Move subsurface-core to core and qt-mobile to mobile-widgets

Having subsurface-core as a directory name really messes with
autocomplete and is obviously redundant. Simmilarly, qt-mobile caused an
autocomplete conflict and also was inconsistent with the desktop-widget
name for the directory containing the "other" UI.

And while cleaning up the resulting change in the path name for include
files, I decided to clean up those even more to make them consistent
overall.

This could have been handled in more commits, but since this requires a
make clean before the build, it seemed more sensible to do it all in one.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

1 files changed, 3561 insertions, 0 deletions

diff --git a/core/dive.c b/core/dive.c
new file mode 100644
index 000000000..ce730da28
--- /dev/null
+++ b/core/dive.c
@@ -0,0 +1,3561 @@
+/* dive.c */
+/* maintains the internal dive list structure */
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <limits.h>
+#include "gettext.h"
+#include "dive.h"
+#include "libdivecomputer.h"
+#include "device.h"
+#include "divelist.h"
+#include "qthelperfromc.h"
+
+/* one could argue about the best place to have this variable -
+ * it's used in the UI, but it seems to make the most sense to have it
+ * here */
+struct dive displayed_dive;
+struct dive_site displayed_dive_site;
+
+struct tag_entry *g_tag_list = NULL;
+
+static const char *default_tags[] = {
+	QT_TRANSLATE_NOOP("gettextFromC", "boat"), QT_TRANSLATE_NOOP("gettextFromC", "shore"), QT_TRANSLATE_NOOP("gettextFromC", "drift"),
+	QT_TRANSLATE_NOOP("gettextFromC", "deep"), QT_TRANSLATE_NOOP("gettextFromC", "cavern"), QT_TRANSLATE_NOOP("gettextFromC", "ice"),
+	QT_TRANSLATE_NOOP("gettextFromC", "wreck"), QT_TRANSLATE_NOOP("gettextFromC", "cave"), QT_TRANSLATE_NOOP("gettextFromC", "altitude"),
+	QT_TRANSLATE_NOOP("gettextFromC", "pool"), QT_TRANSLATE_NOOP("gettextFromC", "lake"), QT_TRANSLATE_NOOP("gettextFromC", "river"),
+	QT_TRANSLATE_NOOP("gettextFromC", "night"), QT_TRANSLATE_NOOP("gettextFromC", "fresh"), QT_TRANSLATE_NOOP("gettextFromC", "student"),
+	QT_TRANSLATE_NOOP("gettextFromC", "instructor"), QT_TRANSLATE_NOOP("gettextFromC", "photo"), QT_TRANSLATE_NOOP("gettextFromC", "video"),
+	QT_TRANSLATE_NOOP("gettextFromC", "deco")
+};
+
+const char *cylinderuse_text[] = {
+	QT_TRANSLATE_NOOP("gettextFromC", "OC-gas"), QT_TRANSLATE_NOOP("gettextFromC", "diluent"), QT_TRANSLATE_NOOP("gettextFromC", "oxygen")
+};
+const char *divemode_text[] = { "OC", "CCR", "PSCR", "Freedive" };
+
+int event_is_gaschange(struct event *ev)
+{
+	return ev->type == SAMPLE_EVENT_GASCHANGE ||
+		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)
+{
+	int value = ev->value;
+	int o2, he;
+
+	o2 = (value & 0xffff) * 10;
+	he = (value >> 16) * 10;
+	return	o2 == ev->gas.mix.o2.permille &&
+		he == ev->gas.mix.he.permille;
+}
+
+struct event *add_event(struct divecomputer *dc, unsigned int time, int type, int flags, int value, const char *name)
+{
+	int gas_index = -1;
+	struct event *ev, **p;
+	unsigned int size, len = strlen(name);
+
+	size = sizeof(*ev) + len + 1;
+	ev = malloc(size);
+	if (!ev)
+		return NULL;
+	memset(ev, 0, size);
+	memcpy(ev->name, name, len);
+	ev->time.seconds = time;
+	ev->type = type;
+	ev->flags = flags;
+	ev->value = value;
+
+	/*
+	 * Expand the events into a sane format. Currently
+	 * just gas switches
+	 */
+	switch (type) {
+	case SAMPLE_EVENT_GASCHANGE2:
+		/* High 16 bits are He percentage */
+		ev->gas.mix.he.permille = (value >> 16) * 10;
+
+		/* Extension to the GASCHANGE2 format: cylinder index in 'flags' */
+		if (flags > 0 && flags <= MAX_CYLINDERS)
+			gas_index = flags-1;
+	/* Fallthrough */
+	case SAMPLE_EVENT_GASCHANGE:
+		/* Low 16 bits are O2 percentage */
+		ev->gas.mix.o2.permille = (value & 0xffff) * 10;
+		ev->gas.index = gas_index;
+		break;
+	}
+
+	p = &dc->events;
+
+	/* insert in the sorted list of events */
+	while (*p && (*p)->time.seconds <= time)
+		p = &(*p)->next;
+	ev->next = *p;
+	*p = ev;
+	remember_event(name);
+	return ev;
+}
+
+static int same_event(struct event *a, struct event *b)
+{
+	if (a->time.seconds != b->time.seconds)
+		return 0;
+	if (a->type != b->type)
+		return 0;
+	if (a->flags != b->flags)
+		return 0;
+	if (a->value != b->value)
+		return 0;
+	return !strcmp(a->name, b->name);
+}
+
+void remove_event(struct event *event)
+{
+	struct event **ep = &current_dc->events;
+	while (ep && !same_event(*ep, event))
+		ep = &(*ep)->next;
+	if (ep) {
+		/* we can't link directly with event->next
+		 * because 'event' can be a copy from another
+		 * dive (for instance the displayed_dive
+		 * that we use on the interface to show things). */
+		struct event *temp = (*ep)->next;
+		free(*ep);
+		*ep = temp;
+	}
+}
+
+/* since the name is an array as part of the structure (how silly is that?) we
+ * have to actually remove the existing event and replace it with a new one.
+ * WARNING, WARNING... this may end up freeing event in case that event is indeed
+ * WARNING, WARNING... part of this divecomputer on this dive! */
+void update_event_name(struct dive *d, struct event *event, char *name)
+{
+	if (!d || !event)
+		return;
+	struct divecomputer *dc = get_dive_dc(d, dc_number);
+	if (!dc)
+		return;
+	struct event **removep = &dc->events;
+	struct event *remove;
+	while ((*removep)->next && !same_event(*removep, event))
+		removep = &(*removep)->next;
+	if (!same_event(*removep, event))
+		return;
+	remove = *removep;
+	*removep = (*removep)->next;
+	add_event(dc, event->time.seconds, event->type, event->flags, event->value, name);
+	free(remove);
+	invalidate_dive_cache(d);
+}
+
+void add_extra_data(struct divecomputer *dc, const char *key, const char *value)
+{
+	struct extra_data **ed = &dc->extra_data;
+
+	while (*ed)
+		ed = &(*ed)->next;
+	*ed = malloc(sizeof(struct extra_data));
+	if (*ed) {
+		(*ed)->key = strdup(key);
+		(*ed)->value = strdup(value);
+		(*ed)->next = NULL;
+	}
+}
+
+/* this returns a pointer to static variable - so use it right away after calling */
+struct gasmix *get_gasmix_from_event(struct event *ev)
+{
+	static struct gasmix dummy;
+	if (ev && event_is_gaschange(ev))
+		return &ev->gas.mix;
+
+	return &dummy;
+}
+
+int get_pressure_units(int mb, const char **units)
+{
+	int pressure;
+	const char *unit;
+	struct units *units_p = get_units();
+
+	switch (units_p->pressure) {
+	case PASCAL:
+		pressure = mb * 100;
+		unit = translate("gettextFromC", "pascal");
+		break;
+	case BAR:
+	default:
+		pressure = (mb + 500) / 1000;
+		unit = translate("gettextFromC", "bar");
+		break;
+	case PSI:
+		pressure = mbar_to_PSI(mb);
+		unit = translate("gettextFromC", "psi");
+		break;
+	}
+	if (units)
+		*units = unit;
+	return pressure;
+}
+
+double get_temp_units(unsigned int mk, const char **units)
+{
+	double deg;
+	const char *unit;
+	struct units *units_p = get_units();
+
+	if (units_p->temperature == FAHRENHEIT) {
+		deg = mkelvin_to_F(mk);
+		unit = UTF8_DEGREE "F";
+	} else {
+		deg = mkelvin_to_C(mk);
+		unit = UTF8_DEGREE "C";
+	}
+	if (units)
+		*units = unit;
+	return deg;
+}
+
+double get_volume_units(unsigned int ml, int *frac, const char **units)
+{
+	int decimals;
+	double vol;
+	const char *unit;
+	struct units *units_p = get_units();
+
+	switch (units_p->volume) {
+	case LITER:
+	default:
+		vol = ml / 1000.0;
+		unit = translate("gettextFromC", "ℓ");
+		decimals = 1;
+		break;
+	case CUFT:
+		vol = ml_to_cuft(ml);
+		unit = translate("gettextFromC", "cuft");
+		decimals = 2;
+		break;
+	}
+	if (frac)
+		*frac = decimals;
+	if (units)
+		*units = unit;
+	return vol;
+}
+
+int units_to_sac(double volume)
+{
+	if (get_units()->volume == CUFT)
+		return rint(cuft_to_l(volume) * 1000.0);
+	else
+		return rint(volume * 1000);
+}
+
+unsigned int units_to_depth(double depth)
+{
+	if (get_units()->length == METERS)
+		return rint(depth * 1000);
+	return feet_to_mm(depth);
+}
+
+double get_depth_units(int mm, int *frac, const char **units)
+{
+	int decimals;
+	double d;
+	const char *unit;
+	struct units *units_p = get_units();
+
+	switch (units_p->length) {
+	case METERS:
+	default:
+		d = mm / 1000.0;
+		unit = translate("gettextFromC", "m");
+		decimals = d < 20;
+		break;
+	case FEET:
+		d = mm_to_feet(mm);
+		unit = translate("gettextFromC", "ft");
+		decimals = 0;
+		break;
+	}
+	if (frac)
+		*frac = decimals;
+	if (units)
+		*units = unit;
+	return d;
+}
+
+double get_vertical_speed_units(unsigned int mms, int *frac, const char **units)
+{
+	double d;
+	const char *unit;
+	const struct units *units_p = get_units();
+	const double time_factor = units_p->vertical_speed_time == MINUTES ? 60.0 : 1.0;
+
+	switch (units_p->length) {
+	case METERS:
+	default:
+		d = mms / 1000.0 * time_factor;
+		if (units_p->vertical_speed_time == MINUTES)
+			unit = translate("gettextFromC", "m/min");
+		else
+			unit = translate("gettextFromC", "m/s");
+		break;
+	case FEET:
+		d = mm_to_feet(mms) * time_factor;
+		if (units_p->vertical_speed_time == MINUTES)
+			unit = translate("gettextFromC", "ft/min");
+		else
+			unit = translate("gettextFromC", "ft/s");
+		break;
+	}
+	if (frac)
+		*frac = d < 10;
+	if (units)
+		*units = unit;
+	return d;
+}
+
+double get_weight_units(unsigned int grams, int *frac, const char **units)
+{
+	int decimals;
+	double value;
+	const char *unit;
+	struct units *units_p = get_units();
+
+	if (units_p->weight == LBS) {
+		value = grams_to_lbs(grams);
+		unit = translate("gettextFromC", "lbs");
+		decimals = 0;
+	} else {
+		value = grams / 1000.0;
+		unit = translate("gettextFromC", "kg");
+		decimals = 1;
+	}
+	if (frac)
+		*frac = decimals;
+	if (units)
+		*units = unit;
+	return value;
+}
+
+bool has_hr_data(struct divecomputer *dc)
+{
+	int i;
+	struct sample *sample;
+
+	if (!dc)
+		return false;
+
+	sample = dc->sample;
+	for (i = 0; i < dc->samples; i++)
+		if (sample[i].heartbeat)
+			return true;
+	return false;
+}
+
+struct dive *alloc_dive(void)
+{
+	struct dive *dive;
+
+	dive = malloc(sizeof(*dive));
+	if (!dive)
+		exit(1);
+	memset(dive, 0, sizeof(*dive));
+	dive->id = dive_getUniqID(dive);
+	return dive;
+}
+
+static void free_dc(struct divecomputer *dc);
+static void free_pic(struct picture *picture);
+
+/* this is very different from the copy_divecomputer later in this file;
+ * this function actually makes full copies of the content */
+static void copy_dc(struct divecomputer *sdc, struct divecomputer *ddc)
+{
+	*ddc = *sdc;
+	ddc->model = copy_string(sdc->model);
+	copy_samples(sdc, ddc);
+	copy_events(sdc, ddc);
+}
+
+/* copy an element in a list of pictures */
+static void copy_pl(struct picture *sp, struct picture *dp)
+{
+	*dp = *sp;
+	dp->filename = copy_string(sp->filename);
+	dp->hash = copy_string(sp->hash);
+}
+
+/* copy an element in a list of tags */
+static void copy_tl(struct tag_entry *st, struct tag_entry *dt)
+{
+	dt->tag = malloc(sizeof(struct divetag));
+	dt->tag->name = copy_string(st->tag->name);
+	dt->tag->source = copy_string(st->tag->source);
+}
+
+/* Clear everything but the first element;
+ * this works for taglist, picturelist, even dive computers */
+#define STRUCTURED_LIST_FREE(_type, _start, _free) \
+	{                                          \
+		_type *_ptr = _start;              \
+		while (_ptr) {                     \
+			_type *_next = _ptr->next; \
+			_free(_ptr);               \
+			_ptr = _next;              \
+		}                                  \
+	}
+
+#define STRUCTURED_LIST_COPY(_type, _first, _dest, _cpy) \
+	{                                                \
+		_type *_sptr = _first;                   \
+		_type **_dptr = &_dest;                  \
+		while (_sptr) {                          \
+			*_dptr = malloc(sizeof(_type));  \
+			_cpy(_sptr, *_dptr);             \
+			_sptr = _sptr->next;             \
+			_dptr = &(*_dptr)->next;         \
+		}                                        \
+		*_dptr = 0;                              \
+	}
+
+/* copy_dive makes duplicates of many components of a dive;
+ * in order not to leak memory, we need to free those .
