core: add cast_int<> function

We had a pattern where doubles were converted to long with
lrint() and then down-cast to a narrower int type.

Because this is unwieldy, introduce a function encapsulating
this.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

core/dive.cpp

@@ -554,7 +554,7 @@ static void match_standard_cylinder(cylinder_type_t &type)
 	default:
 		return;
 	}
-	type.description = format_string_std(fmt, (int)lrint(cuft));
+	type.description = format_string_std(fmt, int_cast<int>(cuft));
 }
 
 /*
@@ -2439,7 +2439,7 @@ int dive::rel_mbar_to_depth(int mbar) const
 
 	/* whole mbar gives us cm precision */
 	double specific_weight = salinity_to_specific_weight(salinity);
-	return (int)lrint(mbar / specific_weight);
+	return int_cast<int>(mbar / specific_weight);
 }
 
 int dive::mbar_to_depth(int mbar) const
@@ -2459,7 +2459,7 @@ int dive::mbar_to_depth(int mbar) const
 depth_t dive::gas_mod(struct gasmix mix, pressure_t po2_limit, int roundto) const
 {
 	double depth = (double) mbar_to_depth(po2_limit.mbar * 1000 / get_o2(mix));
-	return depth_t { .mm = (int)lrint(depth / roundto) * roundto };
+	return depth_t { .mm = int_cast<int>(depth / roundto) * roundto };
 }
 
 /* Maximum narcotic depth rounded to multiples of roundto mm */
@@ -2468,14 +2468,14 @@ depth_t dive::gas_mnd(struct gasmix mix, depth_t end, int roundto) const
 	pressure_t ppo2n2 { .mbar = depth_to_mbar(end.mm) };
 
 	int maxambient = prefs.o2narcotic ?
-					(int)lrint(ppo2n2.mbar / (1 - get_he(mix) / 1000.0))
+					int_cast<int>(ppo2n2.mbar / (1 - get_he(mix) / 1000.0))
 			      :
 					get_n2(mix) > 0 ?
-						(int)lrint(ppo2n2.mbar * N2_IN_AIR / get_n2(mix))
+						int_cast<int>(ppo2n2.mbar * N2_IN_AIR / get_n2(mix))
 					:
 						// Actually: Infinity
 						1000000;
-	return depth_t { .mm = (int)lrint(((double)mbar_to_depth(maxambient)) / roundto) * roundto };
+	return depth_t { .mm = int_cast<int>(((double)mbar_to_depth(maxambient)) / roundto) * roundto };
 }
 
 std::string dive::get_country() const

core/equipment.cpp

@@ -182,7 +182,7 @@ volume_t cylinder_t::gas_volume(pressure_t p) const
 {
 	double bar = p.mbar / 1000.0;
 	double z_factor = gas_compressibility_factor(gasmix, bar);
-	return volume_t { .mliter = static_cast<int>(lrint(type.size.mliter * bar_to_atm(bar) / z_factor)) };
+	return volume_t { .mliter = int_cast<int>(type.size.mliter * bar_to_atm(bar) / z_factor) };
 }
 
 int find_best_gasmix_match(struct gasmix mix, const struct cylinder_table &cylinders)
@@ -348,7 +348,7 @@ void copy_cylinder_types(const struct dive *s, struct dive *d)
 void fill_default_cylinder(const struct dive *dive, cylinder_t *cyl)
 {
 	const std::string &cyl_name = prefs.default_cylinder;
-	pressure_t pO2 = {.mbar = static_cast<int>(lrint(prefs.modpO2 * 1000.0))};
+	pressure_t pO2 = {.mbar = int_cast<int>(prefs.modpO2 * 1000.0)};
 
 	if (cyl_name.empty())
 		return;

core/filterconstraint.cpp

@@ -283,7 +283,7 @@ static int display_to_base_unit(double f, enum filter_constraint_type type)
 	switch (desc->units) {
 	case FILTER_CONSTRAINT_NO_UNIT:
 	default:
-		return (int)lrint(f);
+		return int_cast<int>(f);
 	case FILTER_CONSTRAINT_LENGTH_UNIT:
 		return prefs.units.length == units::METERS ? lrint(f * 1000.0) : feet_to_mm(f);
 	case FILTER_CONSTRAINT_DURATION_UNIT:

core/load-git.cpp

@@ -93,17 +93,17 @@ static weight_t get_weight(const char *line)
 
 static pressure_t get_airpressure(const char *line)
 {
-	return pressure_t { .mbar = static_cast<int32_t>(lrint(ascii_strtod(line, NULL))) };
+	return pressure_t { .mbar = int_cast<int32_t>(ascii_strtod(line, NULL)) };
 }
 
 static pressure_t get_pressure(const char *line)
 {
-	return pressure_t { .mbar = static_cast<int32_t>(lrint(1000 * ascii_strtod(line, NULL))) };
+	return pressure_t { .mbar = int_cast<int32_t>(1000 * ascii_strtod(line, NULL)) };
 }
 
 static o2pressure_t get_o2pressure(const char *line)
 {
-	return o2pressure_t { .mbar = static_cast<uint16_t>(lrint(1000 * ascii_strtod(line, NULL))) };
+	return o2pressure_t { .mbar = int_cast<uint16_t>(1000 * ascii_strtod(line, NULL)) };
 }
 
 static int get_salinity(const char *line)

core/statistics.cpp

@@ -275,8 +275,8 @@ static std::pair<volume_t, volume_t> get_gas_parts(struct gasmix mix, volume_t v
 	if (gasmix_is_air(mix))
 		return { volume_t() , volume_t() };
 
