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80 lines
2.4 KiB
C
80 lines
2.4 KiB
C
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// 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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