Make gas change events always have a cylinder index

In commit df4e26c8757a ("Start sanitizing gaschange event information")
back about a year and a half ago, I started sanitizing the gas switch
event data, allowing gas switches to be associated with a particular
cylinder index rather than just the gas mix that is switched to.

But that initial step only _allowed_ a gas switch event to be associated
with a particular cylinder, the primary model was still to just specify
the mix.

This finally takes the next step, and *always* associates a gas switch
event with a particular cylinder.  Instead of then looking up the
cylinder by trying to match gas mixes at runtime, subsurface now looks
it up when loading the dive initially as part of the dive fixup code.

The switch event still has an a separate gas mix associated with it, but
this patch also starts preparing for entirely relying on the gas mix in
the cylinder itself, by starting to pass in not just the event but also
the dive pointer to the routines that look up gas mix details.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

1 files changed, 94 insertions, 43 deletions

diff --git a/core/dive.c b/core/dive.c
index 6d4f8603c..915a04fe5 100644
--- a/core/dive.c
+++ b/core/dive.c
@@ -40,28 +40,6 @@ int event_is_gaschange(struct event *ev)
 		ev->type == SAMPLE_EVENT_GASCHANGE2;
 }
 
-/*
- * Does the gas mix data match the legacy
- * libdivecomputer event format? If so,
- * we can skip saving it, in order to maintain
- * the old save formats. We'll re-generate the
- * gas mix when loading.
- */
-int event_gasmix_redundant(struct event *ev)
-{
-	struct gasmix *mix = &ev->gas.mix;
-	int value = ev->value;
-	int o2, he;
-
-	if (value == 21)
-		return gasmix_is_air(mix);
-
-	o2 = (value & 0xffff) * 10;
-	he = (value >> 16) * 10;
-	return	o2 == get_o2(mix) &&
-		he == get_he(mix);
-}
-
 struct event *add_event(struct divecomputer *dc, unsigned int time, int type, int flags, int value, const char *name)
 {
 	int gas_index = -1;
@@ -178,7 +156,7 @@ void add_extra_data(struct divecomputer *dc, const char *key, const char *value)
 }
 
 /* this returns a pointer to static variable - so use it right away after calling */
-struct gasmix *get_gasmix_from_event(struct event *ev)
+struct gasmix *get_gasmix_from_event(struct dive *dive, struct event *ev)
 {
 	static struct gasmix dummy;
 	if (ev && event_is_gaschange(ev))
@@ -849,7 +827,7 @@ int explicit_first_cylinder(struct dive *dive, struct divecomputer *dc)
 /* this gets called when the dive mode has changed (so OC vs. CC)
  * there are two places we might have setpoints... events or in the samples
  */
-void update_setpoint_events(struct divecomputer *dc)
+void update_setpoint_events(struct dive *dive, struct divecomputer *dc)
 {
 	struct event *ev;
 	int new_setpoint = 0;
@@ -867,14 +845,14 @@ void update_setpoint_events(struct divecomputer *dc)
 		// So we make sure, this comes from a Predator or Petrel and we only remove
 		// pO2 values we would have computed anyway.
 		struct event *ev = get_next_event(dc->events, "gaschange");
-		struct gasmix *gasmix = get_gasmix_from_event(ev);
+		struct gasmix *gasmix = get_gasmix_from_event(dive, ev);
 		struct event *next = get_next_event(ev, "gaschange");
 
 		for (int i = 0; i < dc->samples; i++) {
 			struct gas_pressures pressures;
 			if (next && dc->sample[i].time.seconds >= next->time.seconds) {
 				ev = next;
-				gasmix = get_gasmix_from_event(ev);
+				gasmix = get_gasmix_from_event(dive, ev);
 				next = get_next_event(ev, "gaschange");
 			}
 			fill_pressures(&pressures, calculate_depth_to_mbar(dc->sample[i].depth.mm, dc->surface_pressure, 0), gasmix ,0, OC);
@@ -1401,6 +1379,92 @@ static void fixup_dive_pressures(struct dive *dive, struct divecomputer *dc)
 	simplify_dc_pressures(dive, dc);
 }
 
