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794066b236
Instead of accessing the cylinder table directly, use the get_cylinder() function. This gives less unwieldy expressions. But more importantly, the function does bound checking. This is crucial for now as the code hasn't be properly audited since the change to arbitrarily sized cylinder tables. Accesses of invalid cylinder indexes may lead to silent data-corruption that is sometimes not even noticed by valgrind. Returning NULL instead of an invalid pointer will make debugging much easier. Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
486 lines
15 KiB
C
486 lines
15 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/* gaspressures.c
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* ---------------
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* This file contains the routines to calculate the gas pressures in the cylinders.
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* The functions below support the code in profile.c.
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* The high-level function is populate_pressure_information(), called by function
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* create_plot_info_new() in profile.c. The other functions below are, in turn,
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* called by populate_pressure_information(). The calling sequence is as follows:
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*
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* populate_pressure_information() -> calc_pressure_time()
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* -> fill_missing_tank_pressures() -> fill_missing_segment_pressures()
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* -> get_pr_interpolate_data()
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*
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* The pr_track_t related functions below implement a linked list that is used by
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* the majority of the functions below. The linked list covers a part of the dive profile
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* for which there are no cylinder pressure data. Each element in the linked list
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* represents a segment between two consecutive points on the dive profile.
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* pr_track_t is defined in gaspressures.h
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*/
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#include "ssrf.h"
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#include "dive.h"
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#include "display.h"
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#include "profile.h"
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#include "gaspressures.h"
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#include "pref.h"
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/*
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* simple structure to track the beginning and end tank pressure as
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* well as the integral of depth over time spent while we have no
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* pressure reading from the tank */
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typedef struct pr_track_struct pr_track_t;
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struct pr_track_struct {
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int start;
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int end;
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int t_start;
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int t_end;
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int pressure_time;
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pr_track_t *next;
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};
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typedef struct pr_interpolate_struct pr_interpolate_t;
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struct pr_interpolate_struct {
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int start;
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int end;
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int pressure_time;
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int acc_pressure_time;
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};
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enum interpolation_strategy {SAC, TIME, CONSTANT};
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static pr_track_t *pr_track_alloc(int start, int t_start)
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{
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pr_track_t *pt = malloc(sizeof(pr_track_t));
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pt->start = start;
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pt->end = 0;
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pt->t_start = pt->t_end = t_start;
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pt->pressure_time = 0;
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pt->next = NULL;
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return pt;
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}
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/* poor man's linked list */
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static pr_track_t *list_last(pr_track_t *list)
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{
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pr_track_t *tail = list;
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if (!tail)
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return NULL;
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while (tail->next) {
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tail = tail->next;
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}
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return tail;
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}
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static pr_track_t *list_add(pr_track_t *list, pr_track_t *element)
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{
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pr_track_t *tail = list_last(list);
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if (!tail)
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return element;
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tail->next = element;
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return list;
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}
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static void list_free(pr_track_t *list)
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{
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if (!list)
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return;
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list_free(list->next);
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free(list);
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}
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#ifdef DEBUG_PR_TRACK
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static void dump_pr_track(int cyl, pr_track_t *track_pr)
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{
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pr_track_t *list;
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printf("cyl%d:\n", cyl);
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list = track_pr;
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while (list) {
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printf(" start %d end %d t_start %d:%02d t_end %d:%02d pt %d\n",
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mbar_to_PSI(list->start),
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mbar_to_PSI(list->end),
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FRACTION(list->t_start, 60),
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FRACTION(list->t_end, 60),
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list->pressure_time);
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list = list->next;
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}
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}
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#endif
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/*
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* This looks at the pressures for one cylinder, and
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* calculates any missing beginning/end pressures for
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* each segment by taking the over-all SAC-rate into
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* account for that cylinder.
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*
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* NOTE! Many segments have full pressure information
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* (both beginning and ending pressure). But if we have
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* switched away from a cylinder, we will have the
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* beginning pressure for the first segment with a
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* missing end pressure. We may then have one or more
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* segments without beginning or end pressures, until
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* we finally have a segment with an end pressure.
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*
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* We want to spread out the pressure over these missing
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* segments according to how big of a time_pressure area
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* they have.
