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220 lines
6 KiB
C
220 lines
6 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <string.h>
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#include "dive.h"
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#include "subsurface-string.h"
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#include "device.h"
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/*
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* Good fake dive profiles are hard.
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*
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* "depthtime" is the integral of the dive depth over
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* time ("area" of the dive profile). We want that
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* area to match the average depth (avg_d*max_t).
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*
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* To do that, we generate a 6-point profile:
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*
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* (0, 0)
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* (t1, max_d)
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* (t2, max_d)
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* (t3, d)
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* (t4, d)
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* (max_t, 0)
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*
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* with the same ascent/descent rates between the
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* different depths.
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*
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* NOTE: avg_d, max_d and max_t are given constants.
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* The rest we can/should play around with to get a
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* good-looking profile.
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*
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* That six-point profile gives a total area of:
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*
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* (max_d*max_t) - (max_d*t1) - (max_d-d)*(t4-t3)
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*
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* And the "same ascent/descent rates" requirement
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* gives us (time per depth must be same):
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*
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* t1 / max_d = (t3-t2) / (max_d-d)
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* t1 / max_d = (max_t-t4) / d
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*
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* We also obviously require:
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*
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* 0 <= t1 <= t2 <= t3 <= t4 <= max_t
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*
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* Let us call 'd_frac = d / max_d', and we get:
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*
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* Total area must match average depth-time:
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*
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* (max_d*max_t) - (max_d*t1) - (max_d-d)*(t4-t3) = avg_d*max_t
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* max_d*(max_t-t1-(1-d_frac)*(t4-t3)) = avg_d*max_t
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* max_t-t1-(1-d_frac)*(t4-t3) = avg_d*max_t/max_d
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* t1+(1-d_frac)*(t4-t3) = max_t*(1-avg_d/max_d)
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*
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* and descent slope must match ascent slopes:
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*
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* t1 / max_d = (t3-t2) / (max_d*(1-d_frac))
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* t1 = (t3-t2)/(1-d_frac)
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*
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* and
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*
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* t1 / max_d = (max_t-t4) / (max_d*d_frac)
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* t1 = (max_t-t4)/d_frac
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*
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* In general, we have more free variables than we have constraints,
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* but we can aim for certain basics, like a good ascent slope.
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*/
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static int fill_samples(struct sample *s, int max_d, int avg_d, int max_t, double slope, double d_frac)
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{
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double t_frac = max_t * (1 - avg_d / (double)max_d);
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int t1 = lrint(max_d / slope);
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int t4 = lrint(max_t - t1 * d_frac);
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int t3 = lrint(t4 - (t_frac - t1) / (1 - d_frac));
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int t2 = lrint(t3 - t1 * (1 - d_frac));
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if (t1 < 0 || t1 > t2 || t2 > t3 || t3 > t4 || t4 > max_t)
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return 0;
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s[1].time.seconds = t1;
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s[1].depth.mm = max_d;
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s[2].time.seconds = t2;
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s[2].depth.mm = max_d;
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s[3].time.seconds = t3;
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s[3].depth.mm = lrint(max_d * d_frac);
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s[4].time.seconds = t4;
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s[4].depth.mm = lrint(max_d * d_frac);
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return 1;
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}
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/* we have no average depth; instead of making up a random average depth
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* we should assume either a PADI rectangular profile (for short and/or
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* shallow dives) or more reasonably a six point profile with a 3 minute
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* safety stop at 5m */
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static void fill_samples_no_avg(struct sample *s, int max_d, int max_t, double slope)
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{
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// shallow or short dives are just trapecoids based on the given slope
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if (max_d < 10000 || max_t < 600) {
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s[1].time.seconds = lrint(max_d / slope);
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s[1].depth.mm = max_d;
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s[2].time.seconds = max_t - lrint(max_d / slope);
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s[2].depth.mm = max_d;
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} else {
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s[1].time.seconds = lrint(max_d / slope);
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s[1].depth.mm = max_d;
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s[2].time.seconds = max_t - lrint(max_d / slope) - 180;
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s[2].depth.mm = max_d;
