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garmin: report per-tank gas-consumption usage via DC_FIELD_TANK #145

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Merged
mikeller merged 2 commits into from
Oct 15, 2026
Merged

garmin: report per-tank gas-consumption usage via DC_FIELD_TANK #145

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1991fc8
garmin: report per-tank gas-consumption usage via DC_FIELD_TANK
mikeller Oct 13, 2026
590d585
examples: fix tank usage XML labels to match dc_tank_usage_t
mikeller Oct 13, 2026
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2 changes: 1 addition & 1 deletion examples/output_xml.c
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Original file line number Diff line number Diff line change
Expand Up @@ -414,7 +414,7 @@ dctool_xml_output_write (dctool_output_t *abstract, dc_parser_t *parser, const u
tank.gasmix);
}
if (tank.usage) {
const char *usage[] = {"none", "oxygen", "diluent", "sidemount"};
const char *usage[] = {"none", "sidemount", "included", "excluded"};
fprintf (output->ostream,
" <usage>%s</usage>\n",
usage[tank.usage]);
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8 changes: 7 additions & 1 deletion include/libdivecomputer/parser.h
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Expand Up @@ -230,8 +230,14 @@ typedef unsigned int dc_tankinfo_t;
*/

typedef enum dc_tank_usage_t {
DC_TANK_USAGE_NONE,
DC_TANK_USAGE_NONE, /* Not specified, or unknown. */
DC_TANK_USAGE_SIDEMOUNT,
DC_TANK_USAGE_INCLUDED, /* The dive computer counts this tank towards
the diver's own gas consumption. */
DC_TANK_USAGE_EXCLUDED, /* The dive computer does not count this tank
towards the diver's own gas consumption
(for example a buddy's or a stage/deco
Comment on lines +235 to +239

@mikeller mikeller Oct 13, 2026

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Good catch, thank you. examples/output_xml.c's tank-reporting block prints tank.usage (a dc_tank_usage_t) through the array built for the unrelated dc_usage_t gas-mix mapping, {"none", "oxygen", "diluent", "sidemount"}, so DC_TANK_USAGE_INCLUDED would print as "diluent" and DC_TANK_USAGE_EXCLUDED as "sidemount".

This will be fixed by giving the tank-reporting block its own mapping, {"none", "sidemount", "included", "excluded"}, matching dc_tank_usage_t's actual enumerator order, without touching the separate gas-mix block.

@mikeller mikeller Oct 14, 2026

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This has been fixed in commit 590d585 ("examples: fix tank usage XML labels to match dc_tank_usage_t"), which is already part of this PR. The tank-reporting block now has its own usage[] array, {"none", "sidemount", "included", "excluded"}, matching dc_tank_usage_t's actual enumerator order, and no longer reuses the unrelated gas-mix dc_usage_t mapping.

bottle that is tracked but not included). */
} dc_tank_usage_t;

typedef struct dc_tank_t {
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3 changes: 3 additions & 0 deletions src/field-cache.c
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Expand Up @@ -124,6 +124,9 @@ dc_field_get(dc_field_cache_t *cache, dc_field_type_t type, unsigned int flags,
tank->gasmix = flags;
tank->workpressure = cache->tankworkingpressure[flags];
tank->type = cache->tankinfo[flags];
tank->usage = cache->tankusage[flags];
tank->beginpressure = 0;
tank->endpressure = 0;

return DC_STATUS_SUCCESS;
case DC_FIELD_STRING:
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35 changes: 30 additions & 5 deletions src/garmin_parser.c
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Expand Up @@ -54,6 +54,13 @@ struct garmin_sensor {
unsigned int sensor_id;
const char *sensor_name;
unsigned char sensor_enabled, sensor_units, sensor_used_for_gas_rate;
// SENSOR_PROFILE field 78 (used_for_gas_rate) is only decoded when
// the log actually contains it: the field-decoding machinery drops
// absent/invalid (0xff) values before the handler runs, and this
// whole struct is memset to zero otherwise. So a raw 0 is ambiguous
// between "device said not counted" and "device said nothing", and
// we need this separate flag to tell the two apart.
unsigned char sensor_used_for_gas_rate_valid;
unsigned int sensor_rated_pressure, sensor_reserve_pressure, sensor_volume;
};

Expand Down Expand Up @@ -855,7 +862,9 @@ DECLARE_FIELD(SENSOR_PROFILE, volume, UINT16)
}
DECLARE_FIELD(SENSOR_PROFILE, used_for_gas_rate, ENUM)
{
current_sensor(garmin)->sensor_used_for_gas_rate = data;
struct garmin_sensor *sensor = current_sensor(garmin);
sensor->sensor_used_for_gas_rate = data;
sensor->sensor_used_for_gas_rate_valid = 1;
}

DECLARE_FIELD(TANK_UPDATE, sensor, UINT32Z)
Expand Down Expand Up @@ -1725,12 +1734,28 @@ garmin_parser_set_data (garmin_parser_t *garmin, const unsigned char *data, unsi

add_gps_string(garmin, "Record GPS", &garmin->gps.RECORD);

// We have no idea about gas mixes vs tanks
// We have no idea about gas mixes vs tanks, so for now the only
// DC_FIELD_TANK member we report is "usage": whether the dive
// computer counted this tank pod's gas towards the diver's own
// consumption (SENSOR_PROFILE field 78, "used for SAC calculations").
// Volume/type/workpressure are left at their field-cache defaults.
//
// The index here matches the one used for DC_SAMPLE_PRESSURE
// (see find_tank_index()): both walk garmin->dive.sensor[].
for (int i = 0; i < garmin->dive.nr_sensor; i++) {
// DC_ASSIGN_IDX(garmin->cache, tankinfo, i, ..);
// DC_ASSIGN_IDX(garmin->cache, tanksize, i, ..);
// DC_ASSIGN_IDX(garmin->cache, tankworkingpressure, i, ..);
const struct garmin_sensor *sensor = garmin->dive.sensor + i;
dc_tank_usage_t usage = DC_TANK_USAGE_NONE;

// Field 78 is only decoded when it is actually present in the
// log; a sensor that never saw it must stay NONE here, never
// EXCLUDED.
if (sensor->sensor_used_for_gas_rate_valid)
usage = sensor->sensor_used_for_gas_rate ? DC_TANK_USAGE_INCLUDED : DC_TANK_USAGE_EXCLUDED;

garmin->cache.tankusage[i] = usage;
}
if (garmin->dive.nr_sensor)
garmin->cache.initialized |= 1u << DC_FIELD_TANK;

// Hate hate hate gasmix vs tank counts.
//
Expand Down
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