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*/
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static void fill_missing_segment_pressures(pr_track_t *list, enum interpolation_strategy strategy)
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{
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double magic;
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while (list) {
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int start = list->start, end;
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pr_track_t *tmp = list;
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int pt_sum = 0, pt = 0;
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for (;;) {
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pt_sum += tmp->pressure_time;
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end = tmp->end;
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if (end)
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break;
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end = start;
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if (!tmp->next)
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break;
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tmp = tmp->next;
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}
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if (!start)
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start = end;
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/*
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* Now 'start' and 'end' contain the pressure values
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* for the set of segments described by 'list'..'tmp'.
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* pt_sum is the sum of all the pressure-times of the
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* segments.
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*
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* Now dole out the pressures relative to pressure-time.
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*/
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list->start = start;
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tmp->end = end;
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switch (strategy) {
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case SAC:
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for (;;) {
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int pressure;
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pt += list->pressure_time;
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pressure = start;
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if (pt_sum)
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pressure -= lrint((start - end) * (double)pt / pt_sum);
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list->end = pressure;
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if (list == tmp)
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break;
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list = list->next;
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list->start = pressure;
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}
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break;
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case TIME:
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if (list->t_end && (tmp->t_start - tmp->t_end)) {
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magic = (list->t_start - tmp->t_end) / (tmp->t_start - tmp->t_end);
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list->end = lrint(start - (start - end) * magic);
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} else {
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list->end = start;
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}
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break;
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case CONSTANT:
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list->end = start;
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}
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/* Ok, we've done that set of segments */
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list = list->next;
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}
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}
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#ifdef DEBUG_PR_INTERPOLATE
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void dump_pr_interpolate(int i, pr_interpolate_t interpolate_pr)
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{
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printf("Interpolate for entry %d: start %d - end %d - pt %d - acc_pt %d\n", i,
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interpolate_pr.start, interpolate_pr.end, interpolate_pr.pressure_time, interpolate_pr.acc_pressure_time);
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}
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#endif
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static struct pr_interpolate_struct get_pr_interpolate_data(pr_track_t *segment, struct plot_info *pi, int cur)
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{ // cur = index to pi->entry corresponding to t_end of segment;
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struct pr_interpolate_struct interpolate;
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int i;
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struct plot_data *entry;
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interpolate.start = segment->start;
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interpolate.end = segment->end;
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interpolate.acc_pressure_time = 0;
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interpolate.pressure_time = 0;
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for (i = 0; i < pi->nr; i++) {
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entry = pi->entry + i;
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if (entry->sec < segment->t_start)
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continue;
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interpolate.pressure_time += entry->pressure_time;
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if (entry->sec >= segment->t_end)
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break;
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if (i <= cur)
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interpolate.acc_pressure_time += entry->pressure_time;
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}
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return interpolate;
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}
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static void fill_missing_tank_pressures(struct dive *dive, struct plot_info *pi, pr_track_t *track_pr, int cyl)
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{
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int i;
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struct plot_data *entry;
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pr_interpolate_t interpolate = { 0, 0, 0, 0 };
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pr_track_t *last_segment = NULL;
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int cur_pr;
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enum interpolation_strategy strategy;
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/* no segment where this cylinder is used */
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if (!track_pr)
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return;
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if (get_cylinder(dive, cyl)->cylinder_use == OC_GAS)
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strategy = SAC;
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else
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strategy = TIME;
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fill_missing_segment_pressures(track_pr, strategy); // Interpolate the missing tank pressure values ..
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cur_pr = track_pr->start; // in the pr_track_t lists of structures
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// and keep the starting pressure for each cylinder.
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#ifdef DEBUG_PR_TRACK
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dump_pr_track(cyl, track_pr);
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#endif
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/* Transfer interpolated cylinder pressures from pr_track strucktures to plotdata
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* Go down the list of tank pressures in plot_info. Align them with the start &
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* end times of each profile segment represented by a pr_track_t structure. Get
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* the accumulated pressure_depths from the pr_track_t structures and then
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* interpolate the pressure where these do not exist in the plot_info pressure
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* variables. Pressure values are transferred from the pr_track_t structures
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* to the plot_info structure, allowing us to plot the tank pressure.