+ * copy_dive doesn't play with the divetrip and forward/backward pointers
+ * so we can ignore those */
+void clear_dive(struct dive *d)
+{
+	if (!d)
+		return;
+	/* free the strings */
+	free(d->buddy);
+	free(d->divemaster);
+	free(d->notes);
+	free(d->suit);
+	/* free tags, additional dive computers, and pictures */
+	taglist_free(d->tag_list);
+	STRUCTURED_LIST_FREE(struct divecomputer, d->dc.next, free_dc);
+	STRUCTURED_LIST_FREE(struct picture, d->picture_list, free_pic);
+	for (int i = 0; i < MAX_CYLINDERS; i++)
+		free((void *)d->cylinder[i].type.description);
+	for (int i = 0; i < MAX_WEIGHTSYSTEMS; i++)
+		free((void *)d->weightsystem[i].description);
+	memset(d, 0, sizeof(struct dive));
+}
+
+/* make a true copy that is independent of the source dive;
+ * all data structures are duplicated, so the copy can be modified without
+ * any impact on the source */
+void copy_dive(struct dive *s, struct dive *d)
+{
+	clear_dive(d);
+	/* simply copy things over, but then make actual copies of the
+	 * relevant components that are referenced through pointers,
+	 * so all the strings and the structured lists */
+	*d = *s;
+	invalidate_dive_cache(d);
+	d->buddy = copy_string(s->buddy);
+	d->divemaster = copy_string(s->divemaster);
+	d->notes = copy_string(s->notes);
+	d->suit = copy_string(s->suit);
+	for (int i = 0; i < MAX_CYLINDERS; i++)
+		d->cylinder[i].type.description = copy_string(s->cylinder[i].type.description);
+	for (int i = 0; i < MAX_WEIGHTSYSTEMS; i++)
+		d->weightsystem[i].description = copy_string(s->weightsystem[i].description);
+	STRUCTURED_LIST_COPY(struct picture, s->picture_list, d->picture_list, copy_pl);
+	STRUCTURED_LIST_COPY(struct tag_entry, s->tag_list, d->tag_list, copy_tl);
+
+	// Copy the first dc explicitly, then the list of subsequent dc's
+	copy_dc(&s->dc, &d->dc);
+	STRUCTURED_LIST_COPY(struct divecomputer, s->dc.next, d->dc.next, copy_dc);
+}
+
+/* make a clone of the source dive and clean out the source dive;
+ * this is specifically so we can create a dive in the displayed_dive and then
+ * add it to the divelist.
+ * Note the difference to copy_dive() / clean_dive() */
+struct dive *clone_dive(struct dive *s)
+{
+	struct dive *dive = alloc_dive();
+	*dive = *s;			   // so all the pointers in dive point to the things s pointed to
+	memset(s, 0, sizeof(struct dive)); // and now the pointers in s are gone
+	return dive;
+}
+
+#define CONDITIONAL_COPY_STRING(_component) \
+	if (what._component)                \
+		d->_component = copy_string(s->_component)
+
+// copy elements, depending on bits in what that are set
+void selective_copy_dive(struct dive *s, struct dive *d, struct dive_components what, bool clear)
+{
+	if (clear)
+		clear_dive(d);
+	CONDITIONAL_COPY_STRING(notes);
+	CONDITIONAL_COPY_STRING(divemaster);
+	CONDITIONAL_COPY_STRING(buddy);
+	CONDITIONAL_COPY_STRING(suit);
+	if (what.rating)
+		d->rating = s->rating;
+	if (what.visibility)
+		d->visibility = s->visibility;
+	if (what.divesite)
+		d->dive_site_uuid = s->dive_site_uuid;
+	if (what.tags)
+		STRUCTURED_LIST_COPY(struct tag_entry, s->tag_list, d->tag_list, copy_tl);
+	if (what.cylinders)
+		copy_cylinders(s, d, false);
+	if (what.weights)
+		for (int i = 0; i < MAX_WEIGHTSYSTEMS; i++) {
+			free((void *)d->weightsystem[i].description);
+			d->weightsystem[i] = s->weightsystem[i];
+			d->weightsystem[i].description = copy_string(s->weightsystem[i].description);
+		}
+}
+#undef CONDITIONAL_COPY_STRING
+
+struct event *clone_event(const struct event *src_ev)
+{
+	struct event *ev;
+	if (!src_ev)
+		return NULL;
+
+	size_t size = sizeof(*src_ev) + strlen(src_ev->name) + 1;
+	ev = (struct event*) malloc(size);
+	if (!ev)
+		exit(1);
+	memcpy(ev, src_ev, size);
+	ev->next = NULL;
+
+	return ev;
+}
+
+/* copies all events in this dive computer */
+void copy_events(struct divecomputer *s, struct divecomputer *d)
+{
+	struct event *ev, **pev;
+	if (!s || !d)
+		return;
+	ev = s->events;
+	pev = &d->events;
+	while (ev != NULL) {
+		struct event *new_ev = clone_event(ev);
+		*pev = new_ev;
+		pev = &new_ev->next;
+		ev = ev->next;
+	}
+	*pev = NULL;
+}
+
+int nr_cylinders(struct dive *dive)
+{
+	int nr;
+
+	for (nr = MAX_CYLINDERS; nr; --nr) {
+		cylinder_t *cylinder = dive->cylinder + nr - 1;
+		if (!cylinder_nodata(cylinder))
+			break;
+	}
+	return nr;
+}
+
+int nr_weightsystems(struct dive *dive)
+{
+	int nr;
+
+	for (nr = MAX_WEIGHTSYSTEMS; nr; --nr) {
+		weightsystem_t *ws = dive->weightsystem + nr - 1;
+		if (!weightsystem_none(ws))
+			break;
+	}
+	return nr;
+}
+
+/* copy the equipment data part of the cylinders */
+void copy_cylinders(struct dive *s, struct dive *d, bool used_only)
+{
+	int i,j;
+	if (!s || !d)
+		return;
+	for (i = 0; i < MAX_CYLINDERS; i++) {
+		free((void *)d->cylinder[i].type.description);
+		memset(&d->cylinder[i], 0, sizeof(cylinder_t));
+	}
+	for (i = j = 0; i < MAX_CYLINDERS; i++) {
+		if (!used_only || is_cylinder_used(s, i)) {
+			d->cylinder[j].type = s->cylinder[i].type;
+			d->cylinder[j].type.description = copy_string(s->cylinder[i].type.description);
+			d->cylinder[j].gasmix = s->cylinder[i].gasmix;
+			d->cylinder[j].depth = s->cylinder[i].depth;
+			d->cylinder[j].cylinder_use = s->cylinder[i].cylinder_use;
+			d->cylinder[j].manually_added = true;
+			j++;
+		}
+	}
+}
+
+int cylinderuse_from_text(const char *text)
+{
+	for (enum cylinderuse i = 0; i < NUM_GAS_USE; i++) {
+		if (same_string(text, cylinderuse_text[i]) || same_string(text, translate("gettextFromC", cylinderuse_text[i])))
+			return i;
+	}
+	return -1;
+}
+
+void copy_samples(struct divecomputer *s, struct divecomputer *d)
+{
+	/* instead of carefully copying them one by one and calling add_sample
+	 * over and over again, let's just copy the whole blob */
+	if (!s || !d)
+		return;
+	int nr = s->samples;
+	d->samples = nr;
+	d->alloc_samples = nr;
+	// We expect to be able to read the memory in the other end of the pointer
+	// if its a valid pointer, so don't expect malloc() to return NULL for
+	// zero-sized malloc, do it ourselves.
+	d->sample = NULL;
+
+	if(!nr)
+		return;
+
+	d->sample = malloc(nr * sizeof(struct sample));
+	if (d->sample)
+		memcpy(d->sample, s->sample, nr * sizeof(struct sample));
+}
+
+struct sample *prepare_sample(struct divecomputer *dc)
+{
+	if (dc) {
+		int nr = dc->samples;
+		int alloc_samples = dc->alloc_samples;
+		struct sample *sample;
+		if (nr >= alloc_samples) {
+			struct sample *newsamples;
+
+			alloc_samples = (alloc_samples * 3) / 2 + 10;
+			newsamples = realloc(dc->sample, alloc_samples * sizeof(struct sample));
+			if (!newsamples)
+				return NULL;
+			dc->alloc_samples = alloc_samples;
+			dc->sample = newsamples;
+		}
+		sample = dc->sample + nr;
+		memset(sample, 0, sizeof(*sample));
+		return sample;
+	}
+	return NULL;
+}
+
+void finish_sample(struct divecomputer *dc)
+{
+	dc->samples++;
+}
+
+/*
+ * So when we re-calculate maxdepth and meandepth, we will
+ * not override the old numbers if they are close to the
+ * new ones.
+ *
+ * Why? Because a dive computer may well actually track the
+ * max depth and mean depth at finer granularity than the
+ * samples it stores. So it's possible that the max and mean
+ * have been reported more correctly originally.
+ *
+ * Only if the values calculated from the samples are clearly
+ * different do we override the normal depth values.
+ *
+ * This considers 1m to be "clearly different". That's
+ * a totally random number.
+ */
+static void update_depth(depth_t *depth, int new)
+{
+	if (new) {
+		int old = depth->mm;
+
+		if (abs(old - new) > 1000)
+			depth->mm = new;
+	}
+}
+
+static void update_temperature(temperature_t *temperature, int new)
+{
+	if (new) {
+		int old = temperature->mkelvin;
+
+		if (abs(old - new) > 1000)
+			temperature->mkelvin = new;
+	}
+}
+
+/*
+ * Calculate how long we were actually under water, and the average
+ * depth while under water.
+ *
+ * This ignores any surface time in the middle of the dive.
