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core: add N2 and general gas component accessors

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There were helper functions to access O2 and He component fractions.
Add another one for N2. Indeed, this can be used in three cases, where
N2 was deduced indirectly.

Moreover, add a general accessor with a gas_component argument.
This will be used by the filter code to filter for gas components.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
This commit is contained in:
Berthold Stoeger 2020-10-02 19:58:36 +02:00 • committed by Dirk Hohndel
parent 34730b898b
commit 23da23a534
3 changed files with 26 additions and 3 deletions
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6
core/dive.c
View file

@ -2065,7 +2065,7 @@ void fill_pressures(struct gas_pressures *pressures, const double amb_pressure,
pressures->o2 = 0;
if (get_o2(mix) != 1000) {
pressures->he = (amb_pressure - pressures->o2) * get_he(mix) / (1000.0 - get_o2(mix));
pressures->n2 = (amb_pressure - pressures->o2) * (1000 - get_o2(mix) - get_he(mix)) / (1000.0 - get_o2(mix));
pressures->n2 = (amb_pressure - pressures->o2) * get_n2(mix) / (1000.0 - get_o2(mix));
} else {
pressures->he = pressures->n2 = 0;
}
@ -2073,7 +2073,7 @@ void fill_pressures(struct gas_pressures *pressures, const double amb_pressure,
// Open circuit dives: no gas pressure values available, they need to be calculated
pressures->o2 = get_o2(mix) / 1000.0 * amb_pressure; // These calculations are also used if the CCR calculation above..
pressures->he = get_he(mix) / 1000.0 * amb_pressure; // ..returned a po2 of zero (i.e. o2 sensor data not resolvable)
pressures->n2 = (1000 - get_o2(mix) - get_he(mix)) / 1000.0 * amb_pressure;
pressures->n2 = get_n2(mix) / 1000.0 * amb_pressure;
}
}
}
@ -3760,7 +3760,7 @@ depth_t gas_mnd(struct gasmix mix, depth_t end, const struct dive *dive, int rou
int maxambient = prefs.o2narcotic ?
(int)lrint(ppo2n2.mbar / (1 - get_he(mix) / 1000.0))
:
(int)lrint(ppo2n2.mbar * N2_IN_AIR / (1000 - get_he(mix) - get_o2(mix)));
(int)lrint(ppo2n2.mbar * N2_IN_AIR / get_n2(mix));
rounded_depth.mm = (int)lrint(((double)mbar_to_depth(maxambient, dive)) / roundto) * roundto;
return rounded_depth;
}

17
core/gas.c
View file

@ -77,3 +77,20 @@ bool gasmix_is_air(struct gasmix gasmix)
int he = gasmix.he.permille;
return (he == 0) && (o2 == 0 || ((o2 >= O2_IN_AIR - 1) && (o2 <= O2_IN_AIR + 1)));
}
static fraction_t make_fraction(int i)
{
fraction_t res;
res.permille = i;
return res;
}
fraction_t get_gas_component_fraction(struct gasmix mix, enum gas_component component)
{
switch (component) {
case O2: return make_fraction(get_o2(mix));
case N2: return make_fraction(get_n2(mix));
case HE: return make_fraction(get_he(mix));
default: return make_fraction(0);
}
}

6
core/gas.h
View file

@ -43,12 +43,18 @@ static inline int get_he(struct gasmix mix)
return mix.he.permille;
}
static inline int get_n2(struct gasmix mix)
{
return 1000 - get_o2(mix) - get_he(mix);
}
struct gas_pressures {
double o2, n2, he;
};
extern void sanitize_gasmix(struct gasmix *mix);
extern int gasmix_distance(struct gasmix a, struct gasmix b);
extern fraction_t get_gas_component_fraction(struct gasmix mix, enum gas_component component);
extern bool gasmix_is_air(struct gasmix gasmix);