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s[3].time.seconds = max_t - lrint(5000 / slope) - 180;
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s[3].depth.mm = 5000;
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s[4].time.seconds = max_t - lrint(5000 / slope);
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s[4].depth.mm = 5000;
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}
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}
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void fake_dc(struct divecomputer *dc)
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{
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alloc_samples(dc, 6);
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struct sample *fake = dc->sample;
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int i;
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dc->samples = 6;
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/* The dive has no samples, so create a few fake ones */
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int max_t = dc->duration.seconds;
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int max_d = dc->maxdepth.mm;
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int avg_d = dc->meandepth.mm;
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memset(fake, 0, 6 * sizeof(struct sample));
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fake[5].time.seconds = max_t;
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for (i = 0; i < 6; i++) {
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fake[i].bearing.degrees = -1;
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fake[i].ndl.seconds = -1;
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}
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if (!max_t || !max_d) {
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dc->samples = 0;
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return;
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}
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/* Set last manually entered time to the total dive length */
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dc->last_manual_time = dc->duration;
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/*
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* We want to fake the profile so that the average
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* depth ends up correct. However, in the absence of
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* a reasonable average, let's just make something
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* up. Note that 'avg_d == max_d' is _not_ a reasonable
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* average.
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* We explicitly treat avg_d == 0 differently */
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if (avg_d == 0) {
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/* we try for a sane slope, but bow to the insanity of
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* the user supplied data */
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fill_samples_no_avg(fake, max_d, max_t, MAX(2.0 * max_d / max_t, (double)prefs.ascratelast6m));
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if (fake[3].time.seconds == 0) { // just a 4 point profile
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dc->samples = 4;
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fake[3].time.seconds = max_t;
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}
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return;
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}
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if (avg_d < max_d / 10 || avg_d >= max_d) {
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avg_d = (max_d + 10000) / 3;
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if (avg_d > max_d)
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avg_d = max_d * 2 / 3;
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}
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if (!avg_d)
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avg_d = 1;
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/*
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* Ok, first we try a basic profile with a specific ascent
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* rate (5 meters per minute) and d_frac (1/3).
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*/
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if (fill_samples(fake, max_d, avg_d, max_t, (double)prefs.ascratelast6m, 0.33))
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return;
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/*
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* Ok, assume that didn't work because we cannot make the
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* average come out right because it was a quick deep dive
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* followed by a much shallower region
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*/
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if (fill_samples(fake, max_d, avg_d, max_t, 10000.0 / 60, 0.10))
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return;
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/*
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* Uhhuh. That didn't work. We'd need to find a good combination that
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* satisfies our constraints. Currently, we don't, we just give insane
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* slopes.
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*/
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if (fill_samples(fake, max_d, avg_d, max_t, 10000.0, 0.01))
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return;
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/* Even that didn't work? Give up, there's something wrong */
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}
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static void match_id(void *_dc, const char *model, uint32_t deviceid,
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const char *nickname, const char *serial, const char *firmware)
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{
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// here nickname is unused
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(void)nickname;
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struct divecomputer *dc = _dc;
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if (dc->deviceid != deviceid)
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return;
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if (!model || !dc->model || strcmp(dc->model, model))
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return;
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if (serial && !dc->serial)
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dc->serial = strdup(serial);
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if (firmware && !dc->fw_version)
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dc->fw_version = strdup(firmware);
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}
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/*
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* When setting the device ID, we also fill in the
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* serial number and firmware version data
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*/
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void set_dc_deviceid(struct divecomputer *dc, unsigned int deviceid)
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{
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if (deviceid) {
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dc->deviceid = deviceid;
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call_for_each_dc(dc, match_id, false);
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}
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}
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