+ */
+void fixup_dc_duration(struct divecomputer *dc)
+{
+	int duration, i;
+	int lasttime, lastdepth, depthtime;
+
+	duration = 0;
+	lasttime = 0;
+	lastdepth = 0;
+	depthtime = 0;
+	for (i = 0; i < dc->samples; i++) {
+		struct sample *sample = dc->sample + i;
+		int time = sample->time.seconds;
+		int depth = sample->depth.mm;
+
+		/* We ignore segments at the surface */
+		if (depth > SURFACE_THRESHOLD || lastdepth > SURFACE_THRESHOLD) {
+			duration += time - lasttime;
+			depthtime += (time - lasttime) * (depth + lastdepth) / 2;
+		}
+		lastdepth = depth;
+		lasttime = time;
+	}
+	if (duration) {
+		dc->duration.seconds = duration;
+		dc->meandepth.mm = (depthtime + duration / 2) / duration;
+	}
+}
+
+void per_cylinder_mean_depth(struct dive *dive, struct divecomputer *dc, int *mean, int *duration)
+{
+	int i;
+	int depthtime[MAX_CYLINDERS] = { 0, };
+	uint32_t lasttime = 0;
+	int lastdepth = 0;
+	int idx = 0;
+
+	for (i = 0; i < MAX_CYLINDERS; i++)
+		mean[i] = duration[i] = 0;
+	if (!dc)
+		return;
+	struct event *ev = get_next_event(dc->events, "gaschange");
+	if (!ev || (dc && dc->sample && ev->time.seconds == dc->sample[0].time.seconds && get_next_event(ev->next, "gaschange") == NULL)) {
+		// we have either no gas change or only one gas change and that's setting an explicit first cylinder
+		mean[explicit_first_cylinder(dive, dc)] = dc->meandepth.mm;
+		duration[explicit_first_cylinder(dive, dc)] = dc->duration.seconds;
+
+		if (dc->divemode == CCR) {
+			// Do the same for the  O2 cylinder
+			int o2_cyl = get_cylinder_idx_by_use(dive, OXYGEN);
+			if (o2_cyl < 0)
+				return;
+			mean[o2_cyl] = dc->meandepth.mm;
+			duration[o2_cyl] = dc->duration.seconds;
+		}
+		return;
+	}
+	if (!dc->samples)
+		dc = fake_dc(dc, false);
+	for (i = 0; i < dc->samples; i++) {
+		struct sample *sample = dc->sample + i;
+		uint32_t time = sample->time.seconds;
+		int depth = sample->depth.mm;
+
+		/* Make sure to move the event past 'lasttime' */
+		while (ev && lasttime >= ev->time.seconds) {
+			idx = get_cylinder_index(dive, ev);
+			ev = get_next_event(ev->next, "gaschange");
+		}
+
+		/* Do we need to fake a midway sample at an event? */
+		if (ev && time > ev->time.seconds) {
+			int newtime = ev->time.seconds;
+			int newdepth = interpolate(lastdepth, depth, newtime - lasttime, time - lasttime);
+
+			time = newtime;
+			depth = newdepth;
+			i--;
+		}
+		/* We ignore segments at the surface */
+		if (depth > SURFACE_THRESHOLD || lastdepth > SURFACE_THRESHOLD) {
+			duration[idx] += time - lasttime;
+			depthtime[idx] += (time - lasttime) * (depth + lastdepth) / 2;
+		}
+		lastdepth = depth;
+		lasttime = time;
+	}
+	for (i = 0; i < MAX_CYLINDERS; i++) {
+		if (duration[i])
+			mean[i] = (depthtime[i] + duration[i] / 2) / duration[i];
+	}
+}
+
+static void update_min_max_temperatures(struct dive *dive, temperature_t temperature)
+{
+	if (temperature.mkelvin) {
+		if (!dive->maxtemp.mkelvin || temperature.mkelvin > dive->maxtemp.mkelvin)
+			dive->maxtemp = temperature;
+		if (!dive->mintemp.mkelvin || temperature.mkelvin < dive->mintemp.mkelvin)
+			dive->mintemp = temperature;
+	}
+}
+
+int gas_volume(cylinder_t *cyl, pressure_t p)
+{
+	double bar = p.mbar / 1000.0;
+	double z_factor = gas_compressibility_factor(&cyl->gasmix, bar);
+	return cyl->type.size.mliter * bar_to_atm(bar) / z_factor;
+}
+
+/*
+ * If the cylinder tank pressures are within half a bar
+ * (about 8 PSI) of the sample pressures, we consider it
+ * to be a rounding error, and throw them away as redundant.
+ */
+static int same_rounded_pressure(pressure_t a, pressure_t b)
+{
+	return abs(a.mbar - b.mbar) <= 500;
+}
+
+/* Some dive computers (Cobalt) don't start the dive with cylinder 0 but explicitly
+ * tell us what the first gas is with a gas change event in the first sample.
+ * Sneakily we'll use a return value of 0 (or FALSE) when there is no explicit
+ * first cylinder - in which case cylinder 0 is indeed the first cylinder */
+int explicit_first_cylinder(struct dive *dive, struct divecomputer *dc)
+{
+	if (dc) {
+		struct event *ev = get_next_event(dc->events, "gaschange");
+		if (ev && dc->sample && ev->time.seconds == dc->sample[0].time.seconds)
+			return get_cylinder_index(dive, ev);
+		else if (dc->divemode == CCR)
+			return MAX(get_cylinder_idx_by_use(dive, DILUENT), 0);
+	}
+	return 0;
+}
+
+/* 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)
+{
+	struct event *ev;
+	int new_setpoint = 0;
+
+	if (dc->divemode == CCR)
+		new_setpoint = prefs.defaultsetpoint;
+
+	if (dc->divemode == OC &&
+	    (same_string(dc->model, "Shearwater Predator") ||
+	     same_string(dc->model, "Shearwater Petrel") ||
+	     same_string(dc->model, "Shearwater Nerd"))) {
+		// make sure there's no setpoint in the samples
+		// this is an irreversible change - so switching a dive to OC
+		// by mistake when it's actually CCR is _bad_
+		// 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 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);
+				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);
+			if (abs(dc->sample[i].setpoint.mbar - (int)(1000 * pressures.o2)) <= 50)
+				dc->sample[i].setpoint.mbar = 0;
+		}
+	}
+
+	// an "SP change" event at t=0 is currently our marker for OC vs CCR
+	// this will need to change to a saner setup, but for now we can just
+	// check if such an event is there and adjust it, or add that event
+	ev = get_next_event(dc->events, "SP change");
+	if (ev && ev->time.seconds == 0) {
+		ev->value = new_setpoint;
+	} else {
+		if (!add_event(dc, 0, SAMPLE_EVENT_PO2, 0, new_setpoint, "SP change"))
+			fprintf(stderr, "Could not add setpoint change event\n");
+	}
+}
+
+void sanitize_gasmix(struct gasmix *mix)
+{
+	unsigned int o2, he;
+
+	o2 = mix->o2.permille;
+	he = mix->he.permille;
+
+	/* Regular air: leave empty */
+	if (!he) {
+		if (!o2)
+			return;
+		/* 20.8% to 21% O2 is just air */
+		if (gasmix_is_air(mix)) {
+			mix->o2.permille = 0;
+			return;
+		}
+	}
+
+	/* Sane mix? */
+	if (o2 <= 1000 && he <= 1000 && o2 + he <= 1000)
+		return;
+	fprintf(stderr, "Odd gasmix: %u O2 %u He\n", o2, he);
+	memset(mix, 0, sizeof(*mix));
+}
+
+/*
+ * See if the size/workingpressure looks like some standard cylinder
+ * size, eg "AL80".
+ *
+ * NOTE! We don't take compressibility into account when naming
+ * cylinders. That makes a certain amount of sense, since the
+ * cylinder name is independent from the gasmix, and different
+ * gasmixes have different compressibility.
+ */
+static void match_standard_cylinder(cylinder_type_t *type)
+{
+	double cuft, bar;
+	int psi, len;
+	const char *fmt;
+	char buffer[40], *p;
+
+	/* Do we already have a cylinder description? */
+	if (type->description)
+		return;
+
+	bar = type->workingpressure.mbar / 1000.0;
+	cuft = ml_to_cuft(type->size.mliter);
+	cuft *= bar_to_atm(bar);
+	psi = to_PSI(type->workingpressure);
+
+	switch (psi) {
+	case 2300 ... 2500: /* 2400 psi: LP tank */
+		fmt = "LP%d";
+		break;
+	case 2600 ... 2700: /* 2640 psi: LP+10% */
+		fmt = "LP%d";
+		break;
+	case 2900 ... 3100: /* 3000 psi: ALx tank */
+		fmt = "AL%d";
+		break;
+	case 3400 ... 3500: /* 3442 psi: HP tank */
+		fmt = "HP%d";
+		break;
+	case 3700 ... 3850: /* HP+10% */
+		fmt = "HP%d+";
+		break;
+	default:
+		return;
+	}
+	len = snprintf(buffer, sizeof(buffer), fmt, (int)rint(cuft));
+	p = malloc(len + 1);
+	if (!p)
+		return;
+	memcpy(p, buffer, len + 1);
+	type->description = p;
+}
+
+
+/*
+ * There are two ways to give cylinder size information:
+ *  - total amount of gas in cuft (depends on working pressure and physical size)
+ *  - physical size
+ *
+ * where "physical size" is the one that actually matters and is sane.
+ *
+ * We internally use physical size only. But we save the workingpressure
+ * so that we can do the conversion if required.
+ */
+static void sanitize_cylinder_type(cylinder_type_t *type)
+{
+	double volume_of_air, volume;
+
+	/* If we have no working pressure, it had *better* be just a physical size! */
+	if (!type->workingpressure.mbar)
+		return;
+
+	/* No size either? Nothing to go on */
+	if (!type->size.mliter)
+		return;
+
+	if (xml_parsing_units.volume == CUFT) {
+		double bar = type->workingpressure.mbar / 1000.0;
+		/* confusing - we don't really start from ml but millicuft !*/
+		volume_of_air = cuft_to_l(type->size.mliter);
+		/* milliliters at 1 atm: not corrected for compressibility! */
+		volume = volume_of_air / bar_to_atm(bar);
+		type->size.mliter = rint(volume);
+	}
+
+	/* Ok, we have both size and pressure: try to match a description */
+	match_standard_cylinder(type);
+}
+
+static void sanitize_cylinder_info(struct dive *dive)
+{
+	int i;
+
+	for (i = 0; i < MAX_CYLINDERS; i++) {
+		sanitize_gasmix(&dive->cylinder[i].gasmix);
+		sanitize_cylinder_type(&dive->cylinder[i].type);
+	}
+}
+
+/* some events should never be thrown away */
+static bool is_potentially_redundant(struct event *event)
+{
+	if (!strcmp(event->name, "gaschange"))
+		return false;
+	if (!strcmp(event->name, "bookmark"))
+		return false;
+	if (!strcmp(event->name, "heading"))
+		return false;
+	return true;
+}
+
+/* match just by name - we compare the details in the code that uses this helper */
+static struct event *find_previous_event(struct divecomputer *dc, struct event *event)
+{
+	struct event *ev = dc->events;
+	struct event *previous = NULL;
+
+	if (same_string(event->name, ""))
+		return NULL;
+	while (ev && ev != event) {
+		if (same_string(ev->name, event->name))
+			previous = ev;
+		ev = ev->next;
+	}
+	return previous;
+}
+
+static void fixup_surface_pressure(struct dive *dive)
+{
+	struct divecomputer *dc;
+	int sum = 0, nr = 0;
+
+	for_each_dc (dive, dc) {
+		if (dc->surface_pressure.mbar) {
+			sum += dc->surface_pressure.mbar;
+			nr++;
+		}
+	}
+	if (nr)
+		dive->surface_pressure.mbar = (sum + nr / 2) / nr;
+}
+
+static void fixup_water_salinity(struct dive *dive)
+{
+	struct divecomputer *dc;
+	int sum = 0, nr = 0;
+
+	for_each_dc (dive, dc) {
+		if (dc->salinity) {
+			if (dc->salinity < 500)
+				dc->salinity += FRESHWATER_SALINITY;
+			sum += dc->salinity;
+			nr++;
+		}
+	}
+	if (nr)
+		dive->salinity = (sum + nr / 2) / nr;
+}
+
+static void fixup_meandepth(struct dive *dive)
+{
+	struct divecomputer *dc;
+	int sum = 0, nr = 0;
+
+	for_each_dc (dive, dc) {
+		if (dc->meandepth.mm) {
+			sum += dc->meandepth.mm;
+			nr++;
+		}
+	}
+	if (nr)
+		dive->meandepth.mm = (sum + nr / 2) / nr;
+}
+
+static void fixup_duration(struct dive *dive)
+{
+	struct divecomputer *dc;
+	unsigned int duration = 0;
+
+	for_each_dc (dive, dc)
+		duration = MAX(duration, dc->duration.seconds);
+
+	dive->duration.seconds = duration;
+}
+
+/*
+ * What do the dive computers say the water temperature is?
