diff options
| -rw-r--r-- | divelist.c | 72 |
1 files changed, 71 insertions, 1 deletions
diff --git a/divelist.c b/divelist.c index 61b9116b2..13ed5113f 100644 --- a/divelist.c +++ b/divelist.c @@ -273,7 +273,7 @@ static int active_o2(struct dive *dive, struct divecomputer *dc, duration_t time return o2permille; } -/* calculate OTU for a dive - this only takes the first diveomputer into account */ +/* calculate OTU for a dive - this only takes the first divecomputer into account */ static int calculate_otu(struct dive *dive) { int i; @@ -297,6 +297,74 @@ static int calculate_otu(struct dive *dive) } return otu + 0.5; } +/* calculate CNS for a dive - this only takes the first divecomputer into account */ +int const cns_table[][3] = { +/* po2, Maximum Single Exposure, Maximum 24 hour Exposure */ + {1600, 45 * 60, 150 * 60}, + {1500, 120 * 60, 180 * 60}, + {1400, 150 * 60, 180 * 60}, + {1300, 180 * 60, 210 * 60}, + {1200, 210 * 60, 240 * 60}, + {1100, 240 * 60, 270 * 60}, + {1000, 300 * 60, 300 * 60}, + { 900, 360 * 60, 360 * 60}, + { 800, 450 * 60, 450 * 60}, + { 700, 570 * 60, 570 * 60}, + { 600, 720 * 60, 720 * 60} +}; + +/* this only gets called if dive->maxcns == 0 which means we know that + * none of the divecomputers has tracked any CNS for us + * so we calculated it "by hand" */ +static int calculate_cns(struct dive *dive) +{ + int i, j, divenr; + double cns = 0.0; + struct divecomputer *dc = &dive->dc; + struct dive *prev_dive; + timestamp_t endtime; + + /* shortcut */ + if (dive->cns) + return dive->cns; + /* + * Do we start with a cns loading from a privious dive? + * Check if we did a dive 12 hours prior, and what cns we had from that. + * Then apply ha 90min halftime to see whats left. + */ + divenr = get_divenr(dive); + if (divenr) { + prev_dive = get_dive(divenr -1 ); + endtime = prev_dive->when + prev_dive->duration.seconds; + if (prev_dive && dive->when < (endtime + 3600 * 12)) { + cns = calculate_cns(prev_dive); + cns = cns * 1/pow(2, (dive->when - endtime) / (90.0 * 60.0)); + } + } + /* Caclulate the cns for each sample in this dive and sum them */ + for (i = 1; i < dc->samples; i++) { + int t; + int po2; + struct sample *sample = dc->sample + i; + struct sample *psample = sample - 1; + t = sample->time.seconds - psample->time.seconds; + if (sample->po2) { + po2 = sample->po2; + } else { + int o2 = active_o2(dive, dc, sample->time); + po2 = o2 / 1000.0 * depth_to_mbar(sample->depth.mm, dive); + } + /* Find what table-row we should calculate % for */ + for (j = 1; j < sizeof(cns_table)/(sizeof(int) * 3); j++) + if (po2 > cns_table[j][0]) + break; + j--; + cns += ((double)t)/((double)cns_table[j][1]) * 100; + } + /* save calculated cns in dive struct */ + dive->cns = cns; + return dive->cns; +} /* * Return air usage (in liters). */ @@ -456,6 +524,8 @@ void update_cylinder_related_info(struct dive *dive) if (dive != NULL) { dive->sac = calculate_sac(dive); dive->otu = calculate_otu(dive); + if (dive->maxcns == 0) + dive->maxcns = calculate_cns(dive); } } |