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23da23a534
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>
96 lines
2.8 KiB
C
96 lines
2.8 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include "gas.h"
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#include "pref.h"
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#include <stdio.h>
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#include <string.h>
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/* Perform isobaric counterdiffusion calculations for gas changes in trimix dives.
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* Here we use the rule-of-fifths where, during a change involving trimix gas, the increase in nitrogen
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* should not exceed one fifth of the decrease in helium.
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* Parameters: 1) pointers to two gas mixes, the gas being switched from and the gas being switched to.
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* 2) a pointer to an icd_data structure.
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* Output: i) The icd_data stucture is filled with the delta_N2 and delta_He numbers (as permille).
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* ii) Function returns a boolean indicating an exceeding of the rule-of-fifths. False = no icd problem.
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*/
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bool isobaric_counterdiffusion(struct gasmix oldgasmix, struct gasmix newgasmix, struct icd_data *results)
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{
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if (!prefs.show_icd)
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return false;
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results->dN2 = get_he(oldgasmix) + get_o2(oldgasmix) - get_he(newgasmix) - get_o2(newgasmix);
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results->dHe = get_he(newgasmix) - get_he(oldgasmix);
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return get_he(oldgasmix) > 0 && results->dN2 > 0 && results->dHe < 0 && get_he(oldgasmix) && results->dN2 > 0 && 5 * results->dN2 > -results->dHe;
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}
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static bool gasmix_is_invalid(struct gasmix mix)
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{
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return mix.o2.permille < 0;
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}
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int same_gasmix(struct gasmix a, struct gasmix b)
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{
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if (gasmix_is_invalid(a) || gasmix_is_invalid(b))
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return 0;
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if (gasmix_is_air(a) && gasmix_is_air(b))
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return 1;
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return a.o2.permille == b.o2.permille && a.he.permille == b.he.permille;
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}
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void sanitize_gasmix(struct gasmix *mix)
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{
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unsigned int o2, he;
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o2 = mix->o2.permille;
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he = mix->he.permille;
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/* Regular air: leave empty */
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if (!he) {
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if (!o2)
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return;
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/* 20.8% to 21% O2 is just air */
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if (gasmix_is_air(*mix)) {
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mix->o2.permille = 0;
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return;
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}
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}
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/* Sane mix? */
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if (o2 <= 1000 && he <= 1000 && o2 + he <= 1000)
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return;
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fprintf(stderr, "Odd gasmix: %u O2 %u He\n", o2, he);
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memset(mix, 0, sizeof(*mix));
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}
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int gasmix_distance(struct gasmix a, struct gasmix b)
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{
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int a_o2 = get_o2(a), b_o2 = get_o2(b);
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int a_he = get_he(a), b_he = get_he(b);
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int delta_o2 = a_o2 - b_o2, delta_he = a_he - b_he;
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delta_he = delta_he * delta_he;
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delta_o2 = delta_o2 * delta_o2;
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return delta_he + delta_o2;
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}
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bool gasmix_is_air(struct gasmix gasmix)
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{
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int o2 = gasmix.o2.permille;
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int he = gasmix.he.permille;
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return (he == 0) && (o2 == 0 || ((o2 >= O2_IN_AIR - 1) && (o2 <= O2_IN_AIR + 1)));
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}
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static fraction_t make_fraction(int i)
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{
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fraction_t res;
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res.permille = i;
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return res;
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}
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fraction_t get_gas_component_fraction(struct gasmix mix, enum gas_component component)
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{
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switch (component) {
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case O2: return make_fraction(get_o2(mix));
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case N2: return make_fraction(get_n2(mix));
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case HE: return make_fraction(get_he(mix));
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default: return make_fraction(0);
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}
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}
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