+ * (not in the samples, but as dc property for dcs that support that)
+ */
+unsigned int dc_watertemp(struct divecomputer *dc)
+{
+	int sum = 0, nr = 0;
+
+	do {
+		if (dc->watertemp.mkelvin) {
+			sum += dc->watertemp.mkelvin;
+			nr++;
+		}
+	} while ((dc = dc->next) != NULL);
+	if (!nr)
+		return 0;
+	return (sum + nr / 2) / nr;
+}
+
+static void fixup_watertemp(struct dive *dive)
+{
+	if (!dive->watertemp.mkelvin)
+		dive->watertemp.mkelvin = dc_watertemp(&dive->dc);
+}
+
+/*
+ * What do the dive computers say the air temperature is?
+ */
+unsigned int dc_airtemp(struct divecomputer *dc)
+{
+	int sum = 0, nr = 0;
+
+	do {
+		if (dc->airtemp.mkelvin) {
+			sum += dc->airtemp.mkelvin;
+			nr++;
+		}
+	} while ((dc = dc->next) != NULL);
+	if (!nr)
+		return 0;
+	return (sum + nr / 2) / nr;
+}
+
+static void fixup_cylinder_use(struct dive *dive) // for CCR dives, store the indices
+{						  // of the oxygen and diluent cylinders
+	dive->oxygen_cylinder_index = get_cylinder_idx_by_use(dive, OXYGEN);
+	dive->diluent_cylinder_index = get_cylinder_idx_by_use(dive, DILUENT);
+}
+
+static void fixup_airtemp(struct dive *dive)
+{
+	if (!dive->airtemp.mkelvin)
+		dive->airtemp.mkelvin = dc_airtemp(&dive->dc);
+}
+
+/* zero out the airtemp in the dive structure if it was just created by
+ * running fixup on the dive. keep it if it had been edited by hand */
+static void un_fixup_airtemp(struct dive *a)
+{
+	if (a->airtemp.mkelvin && a->airtemp.mkelvin == dc_airtemp(&a->dc))
+		a->airtemp.mkelvin = 0;
+}
+
+/*
+ * events are stored as a linked list, so the concept of
+ * "consecutive, identical events" is somewhat hard to
+ * implement correctly (especially given that on some dive
+ * computers events are asynchronous, so they can come in
+ * between what would be the non-constant sample rate).
+ *
+ * So what we do is that we throw away clearly redundant
+ * events that are fewer than 61 seconds apart (assuming there
+ * is no dive computer with a sample rate of more than 60
+ * seconds... that would be pretty pointless to plot the
+ * profile with)
+ *
+ * We first only mark the events for deletion so that we
+ * still know when the previous event happened.
+ */
+static void fixup_dc_events(struct divecomputer *dc)
+{
+	struct event *event;
+
+	event = dc->events;
+	while (event) {
+		struct event *prev;
+		if (is_potentially_redundant(event)) {
+			prev = find_previous_event(dc, event);
+			if (prev && prev->value == event->value &&
+			    prev->flags == event->flags &&
+			    event->time.seconds - prev->time.seconds < 61)
+				event->deleted = true;
+		}
+		event = event->next;
+	}
+	event = dc->events;
+	while (event) {
+		if (event->next && event->next->deleted) {
+			struct event *nextnext = event->next->next;
+			free(event->next);
+			event->next = nextnext;
+		} else {
+			event = event->next;
+		}
+	}
+}
+
+static int interpolate_depth(struct divecomputer *dc, int idx, int lastdepth, int lasttime, int now)
+{
+	int i;
+	int nextdepth = lastdepth;
+	int nexttime = now;
+
+	for (i = idx+1; i < dc->samples; i++) {
+		struct sample *sample = dc->sample + i;
+		if (sample->depth.mm < 0)
+			continue;
+		nextdepth = sample->depth.mm;
+		nexttime = sample->time.seconds;
+		break;
+	}
+	return interpolate(lastdepth, nextdepth, now-lasttime, nexttime-lasttime);
+}
+
+static void fixup_dc_depths(struct dive *dive, struct divecomputer *dc)
+{
+	int i;
+	int maxdepth = dc->maxdepth.mm;
+	int lasttime = 0, lastdepth = 0;
+
+	for (i = 0; i < dc->samples; i++) {
+		struct sample *sample = dc->sample + i;
+		int time = sample->time.seconds;
+		int depth = sample->depth.mm;
+
+		if (depth < 0) {
+			depth = interpolate_depth(dc, i, lastdepth, lasttime, time);
+			sample->depth.mm = depth;
+		}
+
+		if (depth > SURFACE_THRESHOLD) {
+			if (depth > maxdepth)
+				maxdepth = depth;
+		}
+
+		lastdepth = depth;
+		lasttime = time;
+		if (sample->cns > dive->maxcns)
+			dive->maxcns = sample->cns;
+	}
+
+	update_depth(&dc->maxdepth, maxdepth);
+	if (maxdepth > dive->maxdepth.mm)
+		dive->maxdepth.mm = maxdepth;
+}
+
+static void fixup_dc_temp(struct dive *dive, struct divecomputer *dc)
+{
+	int i;
+	int mintemp = 0, lasttemp = 0;
+
+	for (i = 0; i < dc->samples; i++) {
+		struct sample *sample = dc->sample + i;
+		int temp = sample->temperature.mkelvin;
+
+		if (temp) {
+			/*
+			 * If we have consecutive identical
+			 * temperature readings, throw away
+			 * the redundant ones.
+			 */
+			if (lasttemp == temp)
+				sample->temperature.mkelvin = 0;
+			else
+				lasttemp = temp;
+
+			if (!mintemp || temp < mintemp)
+				mintemp = temp;
+		}
+
+		update_min_max_temperatures(dive, sample->temperature);
+	}
+	update_temperature(&dc->watertemp, mintemp);
+	update_min_max_temperatures(dive, dc->watertemp);
+}
+
+/*
+ * Fix up cylinder sensor information in the samples if we have
+ * an explicit first cylinder
+ */
+static void fixup_dc_cylinder_index(struct dive *dive, struct divecomputer *dc)
+{
+	int i;
+	int first_cylinder = explicit_first_cylinder(dive, dc);
+
+	if (!first_cylinder)
+		return;
+
+	for (i = 0; i < dc->samples; i++) {
+		struct sample *sample = dc->sample + i;
+
+		if (sample->sensor == 0)
+			sample->sensor = first_cylinder;
+	}
+}
+
+/*
+ * Simplify dc pressure information:
+ *  (a) Remove redundant pressure information
+ *  (b) Remove linearly interpolated pressure data
+ */
+static void simplify_dc_pressures(struct dive *dive, struct divecomputer *dc)
+{
+	int i, j;
+	int lastindex = -1;
+	int lastpressure = 0, lasto2pressure = 0;
+	int pressure_delta[MAX_CYLINDERS] = { INT_MAX, };
+
+	for (i = 0; i < dc->samples; i++) {
+		struct sample *sample = dc->sample + i;
+		int pressure = sample->cylinderpressure.mbar;
+		int o2_pressure = sample->o2cylinderpressure.mbar;
+		int index;
+
+		index = sample->sensor;
+
+		if (index == lastindex) {
+			/* Remove duplicate redundant pressure information */
+			if (pressure == lastpressure)
+				sample->cylinderpressure.mbar = 0;
+			if (o2_pressure == lasto2pressure)
+				sample->o2cylinderpressure.mbar = 0;
+			/* check for simply linear data in the samples
+			   +INT_MAX means uninitialized, -INT_MAX means not linear */
+			if (pressure_delta[index] != -INT_MAX && lastpressure) {
+				if (pressure_delta[index] == INT_MAX) {
+					pressure_delta[index] = abs(pressure - lastpressure);
+				} else {
+					int cur_delta = abs(pressure - lastpressure);
+					if (cur_delta && abs(cur_delta - pressure_delta[index]) > 150) {
+						/* ok the samples aren't just a linearisation
+						 * between start and end */
+						pressure_delta[index] = -INT_MAX;
+					}
+				}
+			}
+		}
+		lastindex = index;
+		lastpressure = pressure;
+		lasto2pressure = o2_pressure;
+	}
+
+	/* if all the samples for a cylinder have pressure data that
+	 * is basically equidistant throw out the sample cylinder pressure
+	 * information but make sure we still have a valid start and end
+	 * pressure
+	 * this happens when DivingLog decides to linearalize the
+	 * pressure between beginning and end and for strange reasons
+	 * decides to put that in the sample data as if it came from
+	 * the dive computer; we don't want that (we'll visualize with
+	 * constant SAC rate instead)
+	 * WARNING WARNING - I have only seen this in single tank dives
+	 * --- maybe I should try to create a multi tank dive and see what
+	 * --- divinglog does there - but the code right now is only tested
+	 * --- for the single tank case */
+	for (j = 0; j < MAX_CYLINDERS; j++) {
+		if (abs(pressure_delta[j]) != INT_MAX) {
+			cylinder_t *cyl = dive->cylinder + j;
+			for (i = 0; i < dc->samples; i++)
+				if (dc->sample[i].sensor == j)
+					dc->sample[i].cylinderpressure.mbar = 0;
+			if (!cyl->start.mbar)
+				cyl->start.mbar = cyl->sample_start.mbar;
+			if (!cyl->end.mbar)
+				cyl->end.mbar = cyl->sample_end.mbar;
+			cyl->sample_start.mbar = 0;
+			cyl->sample_end.mbar = 0;
+		}
+	}
+}
+
+/* FIXME! sensor -> cylinder mapping? */
+static void fixup_start_pressure(struct dive *dive, int idx, pressure_t p)
+{
+	if (idx >= 0 && idx < MAX_CYLINDERS) {
+		cylinder_t *cyl = dive->cylinder + idx;
+		if (p.mbar && !cyl->sample_start.mbar)
+			cyl->sample_start = p;
+	}
+}
+
+static void fixup_end_pressure(struct dive *dive, int idx, pressure_t p)
+{
+	if (idx >= 0 && idx < MAX_CYLINDERS) {
+		cylinder_t *cyl = dive->cylinder + idx;
+		if (p.mbar && !cyl->sample_end.mbar)
+			cyl->sample_end = p;
+	}
+}
+
+/*
+ * Check the cylinder pressure sample information and fill in the
+ * overall cylinder pressures from those.
+ *
+ * We ignore surface samples for tank pressure information.
+ *
+ * At the beginning of the dive, let the cylinder cool down
+ * if the diver starts off at the surface. And at the end
+ * of the dive, there may be surface pressures where the
+ * diver has already turned off the air supply (especially
+ * for computers like the Uemis Zurich that end up saving
+ * quite a bit of samples after the dive has ended).
