Don't access gasmix.o2.fraction

Air is a special gas that does not contain oxygen according
to gasmix.o2.fraction. If you want to use the fo2, you
need to use get_o2() to treat this special case correctly.

This fixes a bug when setting the MND of a gas containing
21% oxygen when o2 is considered not narcotic.

Reported-by: Christoph Gruen <gruen.christoph@gmail.com>
Signed-off-by: Robert C. Helling <helling@atdotde.de>

3 files changed, 17 insertions, 14 deletions

diff --git a/core/gas-model.c b/core/gas-model.c
index 44c64864a..115da0356 100644
--- a/core/gas-model.c
+++ b/core/gas-model.c
@@ -86,7 +86,9 @@ double isothermal_pressure(struct gasmix gas, double p1, int volume1, int volume
 
 double gas_density(struct gasmix gas, int pressure)
 {
-	int density =  gas.he.permille * HE_DENSITY + gas.o2.permille * O2_DENSITY + (1000 - gas.he.permille - gas.o2.permille) * N2_DENSITY;
+	int fo2 = get_o2(gas);
+	int fhe = get_he(gas);
+	int density =  fhe * HE_DENSITY + fo2 * O2_DENSITY + (1000 - fhe - fo2) * N2_DENSITY;
 
 	return density * (double) pressure / gas_compressibility_factor(gas, pressure / 1000.0) / SURFACE_PRESSURE / 1000000.0;
 }
diff --git a/core/gas.c b/core/gas.c
index 8dbfe61cb..1e74dccfc 100644
--- a/core/gas.c
+++ b/core/gas.c
@@ -33,15 +33,15 @@ int same_gasmix(struct gasmix a, struct gasmix b)
 		return 0;
 	if (gasmix_is_air(a) && gasmix_is_air(b))
 		return 1;
-	return a.o2.permille == b.o2.permille && a.he.permille == b.he.permille;
+	return get_o2(a) == get_o2(b) && get_he(a) == get_he(b);
 }
 
 void sanitize_gasmix(struct gasmix *mix)
 {
 	unsigned int o2, he;
 
-	o2 = mix->o2.permille;
-	he = mix->he.permille;
+	o2 = get_o2(*mix);
+	he = get_he(*mix);
 
 	/* Regular air: leave empty */
 	if (!he) {
@@ -74,12 +74,12 @@ int gasmix_distance(struct gasmix a, struct gasmix b)
 
 bool gasmix_is_air(struct gasmix gasmix)
 {
-	int o2 = gasmix.o2.permille;
-	int he = gasmix.he.permille;
+	int o2 = get_o2(gasmix);
+	int he = get_he(gasmix);
 	return (he == 0) && (o2 == 0 || ((o2 >= O2_IN_AIR - 1) && (o2 <= O2_IN_AIR + 1)));
 }
 
-static fraction_t make_fraction(int i)
+fraction_t make_fraction(int i)
 {
 	fraction_t res;
 	res.permille = i;
@@ -152,13 +152,13 @@ enum gastype gasmix_to_type(struct gasmix mix)
 {
 	if (gasmix_is_air(mix))
 		return GASTYPE_AIR;
-	if (mix.o2.permille >= 980)
+	if (get_o2(mix) >= 980)
 		return GASTYPE_OXYGEN;
-	if (mix.he.permille == 0)
-		return mix.o2.permille >= 230 ? GASTYPE_NITROX : GASTYPE_AIR;
-	if (mix.o2.permille <= 180)
+	if (get_he(mix) == 0)
+		return get_o2(mix) >= 230 ? GASTYPE_NITROX : GASTYPE_AIR;
+	if (get_o2(mix) <= 180)
 		return GASTYPE_HYPOXIC_TRIMIX;
-	return mix.o2.permille <= 230 ? GASTYPE_NORMOXIC_TRIMIX : GASTYPE_HYPEROXIC_TRIMIX;
+	return get_o2(mix) <= 230 ? GASTYPE_NORMOXIC_TRIMIX : GASTYPE_HYPEROXIC_TRIMIX;
 }
 
 static const char *gastype_names[] = {
diff --git a/core/gas.h b/core/gas.h
index 83eef72e9..b3c539c61 100644
--- a/core/gas.h
+++ b/core/gas.h
@@ -44,12 +44,12 @@ extern double isothermal_pressure(struct gasmix gas, double p1, int volume1, int
 extern double gas_density(struct gasmix gas, int pressure);
 extern int same_gasmix(struct gasmix a, struct gasmix b);
 
-static inline int get_o2(struct gasmix mix)
+static inline int get_o2(const struct gasmix mix)
 {
 	return mix.o2.permille ?: O2_IN_AIR;
 }
 
-static inline int get_he(struct gasmix mix)
+static inline int get_he(const struct gasmix mix)
 {
 	return mix.he.permille;
 }
@@ -74,6 +74,7 @@ extern bool gasmix_is_air(struct gasmix gasmix);
 extern bool gasmix_is_invalid(struct gasmix mix);
 extern enum gastype gasmix_to_type(struct gasmix mix);
 extern const char *gastype_name(enum gastype type);
+extern fraction_t make_fraction(int f);
 
 #ifdef __cplusplus
 }