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*
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* The first two pi structures are "fillers", but in case we don't have a sample
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* at time 0 we need to process the second of them here, therefore i=1 */
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for (i = 1; i < pi->nr; i++) { // For each point on the profile:
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double magic;
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pr_track_t *segment;
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int pressure;
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entry = pi->entry + i;
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pressure = get_plot_pressure(pi, i, cyl);
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if (pressure) { // If there is a valid pressure value,
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last_segment = NULL; // get rid of interpolation data,
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cur_pr = pressure; // set current pressure
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continue; // and skip to next point.
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}
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// If there is NO valid pressure value..
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// Find the pressure segment corresponding to this entry..
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segment = track_pr;
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while (segment && segment->t_end < entry->sec) // Find the track_pr with end time..
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segment = segment->next; // ..that matches the plot_info time (entry->sec)
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// After last segment? All done.
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if (!segment)
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break;
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// Before first segment, or between segments.. Go on, no interpolation.
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if (segment->t_start > entry->sec)
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continue;
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if (!segment->pressure_time) { // Empty segment?
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set_plot_pressure_data(pi, i, SENSOR_PR, cyl, cur_pr);
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// Just use our current pressure
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continue; // and skip to next point.
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}
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// If there is a valid segment but no tank pressure ..
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if (segment == last_segment) {
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interpolate.acc_pressure_time += entry->pressure_time;
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} else {
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// Set up an interpolation structure
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interpolate = get_pr_interpolate_data(segment, pi, i);
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last_segment = segment;
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}
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if(get_cylinder(dive, cyl)->cylinder_use == OC_GAS) {
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/* if this segment has pressure_time, then calculate a new interpolated pressure */
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if (interpolate.pressure_time) {
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/* Overall pressure change over total pressure-time for this segment*/
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magic = (interpolate.end - interpolate.start) / (double)interpolate.pressure_time;
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/* Use that overall pressure change to update the current pressure */
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cur_pr = lrint(interpolate.start + magic * interpolate.acc_pressure_time);
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}
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} else {
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magic = (interpolate.end - interpolate.start) / (segment->t_end - segment->t_start);
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cur_pr = lrint(segment->start + magic * (entry->sec - segment->t_start));
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}
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set_plot_pressure_data(pi, i, INTERPOLATED_PR, cyl, cur_pr); // and store the interpolated data in plot_info
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}
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}
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/*
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* What's the pressure-time between two plot data entries?
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* We're calculating the integral of pressure over time by
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* adding these up.
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*
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* The units won't matter as long as everybody agrees about
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* them, since they'll cancel out - we use this to calculate
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* a constant SAC-rate-equivalent, but we only use it to
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* scale pressures, so it ends up being a unitless scaling
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* factor.
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*/
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static inline int calc_pressure_time(struct dive *dive, struct plot_data *a, struct plot_data *b)
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{
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int time = b->sec - a->sec;
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int depth = (a->depth + b->depth) / 2;
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if (depth <= SURFACE_THRESHOLD)
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return 0;
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return depth_to_mbar(depth, dive) * time;
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}
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#ifdef PRINT_PRESSURES_DEBUG
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// A CCR debugging tool that prints the gas pressures in cylinder 0 and in the diluent cylinder, used in populate_pressure_information():
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static void debug_print_pressures(struct plot_info *pi)
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{
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int i;
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for (i = 0; i < pi->nr; i++)
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printf("%5d |%9d | %9d |\n", i, get_plot_sensor_pressure(pi, i), get_plot_interpolated_pressure(pi, i));
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}
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#endif
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/* This function goes through the list of tank pressures, of structure plot_info for the dive profile where each
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* item in the list corresponds to one point (node) of the profile. It finds values for which there are no tank
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* pressures (pressure==0). For each missing item (node) of tank pressure it creates a pr_track_alloc structure
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* that represents a segment on the dive profile and that contains tank pressures. There is a linked list of
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* pr_track_alloc structures for each cylinder. These pr_track_alloc structures ultimately allow for filling
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* the missing tank pressure values on the dive profile using the depth_pressure of the dive. To do this, it
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* calculates the summed pressure-time value for the duration of the dive and stores these * in the pr_track_alloc
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* structures. This function is called by create_plot_info_new() in profile.c
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*/
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void populate_pressure_information(struct dive *dive, struct divecomputer *dc, struct plot_info *pi, int sensor)