+ */
+static void fixup_dive_pressures(struct dive *dive, struct divecomputer *dc)
+{
+	int i, o2index = -1;
+
+	if (dive->dc.divemode == CCR)
+		o2index = get_cylinder_idx_by_use(dive, OXYGEN);
+
+	/* Walk the samples from the beginning to find starting pressures.. */
+	for (i = 0; i < dc->samples; i++) {
+		struct sample *sample = dc->sample + i;
+
+		if (sample->depth.mm < SURFACE_THRESHOLD)
+			continue;
+
+		fixup_start_pressure(dive, sample->sensor, sample->cylinderpressure);
+		fixup_start_pressure(dive, o2index, sample->o2cylinderpressure);
+	}
+
+	/* ..and from the end for ending pressures */
+	for (i = dc->samples; --i >= 0; ) {
+		struct sample *sample = dc->sample + i;
+
+		if (sample->depth.mm < SURFACE_THRESHOLD)
+			continue;
+
+		fixup_end_pressure(dive, sample->sensor, sample->cylinderpressure);
+		fixup_end_pressure(dive, o2index, sample->o2cylinderpressure);
+	}
+
+	simplify_dc_pressures(dive, dc);
+}
+
+static void fixup_dive_dc(struct dive *dive, struct divecomputer *dc)
+{
+	int i;
+
+	/* Add device information to table */
+	if (dc->deviceid && (dc->serial || dc->fw_version))
+		create_device_node(dc->model, dc->deviceid, dc->serial, dc->fw_version, "");
+
+	/* Fixup duration and mean depth */
+	fixup_dc_duration(dc);
+
+	/* Fix up sample depth data */
+	fixup_dc_depths(dive, dc);
+
+	/* Fix up dive temperatures based on dive computer samples */
+	fixup_dc_temp(dive, dc);
+
+	/* Fix up cylinder sensor data */
+	fixup_dc_cylinder_index(dive, dc);
+
+	/* Fix up cylinder pressures based on DC info */
+	fixup_dive_pressures(dive, dc);
+
+	fixup_dc_events(dc);
+}
+
+struct dive *fixup_dive(struct dive *dive)
+{
+	int i;
+	struct divecomputer *dc;
+
+	sanitize_cylinder_info(dive);
+	dive->maxcns = dive->cns;
+
+	/*
+	 * Use the dive's temperatures for minimum and maximum in case
+	 * we do not have temperatures recorded by DC.
+	 */
+
+	update_min_max_temperatures(dive, dive->watertemp);
+
+	for_each_dc (dive, dc)
+		fixup_dive_dc(dive, dc);
+
+	fixup_water_salinity(dive);
+	fixup_surface_pressure(dive);
+	fixup_meandepth(dive);
+	fixup_duration(dive);
+	fixup_watertemp(dive);
+	fixup_airtemp(dive);
+	fixup_cylinder_use(dive); // store indices for CCR oxygen and diluent cylinders
+	for (i = 0; i < MAX_CYLINDERS; i++) {
+		cylinder_t *cyl = dive->cylinder + i;
+		add_cylinder_description(&cyl->type);
+		if (same_rounded_pressure(cyl->sample_start, cyl->start))
+			cyl->start.mbar = 0;
+		if (same_rounded_pressure(cyl->sample_end, cyl->end))
+			cyl->end.mbar = 0;
+	}
+	update_cylinder_related_info(dive);
+	for (i = 0; i < MAX_WEIGHTSYSTEMS; i++) {
+		weightsystem_t *ws = dive->weightsystem + i;
+		add_weightsystem_description(ws);
+	}
+	/* we should always have a uniq ID as that gets assigned during alloc_dive(),
+	 * but we want to make sure... */
+	if (!dive->id)
+		dive->id = dive_getUniqID(dive);
+
+	return dive;
+}
+
+/* Don't pick a zero for MERGE_MIN() */
+#define MERGE_MAX(res, a, b, n) res->n = MAX(a->n, b->n)
+#define MERGE_MIN(res, a, b, n) res->n = (a->n) ? (b->n) ? MIN(a->n, b->n) : (a->n) : (b->n)
+#define MERGE_TXT(res, a, b, n) res->n = merge_text(a->n, b->n)
+#define MERGE_NONZERO(res, a, b, n) res->n = a->n ? a->n : b->n
+
+struct sample *add_sample(struct sample *sample, int time, struct divecomputer *dc)
+{
+	struct sample *p = prepare_sample(dc);
+
+	if (p) {
+		*p = *sample;
+		p->time.seconds = time;
+		finish_sample(dc);
+	}
+	return p;
+}
+
+/*
+ * This is like add_sample(), but if the distance from the last sample
+ * is excessive, we add two surface samples in between.
+ *
+ * This is so that if you merge two non-overlapping dives, we make sure
+ * that the time in between the dives is at the surface, not some "last
+ * sample that happened to be at a depth of 1.2m".
+ */
+static void merge_one_sample(struct sample *sample, int time, struct divecomputer *dc)
+{
+	int last = dc->samples - 1;
+	if (last >= 0) {
+		static struct sample surface;
+		struct sample *prev = dc->sample + last;
+		int last_time = prev->time.seconds;
+		int last_depth = prev->depth.mm;
+
+		/*
+		 * Only do surface events if the samples are more than
+		 * a minute apart, and shallower than 5m
+		 */
+		if (time > last_time + 60 && last_depth < 5000) {
+			add_sample(&surface, last_time + 20, dc);
+			add_sample(&surface, time - 20, dc);
+		}
+	}
+	add_sample(sample, time, dc);
+}
+
+
+/*
+ * Merge samples. Dive 'a' is "offset" seconds before Dive 'b'
+ */
+static void merge_samples(struct divecomputer *res, struct divecomputer *a, struct divecomputer *b, int offset)
+{
+	int asamples = a->samples;
+	int bsamples = b->samples;
+	struct sample *as = a->sample;
+	struct sample *bs = b->sample;
+
+	/*
+	 * We want a positive sample offset, so that sample
+	 * times are always positive. So if the samples for
+	 * 'b' are before the samples for 'a' (so the offset
+	 * is negative), we switch a and b around, and use
+	 * the reverse offset.
+	 */
+	if (offset < 0) {
+		offset = -offset;
+		asamples = bsamples;
+		bsamples = a->samples;
+		as = bs;
+		bs = a->sample;
+	}
+
+	for (;;) {
+		int at, bt;
+		struct sample sample;
+
+		if (!res)
+			return;
+
+		at = asamples ? as->time.seconds : -1;
+		bt = bsamples ? bs->time.seconds + offset : -1;
+
+		/* No samples? All done! */
+		if (at < 0 && bt < 0)
+			return;
+
+		/* Only samples from a? */
+		if (bt < 0) {
+		add_sample_a:
+			merge_one_sample(as, at, res);
+			as++;
+			asamples--;
+			continue;
+		}
+
+		/* Only samples from b? */
+		if (at < 0) {
+		add_sample_b:
+			merge_one_sample(bs, bt, res);
+			bs++;
+			bsamples--;
+			continue;
+		}
+
+		if (at < bt)
+			goto add_sample_a;
+		if (at > bt)
+			goto add_sample_b;
+
+		/* same-time sample: add a merged sample. Take the non-zero ones */
+		sample = *bs;
+		if (as->depth.mm)
+			sample.depth = as->depth;
+		if (as->temperature.mkelvin)
+			sample.temperature = as->temperature;
+		if (as->cylinderpressure.mbar)
+			sample.cylinderpressure = as->cylinderpressure;
+		if (as->sensor)
+			sample.sensor = as->sensor;
+		if (as->cns)
+			sample.cns = as->cns;
+		if (as->setpoint.mbar)
+			sample.setpoint = as->setpoint;
+		if (as->ndl.seconds)
+			sample.ndl = as->ndl;
+		if (as->stoptime.seconds)
+			sample.stoptime = as->stoptime;
+		if (as->stopdepth.mm)
+			sample.stopdepth = as->stopdepth;
+		if (as->in_deco)
+			sample.in_deco = true;
+
+		merge_one_sample(&sample, at, res);
+
+		as++;
+		bs++;
+		asamples--;
+		bsamples--;
+	}
+}
+
+static char *merge_text(const char *a, const char *b)
+{
+	char *res;
+	if (!a && !b)
+		return NULL;
+	if (!a || !*a)
+		return copy_string(b);
+	if (!b || !*b)
+		return strdup(a);
+	if (!strcmp(a, b))
+		return copy_string(a);
+	res = malloc(strlen(a) + strlen(b) + 32);
+	if (!res)
+		return (char *)a;
+	sprintf(res, translate("gettextFromC", "(%s) or (%s)"), a, b);
+	return res;
+}
+
+#define SORT(a, b, field)         \
+	if (a->field != b->field) \
+		return a->field < b->field ? -1 : 1
+
+static int sort_event(struct event *a, struct event *b)
+{
+	SORT(a, b, time.seconds);
+	SORT(a, b, type);
+	SORT(a, b, flags);
+	SORT(a, b, value);
+	return strcmp(a->name, b->name);
+}
+
+static void merge_events(struct divecomputer *res, struct divecomputer *src1, struct divecomputer *src2, int offset)
+{
+	struct event *a, *b;
+	struct event **p = &res->events;
+
+	/* Always use positive offsets */
+	if (offset < 0) {
+		struct divecomputer *tmp;
+
+		offset = -offset;
+		tmp = src1;
+		src1 = src2;
+		src2 = tmp;
+	}
+
+	a = src1->events;
+	b = src2->events;
+	while (b) {
+		b->time.seconds += offset;
+		b = b->next;
+	}
+	b = src2->events;
+
+	while (a || b) {
+		int s;
+		if (!b) {
+			*p = a;
+			break;
+		}
+		if (!a) {
+			*p = b;
+			break;
+		}
+		s = sort_event(a, b);
+		/* Pick b */
+		if (s > 0) {
+			*p = b;
+			p = &b->next;
+			b = b->next;
+			continue;
+		}
+		/* Pick 'a' or neither */
+		if (s < 0) {
+			*p = a;
+			p = &a->next;
+		}
+		a = a->next;
+		continue;
+	}
+}
+
+/* Pick whichever has any info (if either). Prefer 'a' */
+static void merge_cylinder_type(cylinder_type_t *src, cylinder_type_t *dst)
+{
+	if (!dst->size.mliter)
+		dst->size.mliter = src->size.mliter;
+	if (!dst->workingpressure.mbar)
+		dst->workingpressure.mbar = src->workingpressure.mbar;
+	if (!dst->description) {
+		dst->description = src->description;
+		src->description = NULL;
+	}
+}
+
+static void merge_cylinder_mix(struct gasmix *src, struct gasmix *dst)
+{
+	if (!dst->o2.permille)
+		*dst = *src;
+}
+
+static void merge_cylinder_info(cylinder_t *src, cylinder_t *dst)
+{
+	merge_cylinder_type(&src->type, &dst->type);
+	merge_cylinder_mix(&src->gasmix, &dst->gasmix);
+	MERGE_MAX(dst, dst, src, start.mbar);
+	MERGE_MIN(dst, dst, src, end.mbar);
+}
+
+static void merge_weightsystem_info(weightsystem_t *res, weightsystem_t *a, weightsystem_t *b)
+{
+	if (!a->weight.grams)
+		a = b;
+	*res = *a;
+}
+
+/* get_cylinder_idx_by_use(): Find the index of the first cylinder with a particular CCR use type.
+ * The index returned corresponds to that of the first cylinder with a cylinder_use that
+ * equals the appropriate enum value [oxygen, diluent, bailout] given by cylinder_use_type.
+ * A negative number returned indicates that a match could not be found.
+ * Call parameters: dive = the dive being processed
+ *                  cylinder_use_type = an enum, one of {oxygen, diluent, bailout} */
+extern int get_cylinder_idx_by_use(struct dive *dive, enum cylinderuse cylinder_use_type)
+{
+	int cylinder_index;
+	for (cylinder_index = 0; cylinder_index < MAX_CYLINDERS; cylinder_index++) {
+		if (dive->cylinder[cylinder_index].cylinder_use == cylinder_use_type)
+			return cylinder_index; // return the index of the cylinder with that cylinder use type
+	}
+	return -1; // negative number means cylinder_use_type not found in list of cylinders
+}
+
+int gasmix_distance(const struct gasmix *a, const struct gasmix *b)
+{
+	int a_o2 = get_o2(a), b_o2 = get_o2(b);
+	int a_he = get_he(a), b_he = get_he(b);
+	int delta_o2 = a_o2 - b_o2, delta_he = a_he - b_he;
+
+	delta_he = delta_he * delta_he;
+	delta_o2 = delta_o2 * delta_o2;
+	return delta_he + delta_o2;
+}
+
+/* fill_pressures(): Compute partial gas pressures in bar from gasmix and ambient pressures, possibly for OC or CCR, to be
+ * extended to PSCT. This function does the calculations of gas pressures applicable to a single point on the dive profile.