+int find_best_gasmix_match(struct gasmix *mix, cylinder_t array[], unsigned int used)
+{
+	int i;
+	int best = -1, score = INT_MAX;
+
+	for (i = 0; i < MAX_CYLINDERS; i++) {
+		const cylinder_t *match;
+		int distance;
+
+		if (used & (1 << i))
+			continue;
+		match = array + i;
+		if (cylinder_nodata(match))
+			continue;
+		distance = gasmix_distance(mix, &match->gasmix);
+		if (distance >= score)
+			continue;
+		best = i;
+		score = distance;
+	}
+	return best;
+}
+
+/*
+ * Match a gas change event against the cylinders we have
+ */
+static bool validate_gaschange(struct dive *dive, struct divecomputer *dc, struct event *event)
+{
+	int index;
+	int o2, he, value;
+
+	/* We'll get rid of the per-event gasmix, but for now sanitize it */
+	if (gasmix_is_air(&event->gas.mix))
+		event->gas.mix.o2.permille = 0;
+
+	/* Do we already have a cylinder index for this gasmix? */
+	if (event->gas.index >= 0)
+		return true;
+
+	index = find_best_gasmix_match(&event->gas.mix, dive->cylinder, 0);
+	if (index < 0)
+		return false;
+
+	/* Fix up the event to have the right information */
+	event->gas.index = index;
+	event->gas.mix = dive->cylinder[index].gasmix;
+
+	/* Convert to odd libdivecomputer format */
+	o2 = get_o2(&event->gas.mix);
+	he = get_he(&event->gas.mix);
+
+	o2 = (o2 + 5) / 10;
+	he = (he + 5) / 10;
+	value = o2 + (he << 16);
+
+	event->value = value;
+	if (he)
+		event->type = SAMPLE_EVENT_GASCHANGE2;
+
+	return true;
+}
+
+/* Clean up event, return true if event is ok, false if it should be dropped as bogus */
+static bool validate_event(struct dive *dive, struct divecomputer *dc, struct event *event)
+{
+	if (event_is_gaschange(event))
+		return validate_gaschange(dive, dc, event);
+	return true;
+}
+
+static void fixup_dc_gasswitch(struct dive *dive, struct divecomputer *dc)
+{
+	struct event **evp, *event;
+
+	evp = &dc->events;
+	while ((event = *evp) != NULL) {
+		if (validate_event(dive, dc, event)) {
+			evp = &event->next;
+			continue;
+		}
+
+		/* Delete this event and try the next one */
+		*evp = event->next;
+	}
+}
+
 static void fixup_dive_dc(struct dive *dive, struct divecomputer *dc)
 {
 	int i;
@@ -1418,6 +1482,9 @@ static void fixup_dive_dc(struct dive *dive, struct divecomputer *dc)
 	/* Fix up dive temperatures based on dive computer samples */
 	fixup_dc_temp(dive, dc);
 
+	/* Fix up gas switch events */
+	fixup_dc_gasswitch(dive, dc);
+
 	/* Fix up cylinder sensor data */
 	fixup_dc_cylinder_index(dive, dc);
 
@@ -1804,25 +1871,9 @@ extern void fill_pressures(struct gas_pressures *pressures, const double amb_pre
 
 static int find_cylinder_match(cylinder_t *cyl, cylinder_t array[], unsigned int used)
 {
-	int i;
-	int best = -1, score = INT_MAX;
-
 	if (cylinder_nodata(cyl))
 		return -1;
-	for (i = 0; i < MAX_CYLINDERS; i++) {
-		const cylinder_t *match;
-		int distance;
-
-		if (used & (1 << i))
-			continue;
-		match = array + i;
-		distance = gasmix_distance(&cyl->gasmix, &match->gasmix);
-		if (distance >= score)
-			continue;
-		best = i;
-		score = distance;
-	}
-	return best;
+	return find_best_gasmix_match(&cyl->gasmix, array, used);
 }
 
 /* Force an initial gaschange event to the (old) gas #0 */