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{
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UNUSED(dc);
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int first, last, cyl;
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cylinder_t *cylinder = get_cylinder(dive, sensor);
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pr_track_t *track = NULL;
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pr_track_t *current = NULL;
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const struct event *ev, *b_ev;
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int missing_pr = 0, dense = 1;
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enum divemode_t dmode = dc->divemode;
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const double gasfactor[5] = {1.0, 0.0, prefs.pscr_ratio/1000.0, 1.0, 1.0 };
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if (sensor < 0 || sensor >= dive->cylinders.nr)
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return;
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/* if we have no pressure data whatsoever, this is pointless, so let's just return */
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if (!cylinder->start.mbar && !cylinder->end.mbar &&
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!cylinder->sample_start.mbar && !cylinder->sample_end.mbar)
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return;
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/* Get a rough range of where we have any pressures at all */
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first = last = -1;
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for (int i = 0; i < pi->nr; i++) {
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int pressure = get_plot_sensor_pressure(pi, i, sensor);
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if (!pressure)
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continue;
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if (first < 0)
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first = i;
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last = i;
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}
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/* No sensor data at all? */
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if (first == last)
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return;
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/*
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* Split the range:
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* - missing pressure data
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* - gas change events to other cylinders
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*
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* Note that we only look at gas switches if this cylinder
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* itself has a gas change event.
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*/
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cyl = sensor;
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ev = NULL;
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if (has_gaschange_event(dive, dc, sensor))
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ev = get_next_event(dc->events, "gaschange");
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b_ev = get_next_event(dc->events, "modechange");
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for (int i = first; i <= last; i++) {
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struct plot_data *entry = pi->entry + i;
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int pressure = get_plot_sensor_pressure(pi, i, sensor);
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int time = entry->sec;
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while (ev && ev->time.seconds <= time) { // Find 1st gaschange event after
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cyl = get_cylinder_index(dive, ev); // the current gas change.
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if (cyl < 0)
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cyl = sensor;
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ev = get_next_event(ev->next, "gaschange");
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}
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while (b_ev && b_ev->time.seconds <= time) { // Keep existing divemode, then
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dmode = b_ev->value; // find 1st divemode change event after the current
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b_ev = get_next_event(b_ev->next, "modechange"); // divemode change.
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}
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if (current) { // calculate pressure-time, taking into account the dive mode for this specific segment.
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entry->pressure_time = (int)(calc_pressure_time(dive, entry - 1, entry) * gasfactor[dmode] + 0.5);
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current->pressure_time += entry->pressure_time;
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current->t_end = entry->sec;
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if (pressure)
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current->end = pressure;
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}
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// We have a final pressure for 'current'
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// If a gas switch has occurred, finish the
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// current pressure track entry and continue
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// until we get back to this cylinder.
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if (cyl != sensor) {
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current = NULL;
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set_plot_pressure_data(pi, i, SENSOR_PR, sensor, 0);
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continue;
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}
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// If we have no pressure information, we will need to
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// continue with or without a tracking entry. Mark any
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// existing tracking entry as non-dense, and remember
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// to fill in interpolated data.
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if (current && !pressure) {
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missing_pr = 1;
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dense = 0;
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continue;
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}
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// If we already have a pressure tracking entry, and
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// it has not had any missing samples, just continue
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// using it - there's nothing to interpolate yet.
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if (current && dense)
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continue;
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// We need to start a new tracking entry, either
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// because the previous was interrupted by a gas
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// switch event, or because the previous one has
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// missing entries that need to be interpolated.
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// Or maybe we didn't have a previous one at all,
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// and this is the first pressure entry.
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current = pr_track_alloc(pressure, entry->sec);
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track = list_add(track, current);
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dense = 1;
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}
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if (missing_pr) {
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fill_missing_tank_pressures(dive, pi, track, sensor);
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}
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#ifdef PRINT_PRESSURES_DEBUG
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debug_print_pressures(pi);
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#endif
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list_free(track);
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}
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