+ * The structure "pressures" is used to return calculated gas pressures to the calling software.
+ * Call parameters:	po2 = po2 value applicable to the record in calling function
+ *			amb_pressure = ambient pressure applicable to the record in calling function
+ *			*pressures = structure for communicating o2 sensor values from and gas pressures to the calling function.
+ *			*mix = structure containing cylinder gas mixture information.
+ * This function called by: calculate_gas_information_new() in profile.c; add_segment() in deco.c.
+ */
+extern void fill_pressures(struct gas_pressures *pressures, const double amb_pressure, const struct gasmix *mix, double po2, enum dive_comp_type divemode)
+{
+	if (po2) {	// This is probably a CCR dive where pressures->o2 is defined
+		if (po2 >= amb_pressure) {
+			pressures->o2 = amb_pressure;
+			pressures->n2 = pressures->he = 0.0;
+		} else {
+			pressures->o2 = po2;
+			if (get_o2(mix) == 1000) {
+				pressures->he = pressures->n2 = 0;
+			} else {
+				pressures->he = (amb_pressure - pressures->o2) * (double)get_he(mix) / (1000 - get_o2(mix));
+				pressures->n2 = amb_pressure - pressures->o2 - pressures->he;
+			}
+		}
+	} else {
+		if (divemode == PSCR) { /* The steady state approximation should be good enough */
+			pressures->o2 = get_o2(mix) / 1000.0 * amb_pressure - (1.0 - get_o2(mix) / 1000.0) * prefs.o2consumption / (prefs.bottomsac * prefs.pscr_ratio / 1000.0);
+			if (pressures->o2 < 0) // He's dead, Jim.
+				pressures->o2 = 0;
+			if (get_o2(mix) != 1000) {
+				pressures->he = (amb_pressure - pressures->o2) * get_he(mix) / (1000.0 - get_o2(mix));
+				pressures->n2 = (amb_pressure - pressures->o2) * (1000 - get_o2(mix) - get_he(mix)) / (1000.0 - get_o2(mix));
+			} else {
+				pressures->he = pressures->n2 = 0;
+			}
+		} else {
+			// Open circuit dives: no gas pressure values available, they need to be calculated
+			pressures->o2 = get_o2(mix) / 1000.0 * amb_pressure; // These calculations are also used if the CCR calculation above..
+			pressures->he = get_he(mix) / 1000.0 * amb_pressure; // ..returned a po2 of zero (i.e. o2 sensor data not resolvable)
+			pressures->n2 = (1000 - get_o2(mix) - get_he(mix)) / 1000.0 * amb_pressure;
+		}
+	}
+}
+
+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;
+}
+
+/* Force an initial gaschange event to the (old) gas #0 */
+static void add_initial_gaschange(struct dive *dive, struct divecomputer *dc)
+{
+	struct event *ev = get_next_event(dc->events, "gaschange");
+
+	if (ev && ev->time.seconds < 30)
+		return;
+
+	/* Old starting gas mix */
+	add_gas_switch_event(dive, dc, 0, 0);
+}
+
+void dc_cylinder_renumber(struct dive *dive, struct divecomputer *dc, int mapping[])
+{
+	int i;
+	struct event *ev;
+
+	/* Did the first gas get remapped? Add gas switch event */
+	if (mapping[0] > 0)
+		add_initial_gaschange(dive, dc);
+
+	/* Remap the sensor indexes */
+	for (i = 0; i < dc->samples; i++) {
+		struct sample *s = dc->sample + i;
+		int sensor;
+
+		if (!s->cylinderpressure.mbar)
+			continue;
+		sensor = mapping[s->sensor];
+		if (sensor >= 0)
+			s->sensor = sensor;
+	}
+
+	/* Remap the gas change indexes */
+	for (ev = dc->events; ev; ev = ev->next) {
+		if (!event_is_gaschange(ev))
+			continue;
+		if (ev->gas.index < 0)
+			continue;
+		ev->gas.index = mapping[ev->gas.index];
+	}
+}
+
+/*
+ * If the cylinder indexes change (due to merging dives or deleting
+ * cylinders in the middle), we need to change the indexes in the
+ * dive computer data for this dive.
+ *
+ * Also note that we assume that the initial cylinder is cylinder 0,
+ * so if that got renamed, we need to create a fake gas change event
+ */
+static void cylinder_renumber(struct dive *dive, int mapping[])
+{
+	struct divecomputer *dc;
+	for_each_dc (dive, dc)
+		dc_cylinder_renumber(dive, dc, mapping);
+}
+
+/*
+ * Merging cylinder information is non-trivial, because the two dive computers
+ * may have different ideas of what the different cylinder indexing is.
+ *
+ * Logic: take all the cylinder information from the preferred dive ('a'), and
+ * then try to match each of the cylinders in the other dive by the gasmix that
+ * is the best match and hasn't been used yet.
+ */
+static void merge_cylinders(struct dive *res, struct dive *a, struct dive *b)
+{
+	int i, renumber = 0;
+	int mapping[MAX_CYLINDERS];
+	unsigned int used = 0;
+
+	/* Copy the cylinder info raw from 'a' */
+	memcpy(res->cylinder, a->cylinder, sizeof(res->cylinder));
+	memset(a->cylinder, 0, sizeof(a->cylinder));
+
+	for (i = 0; i < MAX_CYLINDERS; i++) {
+		int j;
+		cylinder_t *cyl = b->cylinder + i;
+
+		j = find_cylinder_match(cyl, res->cylinder, used);
+		mapping[i] = j;
+		if (j < 0)
+			continue;
+		used |= 1 << j;
+		merge_cylinder_info(cyl, res->cylinder + j);
+
+		/* If that renumbered the cylinders, fix it up! */
+		if (i != j)
+			renumber = 1;
+	}
+	if (renumber)
+		cylinder_renumber(b, mapping);
+}
+
+static void merge_equipment(struct dive *res, struct dive *a, struct dive *b)
+{
+	int i;
+
+	merge_cylinders(res, a, b);
+	for (i = 0; i < MAX_WEIGHTSYSTEMS; i++)
+		merge_weightsystem_info(res->weightsystem + i, a->weightsystem + i, b->weightsystem + i);
+}
+
+static void merge_airtemps(struct dive *res, struct dive *a, struct dive *b)
+{
+	un_fixup_airtemp(a);
+	un_fixup_airtemp(b);
+	MERGE_NONZERO(res, a, b, airtemp.mkelvin);
+}
+
+/*
+ * When merging two dives, this picks the trip from one, and removes it
+ * from the other.
+ *
+ * The 'next' dive is not involved in the dive merging, but is the dive
+ * that will be the next dive after the merged dive.
+ */
+static void pick_trip(struct dive *res, struct dive *pick)
+{
+	tripflag_t tripflag = pick->tripflag;
+	dive_trip_t *trip = pick->divetrip;
+
+	res->tripflag = tripflag;
+	add_dive_to_trip(res, trip);
+}
+
+/*
+ * Pick a trip for a dive
+ */
+static void merge_trip(struct dive *res, struct dive *a, struct dive *b)
+{
+	dive_trip_t *atrip, *btrip;
+
+	/*
+	 * The larger tripflag is more relevant: we prefer
+	 * take manually assigned trips over auto-generated
+	 * ones.
+	 */
+	if (a->tripflag > b->tripflag)
+		goto pick_a;
+
+	if (a->tripflag < b->tripflag)
+		goto pick_b;
+
+	/* Otherwise, look at the trip data and pick the "better" one */
+	atrip = a->divetrip;
+	btrip = b->divetrip;
+	if (!atrip)
+		goto pick_b;
+	if (!btrip)
+		goto pick_a;
+	if (!atrip->location)
+		goto pick_b;
+	if (!btrip->location)
+		goto pick_a;
+	if (!atrip->notes)
+		goto pick_b;
+	if (!btrip->notes)
+		goto pick_a;
+
+	/*
+	 * Ok, so both have location and notes.
+	 * Pick the earlier one.
+	 */
+	if (a->when < b->when)
+		goto pick_a;
+	goto pick_b;
+
+pick_a:
+	b = a;
+pick_b:
+	pick_trip(res, b);
+}
+
+#if CURRENTLY_NOT_USED
+/*
+ * Sample 's' is between samples 'a' and 'b'. It is 'offset' seconds before 'b'.
+ *
+ * If 's' and 'a' are at the same time, offset is 0, and b is NULL.
+ */
+static int compare_sample(struct sample *s, struct sample *a, struct sample *b, int offset)
+{
+	unsigned int depth = a->depth.mm;
+	int diff;
+
+	if (offset) {
+		unsigned int interval = b->time.seconds - a->time.seconds;
+		unsigned int depth_a = a->depth.mm;
+		unsigned int depth_b = b->depth.mm;
+
+		if (offset > interval)
+			return -1;
+
+		/* pick the average depth, scaled by the offset from 'b' */
+		depth = (depth_a * offset) + (depth_b * (interval - offset));
+		depth /= interval;
+	}
+	diff = s->depth.mm - depth;
+	if (diff < 0)
+		diff = -diff;
+	/* cut off at one meter difference */
+	if (diff > 1000)
+		diff = 1000;
+	return diff * diff;
+}
+
+/*
+ * Calculate a "difference" in samples between the two dives, given
+ * the offset in seconds between them. Use this to find the best
+ * match of samples between two different dive computers.
+ */
+static unsigned long sample_difference(struct divecomputer *a, struct divecomputer *b, int offset)
+{
+	int asamples = a->samples;
+	int bsamples = b->samples;
+	struct sample *as = a->sample;
+	struct sample *bs = b->sample;
+	unsigned long error = 0;
+	int start = -1;
+
+	if (!asamples || !bsamples)
+		return 0;
+
+	/*
+	 * skip the first sample - this way we know can always look at
+	 * as/bs[-1] to look at the samples around it in the loop.
+	 */
+	as++;
+	bs++;
+	asamples--;
+	bsamples--;
+
+	for (;;) {
+		int at, bt, diff;
+
+
+		/* If we run out of samples, punt */
+		if (!asamples)
+			return INT_MAX;
+		if (!bsamples)
+			return INT_MAX;
+
+		at = as->time.seconds;
+		bt = bs->time.seconds + offset;
+
+		/* b hasn't started yet? Ignore it */
+		if (bt < 0) {
+			bs++;
+			bsamples--;
+			continue;
+		}
+
+		if (at < bt) {
+			diff = compare_sample(as, bs - 1, bs, bt - at);
+			as++;
+			asamples--;
+		} else if (at > bt) {
+			diff = compare_sample(bs, as - 1, as, at - bt);
+			bs++;
+			bsamples--;
+		} else {
+			diff = compare_sample(as, bs, NULL, 0);
+			as++;
+			bs++;
+			asamples--;
+			bsamples--;
+		}
+
+		/* Invalid comparison point? */
+		if (diff < 0)
+			continue;
+
+		if (start < 0)
+			start = at;
+
+		error += diff;
+
+		if (at - start > 120)
+			break;
+	}
+	return error;
+}
+
+/*
+ * Dive 'a' is 'offset' seconds before dive 'b'
+ *
+ * This is *not* because the dive computers clocks aren't in sync,
+ * it is because the dive computers may "start" the dive at different
+ * points in the dive, so the sample at time X in dive 'a' is the
+ * same as the sample at time X+offset in dive 'b'.
+ *
+ * For example, some dive computers take longer to "wake up" when
+ * they sense that you are under water (ie Uemis Zurich if it was off
+ * when the dive started). And other dive computers have different
+ * depths that they activate at, etc etc.
+ *
+ * If we cannot find a shared offset, don't try to merge.
+ */
+static int find_sample_offset(struct divecomputer *a, struct divecomputer *b)
+{
+	int offset, best;
+	unsigned long max;
+
+	/* No samples? Merge at any time (0 offset) */
+	if (!a->samples)
+		return 0;
+	if (!b->samples)
+		return 0;
+
+	/*
+	 * Common special-case: merging a dive that came from
+	 * the same dive computer, so the samples are identical.