-	volume_t air { .mliter = (int)lrint(((double)vol.mliter * get_n2(mix)) / (1000 - o2_in_topup)) };
-	volume_t he { .mliter = (int)lrint(((double)vol.mliter * get_he(mix)) / 1000.0) };
+	volume_t air { .mliter = int_cast<int>(((double)vol.mliter * get_n2(mix)) / (1000 - o2_in_topup)) };
+	volume_t he { .mliter = int_cast<int>(((double)vol.mliter * get_he(mix)) / 1000.0) };
 	volume_t o2 { .mliter = vol.mliter - he.mliter - air.mliter };
 	return std::make_pair(o2, he);
 }

core/units.cpp

@@ -22,7 +22,7 @@ int get_pressure_units(int mb, const char **units)
 		unit = translate("gettextFromC", "bar");
 		break;
 	case units::PSI:
-		pressure = (int)lrint(mbar_to_PSI(mb));
+		pressure = int_cast<int>(mbar_to_PSI(mb));
 		unit = translate("gettextFromC", "psi");
 		break;
 	}

core/units.h

@@ -67,6 +67,17 @@
  */
 using timestamp_t = int64_t;
 
+/*
+ * There is a semi-common pattern where lrint() is used to round
+ * doubles to long integers and then cast down to a less wide
+ * int. Since this is unwieldy, encapsulate this in this function
+ */
+template <typename INT>
+INT int_cast(double v)
+{
+	return static_cast<INT>(lrint(v));
+}
+
 // Base class for all unit types using the "Curiously recurring template pattern"
 // (https://en.wikipedia.org/wiki/Curiously_recurring_template_pattern)
 // to implement addition, subtraction and negation.
@@ -190,8 +201,8 @@ static inline bool operator!=(const location_t &a, const location_t &b)
 static inline location_t create_location(double lat, double lon)
 {
 	location_t location = {
-		{ .udeg = (int) lrint(lat * 1000000) },
-		{ .udeg = (int) lrint(lon * 1000000) }
+		{ .udeg = int_cast<int>(lat * 1000000) },
+		{ .udeg = int_cast<int>(lon * 1000000) }
 	};
 	return location;
 }
@@ -208,7 +219,7 @@ static inline double grams_to_lbs(int grams)
 
 static inline int lbs_to_grams(double lbs)
 {
-	return (int)lrint(lbs * 453.6);
+	return int_cast<int>(lbs * 453.6);
 }
 
 static inline double ml_to_cuft(int ml)
@@ -238,7 +249,7 @@ static inline long feet_to_mm(double feet)
 
 static inline int to_feet(depth_t depth)
 {
-	return (int)lrint(mm_to_feet(depth.mm));
+	return int_cast<int>(mm_to_feet(depth.mm));
 }
 
 static inline double mkelvin_to_C(int mkelvin)

mobile-widgets/qmlmanager.cpp

@@ -1170,13 +1170,13 @@ static weight_t parseWeight(const QString &text)
 		return {};
 	double number = numOnly.toDouble();
 	if (text.contains(gettextFromC::tr("kg"), Qt::CaseInsensitive)) {
-		return { .grams = static_cast<int>(lrint(number * 1000)) };
+		return { .grams = int_cast<int>(number * 1000) };
 	} else if (text.contains(gettextFromC::tr("lbs"), Qt::CaseInsensitive)) {
 		return { .grams = lbs_to_grams(number) };
 	} else {
 		switch (prefs.units.weight) {
 		case units::KG:
-			return { .grams = static_cast<int>(lrint(number * 1000)) };
+			return { .grams = int_cast<int>(number * 1000) };
 		case units::LBS:
 			return { .grams = lbs_to_grams(number) };
 		default:

qt-models/diveplannermodel.cpp

@@ -296,7 +296,7 @@ QVariant DivePlannerPointsModel::data(const QModelIndex &index, int role) const
 		case CCSETPOINT:
 			return (divemode == CCR) ? (double)(p.setpoint / 1000.0) : QVariant();
 		case DEPTH:
-			return (int) lrint(get_depth_units(p.depth.mm, NULL, NULL));
+			return int_cast<int>(get_depth_units(p.depth.mm, NULL, NULL));
 		case RUNTIME:
 			return p.time / 60;
 		case DURATION:

smtk-import/smartrak.cpp

@@ -1001,7 +1001,7 @@ void smartrak_import(const char *file, struct divelog *log)
 
 		/* No DC related data */
 		smtkdive->visibility = strtod((char *)col[coln(VISIBILITY)]->bind_ptr, NULL) > 25 ? 5 : lrint(strtod((char *)col[13]->bind_ptr, NULL) / 5);
-		weightsystem_t ws = { { .grams = (int)lrint(strtod((char *)col[coln(WEIGHT)]->bind_ptr, NULL) * 1000)}, std::string(), false };
+		weightsystem_t ws = { { .grams = int_cast<int>(strtod((char *)col[coln(WEIGHT)]->bind_ptr, NULL) * 1000)}, std::string(), false };
 		smtkdive->weightsystems.push_back(std::move(ws));
 		smtkdive->suit = get(suit_list, atoi((char *)col[coln(SUITIDX)]->bind_ptr) - 1);
 		smtk_build_location(mdb_clon, (char *)col[coln(SITEIDX)]->bind_ptr, &smtkdive->dive_site, log);