefs.ascratestops / UNIT_FACTOR));
 	ui.ascRateLast6m->setValue(rint(prefs.ascratelast6m / UNIT_FACTOR));
 	ui.descRate->setValue(rint(prefs.descrate / UNIT_FACTOR));
-	ui.bestmixEND->setValue(rint(get_depth_units(prefs.bestmixend, NULL, NULL)));
+	ui.bestmixEND->setValue(rint(get_depth_units(prefs.bestmixend.mm, NULL, NULL)));
 }
 
 PlannerSettingsWidget::~PlannerSettingsWidget()
@@ -406,7 +406,7 @@ PlannerSettingsWidget::~PlannerSettingsWidget()
 	s.setValue("descrate", prefs.descrate);
 	s.setValue("bottompo2", prefs.bottompo2);
 	s.setValue("decopo2", prefs.decopo2);
-	s.setValue("bestmixend", prefs.bestmixend);
+	s.setValue("bestmixend", prefs.bestmixend.mm);
 	s.setValue("doo2breaks", prefs.doo2breaks);
 	s.setValue("drop_stone_mode", prefs.drop_stone_mode);
 	s.setValue("switch_at_req_stop", prefs.switch_at_req_stop);
@@ -522,7 +522,7 @@ void PlannerSettingsWidget::setDecoPo2(double po2)
 
 void PlannerSettingsWidget::setBestmixEND(int depth)
 {
-	prefs.bestmixend = units_to_depth(depth);
+	prefs.bestmixend.mm = units_to_depth(depth);
 }
 
 void PlannerSettingsWidget::setBackgasBreaks(bool dobreaks)