+	 * Check this first, without wasting time trying to find
+	 * some minimal offset case.
+	 */
+	best = 0;
+	max = sample_difference(a, b, 0);
+	if (!max)
+		return 0;
+
+	/*
+	 * Otherwise, look if we can find anything better within
+	 * a thirty second window..
+	 */
+	for (offset = -30; offset <= 30; offset++) {
+		unsigned long diff;
+
+		diff = sample_difference(a, b, offset);
+		if (diff > max)
+			continue;
+		best = offset;
+		max = diff;
+	}
+
+	return best;
+}
+#endif
+
+/*
+ * Are a and b "similar" values, when given a reasonable lower end expected
+ * difference?
+ *
+ * So for example, we'd expect different dive computers to give different
+ * max depth readings. You might have them on different arms, and they
+ * have different pressure sensors and possibly different ideas about
+ * water salinity etc.
+ *
+ * So have an expected minimum difference, but also allow a larger relative
+ * error value.
+ */
+static int similar(unsigned long a, unsigned long b, unsigned long expected)
+{
+	if (!a && !b)
+		return 1;
+
+	if (a && b) {
+		unsigned long min, max, diff;
+
+		min = a;
+		max = b;
+		if (a > b) {
+			min = b;
+			max = a;
+		}
+		diff = max - min;
+
+		/* Smaller than expected difference? */
+		if (diff < expected)
+			return 1;
+		/* Error less than 10% or the maximum */
+		if (diff * 10 < max)
+			return 1;
+	}
+	return 0;
+}
+
+/*
+ * Match two dive computer entries against each other, and
+ * tell if it's the same dive. Return 0 if "don't know",
+ * positive for "same dive" and negative for "definitely
+ * not the same dive"
+ */
+int match_one_dc(struct divecomputer *a, struct divecomputer *b)
+{
+	/* Not same model? Don't know if matching.. */
+	if (!a->model || !b->model)
+		return 0;
+	if (strcasecmp(a->model, b->model))
+		return 0;
+
+	/* Different device ID's? Don't know */
+	if (a->deviceid != b->deviceid)
+		return 0;
+
+	/* Do we have dive IDs? */
+	if (!a->diveid || !b->diveid)
+		return 0;
+
+	/*
+	 * If they have different dive ID's on the same
+	 * dive computer, that's a definite "same or not"
+	 */
+	return a->diveid == b->diveid ? 1 : -1;
+}
+
+/*
+ * Match every dive computer against each other to see if
+ * we have a matching dive.
+ *
+ * Return values:
+ *  -1 for "is definitely *NOT* the same dive"
+ *   0 for "don't know"
+ *   1 for "is definitely the same dive"
+ */
+static int match_dc_dive(struct divecomputer *a, struct divecomputer *b)
+{
+	do {
+		struct divecomputer *tmp = b;
+		do {
+			int match = match_one_dc(a, tmp);
+			if (match)
+				return match;
+			tmp = tmp->next;
+		} while (tmp);
+		a = a->next;
+	} while (a);
+	return 0;
+}
+
+static bool new_without_trip(struct dive *a)
+{
+	return a->downloaded && !a->divetrip;
+}
+
+/*
+ * Do we want to automatically try to merge two dives that
+ * look like they are the same dive?
+ *
+ * This happens quite commonly because you download a dive
+ * that you already had, or perhaps because you maintained
+ * multiple dive logs and want to load them all together
+ * (possibly one of them was imported from another dive log
+ * application entirely).
+ *
+ * NOTE! We mainly look at the dive time, but it can differ
+ * between two dives due to a few issues:
+ *
+ *  - rounding the dive date to the nearest minute in other dive
+ *    applications
+ *
+ *  - dive computers with "relative datestamps" (ie the dive
+ *    computer doesn't actually record an absolute date at all,
+ *    but instead at download-time synchronizes its internal
+ *    time with real-time on the downloading computer)
+ *
+ *  - using multiple dive computers with different real time on
+ *    the same dive
+ *
+ * We do not merge dives that look radically different, and if
+ * the dates are *too* far off the user will have to join two
+ * dives together manually. But this tries to handle the sane
+ * cases.
+ */
+static int likely_same_dive(struct dive *a, struct dive *b)
+{
+	int match, fuzz = 20 * 60;
+
+	/* don't merge manually added dives with anything */
+	if (same_string(a->dc.model, "manually added dive") ||
+	    same_string(b->dc.model, "manually added dive"))
+		return 0;
+
+	/* Don't try to merge dives with different trip information */
+	if (a->divetrip != b->divetrip) {
+		/*
+		 * Exception: if the dive is downloaded without any
+		 * explicit trip information, we do want to merge it
+		 * with existing old dives even if they have trips.
+		 */
+		if (!new_without_trip(a) && !new_without_trip(b))
+			return 0;
+	}
+
+	/*
+	 * Do some basic sanity testing of the values we
+	 * have filled in during 'fixup_dive()'
+	 */
+	if (!similar(a->maxdepth.mm, b->maxdepth.mm, 1000) ||
+	    (a->meandepth.mm && b->meandepth.mm && !similar(a->meandepth.mm, b->meandepth.mm, 1000)) ||
+	    !similar(a->duration.seconds, b->duration.seconds, 5 * 60))
+		return 0;
+
+	/* See if we can get an exact match on the dive computer */
+	match = match_dc_dive(&a->dc, &b->dc);
+	if (match)
+		return match > 0;
+
+	/*
+	 * Allow a time difference due to dive computer time
+	 * setting etc. Check if they overlap.
+	 */
+	fuzz = MAX(a->duration.seconds, b->duration.seconds) / 2;
+	if (fuzz < 60)
+		fuzz = 60;
+
+	return ((a->when <= b->when + fuzz) && (a->when >= b->when - fuzz));
+}
+
+/*
+ * This could do a lot more merging. Right now it really only
+ * merges almost exact duplicates - something that happens easily
+ * with overlapping dive downloads.
+ */
+struct dive *try_to_merge(struct dive *a, struct dive *b, bool prefer_downloaded)
+{
+	if (likely_same_dive(a, b))
+		return merge_dives(a, b, 0, prefer_downloaded);
+	return NULL;
+}
+
+void free_events(struct event *ev)
+{
+	while (ev) {
+		struct event *next = ev->next;
+		free(ev);
+		ev = next;
+	}
+}
+
+static void free_dc(struct divecomputer *dc)
+{
+	free(dc->sample);
+	free((void *)dc->model);
+	free_events(dc->events);
+	free(dc);
+}
+
+static void free_pic(struct picture *picture)
+{
+	if (picture) {
+		free(picture->filename);
+		free(picture);
+	}
+}
+
+static int same_sample(struct sample *a, struct sample *b)
+{
+	if (a->time.seconds != b->time.seconds)
+		return 0;
+	if (a->depth.mm != b->depth.mm)
+		return 0;
+	if (a->temperature.mkelvin != b->temperature.mkelvin)
+		return 0;
+	if (a->cylinderpressure.mbar != b->cylinderpressure.mbar)
+		return 0;
+	return a->sensor == b->sensor;
+}
+
+static int same_dc(struct divecomputer *a, struct divecomputer *b)
+{
+	int i;
+	struct event *eva, *evb;
+
+	i = match_one_dc(a, b);
+	if (i)
+		return i > 0;
+
+	if (a->when && b->when && a->when != b->when)
+		return 0;
+	if (a->samples != b->samples)
+		return 0;
+	for (i = 0; i < a->samples; i++)
+		if (!same_sample(a->sample + i, b->sample + i))
+			return 0;
+	eva = a->events;
+	evb = b->events;
+	while (eva && evb) {
+		if (!same_event(eva, evb))
+			return 0;
+		eva = eva->next;
+		evb = evb->next;
+	}
+	return eva == evb;
+}
+
+static int might_be_same_device(struct divecomputer *a, struct divecomputer *b)
+{
+	/* No dive computer model? That matches anything */
+	if (!a->model || !b->model)
+		return 1;
+
+	/* Otherwise at least the model names have to match */
+	if (strcasecmp(a->model, b->model))
+		return 0;
+
+	/* No device ID? Match */
+	if (!a->deviceid || !b->deviceid)
+		return 1;
+
+	return a->deviceid == b->deviceid;
+}
+
+static void remove_redundant_dc(struct divecomputer *dc, int prefer_downloaded)
+{
+	do {
+		struct divecomputer **p = &dc->next;
+
+		/* Check this dc against all the following ones.. */
+		while (*p) {
+			struct divecomputer *check = *p;
+			if (same_dc(dc, check) || (prefer_downloaded && might_be_same_device(dc, check))) {
+				*p = check->next;
+				check->next = NULL;
+				free_dc(check);
+				continue;
+			}
+			p = &check->next;
+		}
+
+		/* .. and then continue down the chain, but we */
+		prefer_downloaded = 0;
+		dc = dc->next;
+	} while (dc);
+}
+
+static void clear_dc(struct divecomputer *dc)
+{
+	memset(dc, 0, sizeof(*dc));
+}
+
+static struct divecomputer *find_matching_computer(struct divecomputer *match, struct divecomputer *list)
+{
+	struct divecomputer *p;
+
+	while ((p = list) != NULL) {
+		list = list->next;
+
+		if (might_be_same_device(match, p))
+			break;
+	}
+	return p;
+}
+
+
+static void copy_dive_computer(struct divecomputer *res, struct divecomputer *a)
+{
+	*res = *a;
+	res->model = copy_string(a->model);
+	res->samples = res->alloc_samples = 0;
+	res->sample = NULL;
+	res->events = NULL;
+	res->next = NULL;
+}
+
+/*
+ * Join dive computers with a specific time offset between
+ * them.
+ *
+ * Use the dive computer ID's (or names, if ID's are missing)
+ * to match them up. If we find a matching dive computer, we
+ * merge them. If not, we just take the data from 'a'.
+ */
+static void interleave_dive_computers(struct divecomputer *res,
+				      struct divecomputer *a, struct divecomputer *b, int offset)
+{
+	do {
+		struct divecomputer *match;
+
+		copy_dive_computer(res, a);
+
+		match = find_matching_computer(a, b);
+		if (match) {
+			merge_events(res, a, match, offset);
+			merge_samples(res, a, match, offset);
+			/* Use the diveid of the later dive! */
+			if (offset > 0)
+				res->diveid = match->diveid;
+		} else {
+			res->sample = a->sample;
+			res->samples = a->samples;
+			res->events = a->events;
+			a->sample = NULL;
+			a->samples = 0;
+			a->events = NULL;
+		}
+		a = a->next;
+		if (!a)
+			break;
+		res->next = calloc(1, sizeof(struct divecomputer));
+		res = res->next;
+	} while (res);
+}
+
+
+/*
+ * Join dive computer information.
+ *
+ * If we have old-style dive computer information (no model
+ * name etc), we will prefer a new-style one and just throw
+ * away the old. We're assuming it's a re-download.
+ *
+ * Otherwise, we'll just try to keep all the information,
+ * unless the user has specified that they prefer the
+ * downloaded computer, in which case we'll aggressively
+ * try to throw out old information that *might* be from
+ * that one.
+ */
+static void join_dive_computers(struct divecomputer *res, struct divecomputer *a, struct divecomputer *b, int prefer_downloaded)
+{
+	struct divecomputer *tmp;
+
+	if (a->model && !b->model) {
+		*res = *a;
+		clear_dc(a);
+		return;
+	}
+	if (b->model && !a->model) {
+		*res = *b;
+		clear_dc(b);
+		return;
+	}
+
+	*res = *a;
+	clear_dc(a);
+	tmp = res;
+	while (tmp->next)
+		tmp = tmp->next;
+
+	tmp->next = calloc(1, sizeof(*tmp));
+	*tmp->next = *b;
+	clear_dc(b);
+
+	remove_redundant_dc(res, prefer_downloaded);
+}
+
+static bool tag_seen_before(struct tag_entry *start, struct tag_entry *before)
+{
+	while (start && start != before) {
+		if (same_string(start->tag->name, before->tag->name))
+			return true;
+		start = start->next;
+	}
+	return false;
+}
+
+/* remove duplicates and empty nodes */
+void taglist_cleanup(struct tag_entry **tag_list)
+{
+	struct tag_entry **tl = tag_list;
+	while (*tl) {
+		/* skip tags that are empty or that we have seen before */
+		if (same_string((*tl)->tag->name, "") || tag_seen_before(*tag_list, *tl)) {
+			*tl = (*tl)->next;
+			continue;
+		}
+		tl = &(*tl)->next;
+	}
+}
+
+int taglist_get_tagstring(struct tag_entry *tag_list, char *buffer, int len)
+{
+	int i = 0;
+	struct tag_entry *tmp;
+	tmp = tag_list;
+	memset(buffer, 0, len);
+	while (tmp != NULL) {
+		int newlength = strlen(tmp->tag->name);
+		if (i > 0)
+			newlength += 2;
+		if ((i + newlength) < len) {
+			if (i > 0) {
+				strcpy(buffer + i, ", ");
+				strcpy(buffer + i + 2, tmp->tag->name);
+			} else {
+				strcpy(buffer, tmp->tag->name);
+			}
+		} else {
+			return i;
+		}
+		i += newlength;
+		tmp = tmp->next;
+	}
+	return i;
+}
+
+static inline void taglist_free_divetag(struct divetag *tag)
+{
+	if (tag->name != NULL)
+		free(tag->name);
+	if (tag->source != NULL)
+		free(tag->source);
+	free(tag);
+}
+
+/* Add a tag to the tag_list, keep the list sorted */
+static struct divetag *taglist_add_divetag(struct tag_entry **tag_list, struct divetag *tag)
+{
+	struct tag_entry *next, *entry;
+
+	while ((next = *tag_list) != NULL) {
+		int cmp = strcmp(next->tag->name, tag->name);
+
+		/* Already have it? */
+		if (!cmp)
+			return next->tag;
+		/* Is the entry larger? If so, insert here */
+		if (cmp > 0)
+			break;
+		/* Continue traversing the list */
+		tag_list = &next->next;
+	}
+
+	/* Insert in front of it */
+	entry = malloc(sizeof(struct tag_entry));
+	entry->next = next;
+	entry->tag = tag;
+	*tag_list = entry;
+	return tag;
+}
+
+struct divetag *taglist_add_tag(struct tag_entry **tag_list, const char *tag)
+{
+	size_t i = 0;
+	int is_default_tag = 0;
+	struct divetag *ret_tag, *new_tag;
+	const char *translation;
+	new_tag = malloc(sizeof(struct divetag));
+
+	for (i = 0; i < sizeof(default_tags) / sizeof(char *); i++) {
+		if (strcmp(default_tags[i], tag) == 0) {
+			is_default_tag = 1;
+			break;
+		}
+	}
+	/* Only translate default tags */
+	if (is_default_tag) {
+		translation = translate("gettextFromC", tag);
+		new_tag->name = malloc(strlen(translation) + 1);
+		memcpy(new_tag->name, translation, strlen(translation) + 1);
+		new_tag->source = malloc(strlen(tag) + 1);
+		memcpy(new_tag->source, tag, strlen(tag) + 1);
+	} else {
+		new_tag->source = NULL;
+		new_tag->name = malloc(strlen(tag) + 1);
+		memcpy(new_tag->name, tag, strlen(tag) + 1);
+	}
+	/* Try to insert new_tag into g_tag_list if we are not operating on it */
+	if (tag_list != &g_tag_list) {
+		ret_tag = taglist_add_divetag(&g_tag_list, new_tag);
+		/* g_tag_list already contains new_tag, free the duplicate */
+		if (ret_tag != new_tag)
+			taglist_free_divetag(new_tag);
+		ret_tag = taglist_add_divetag(tag_list, ret_tag);
+	} else {
+		ret_tag = taglist_add_divetag(tag_list, new_tag);
+		if (ret_tag != new_tag)
+			taglist_free_divetag(new_tag);
+	}
+	return ret_tag;
+}
+
+void taglist_free(struct tag_entry *entry)
+{
+	STRUCTURED_LIST_FREE(struct tag_entry, entry, free)
+}
+
+/* Merge src1 and src2, write to *dst */
+static void taglist_merge(struct tag_entry **dst, struct tag_entry *src1, struct tag_entry *src2)
+{
+	struct tag_entry *entry;
+
+	for (entry = src1; entry; entry = entry->next)
+		taglist_add_divetag(dst, entry->tag);
+	for (entry = src2; entry; entry = entry->next)
+		taglist_add_divetag(dst, entry->tag);
+}
+
+void taglist_init_global()
+{
+	size_t i;
+
+	for (i = 0; i < sizeof(default_tags) / sizeof(char *); i++)
+		taglist_add_tag(&g_tag_list, default_tags[i]);
+}
+
+bool taglist_contains(struct tag_entry *tag_list, const char *tag)
+{
+	while (tag_list) {
+		if (same_string(tag_list->tag->name, tag))
+			return true;
+		tag_list = tag_list->next;
+	}
+	return false;
+}
+
+// check if all tags in subtl are included in supertl (so subtl is a subset of supertl)
+static bool taglist_contains_all(struct tag_entry *subtl, struct tag_entry *supertl)
+{
+	while (subtl) {
+		if (!taglist_contains(supertl, subtl->tag->name))
+			return false;
+		subtl = subtl->next;
+	}
+	return true;
+}
+
+struct tag_entry *taglist_added(struct tag_entry *original_list, struct tag_entry *new_list)
+{
+	struct tag_entry *added_list = NULL;
+	while (new_list) {
+		if (!taglist_contains(original_list, new_list->tag->name))
+			taglist_add_tag(&added_list, new_list->tag->name);
+		new_list = new_list->next;
+	}
+	return added_list;
+}
+
+void dump_taglist(const char *intro, struct tag_entry *tl)
+{
+	char *comma = "";
+	fprintf(stderr, "%s", intro);
+	while(tl) {
+		fprintf(stderr, "%s %s", comma, tl->tag->name);
+		comma = ",";
+		tl = tl->next;
+	}
+	fprintf(stderr, "\n");
+}
+
+// if tl1 is both a subset and superset of tl2 they must be the same
+bool taglist_equal(struct tag_entry *tl1, struct tag_entry *tl2)
+{
+	return taglist_contains_all(tl1, tl2) && taglist_contains_all(tl2, tl1);
+}
+
+// count the dives where the tag list contains the given tag
+int count_dives_with_tag(const char *tag)
+{
+	int i, counter = 0;
+	struct dive *d;
+
+	for_each_dive (i, d) {
+		if (same_string(tag, "")) {
+			// count dives with no tags
+			if (d->tag_list == NULL)
+				counter++;
+		} else if (taglist_contains(d->tag_list, tag)) {
+			counter++;
+		}
+	}
+	return counter;
+}
+
+extern bool string_sequence_contains(const char *string_sequence, const char *text);
+
+// count the dives where the person is included in the comma separated string sequences of buddies or divemasters
+int count_dives_with_person(const char *person)
+{
+	int i, counter = 0;
+	struct dive *d;
+
+	for_each_dive (i, d) {
+		if (same_string(person, "")) {
+			// solo dive
+			if (same_string(d->buddy, "") && same_string(d->divemaster, ""))
+				counter++;
+		} else if (string_sequence_contains(d->buddy, person) || string_sequence_contains(d->divemaster, person)) {
+			counter++;
+		}
+	}
+	return counter;
+}
+
+// count the dives with exactly the location
+int count_dives_with_location(const char *location)
+{
+	int i, counter = 0;
+	struct dive *d;
+
+	for_each_dive (i, d) {
+		if (same_string(get_dive_location(d), location))
+			counter++;
+	}
+	return counter;
+}
+
+// count the dives with exactly the suit
+int count_dives_with_suit(const char *suit)
+{
+	int i, counter = 0;
+	struct dive *d;
+
+	for_each_dive (i, d) {
+		if (same_string(d->suit, suit))
+			counter++;
+	}
+	return counter;
+}
+
+/*
+ * Merging two dives can be subtle, because there's two different ways
+ * of merging:
+ *
+ * (a) two distinctly _different_ dives that have the same dive computer
+ *     are merged into one longer dive, because the user asked for it
+ *     in the divelist.
+ *
+ *     Because this case is with the same dive computer, we *know* the
+ *     two must have a different start time, and "offset" is the relative
+ *     time difference between the two.
+ *
+ * (a) two different dive computers that we might want to merge into
+ *     one single dive with multiple dive computers.
+ *
+ *     This is the "try_to_merge()" case, which will have offset == 0,
+ *     even if the dive times might be different.
+ */
+struct dive *merge_dives(struct dive *a, struct dive *b, int offset, bool prefer_downloaded)
+{
+	struct dive *res = alloc_dive();
+	struct dive *dl = NULL;
+
+	if (offset) {
+		/*
+		 * If "likely_same_dive()" returns true, that means that
+		 * it is *not* the same dive computer, and we do not want
+		 * to try to turn it into a single longer dive. So we'd
+		 * join them as two separate dive computers at zero offset.
+		 */
+		if (likely_same_dive(a, b))
+			offset = 0;
+	} else {
+		/* Aim for newly downloaded dives to be 'b' (keep old dive data first) */
+		if (a->downloaded && !b->downloaded) {
+			struct dive *tmp = a;
+			a = b;
+			b = tmp;
+		}
+		if (prefer_downloaded && b->downloaded)
+			dl = b;
+	}
+
+	res->when = dl ? dl->when : a->when;
+	res->selected = a->selected || b->selected;
+	merge_trip(res, a, b);
+	MERGE_TXT(res, a, b, notes);
+	MERGE_TXT(res, a, b, buddy);
+	MERGE_TXT(res, a, b, divemaster);
+	MERGE_MAX(res, a, b, rating);
+	MERGE_TXT(res, a, b, suit);
+	MERGE_MAX(res, a, b, number);
+	MERGE_NONZERO(res, a, b, cns);
+	MERGE_NONZERO(res, a, b, visibility);
+	MERGE_NONZERO(res, a, b, picture_list);
+	taglist_merge(&res->tag_list, a->tag_list, b->tag_list);
+	merge_equipment(res, a, b);
+	merge_airtemps(res, a, b);
+	if (dl) {
+		/* If we prefer downloaded, do those first, and get rid of "might be same" computers */
+		join_dive_computers(&res->dc, &dl->dc, &a->dc, 1);
+	} else if (offset && might_be_same_device(&a->dc, &b->dc))
+		interleave_dive_computers(&res->dc, &a->dc, &b->dc, offset);
+	else
+		join_dive_computers(&res->dc, &a->dc, &b->dc, 0);
+	res->dive_site_uuid = a->dive_site_uuid ?: b->dive_site_uuid;
+	fixup_dive(res);
+	return res;
+}
+
+// copy_dive(), but retaining the new ID for the copied dive
+static struct dive *create_new_copy(struct dive *from)
+{
+	struct dive *to = alloc_dive();
+	int id;
+
+	// alloc_dive() gave us a new ID, we just need to
+	// make sure it's not overwritten.
+	id = to->id;
+	copy_dive(from, to);
+	to->id = id;
+	return to;
+}
+
+static void force_fixup_dive(struct dive *d)
+{
+	struct divecomputer *dc = &d->dc;
+	int old_temp = dc->watertemp.mkelvin;
+	int old_mintemp = d->mintemp.mkelvin;
+	int old_maxtemp = d->maxtemp.mkelvin;
+	duration_t old_duration = d->duration;
+
+	d->maxdepth.mm = 0;
+	dc->maxdepth.mm = 0;
+	d->watertemp.mkelvin = 0;
+	dc->watertemp.mkelvin = 0;
+	d->duration.seconds = 0;
+	d->maxtemp.mkelvin = 0;
+	d->mintemp.mkelvin = 0;
+
+	fixup_dive(d);
+
+	if (!d->watertemp.mkelvin)
+		d->watertemp.mkelvin = old_temp;
+
+	if (!dc->watertemp.mkelvin)
+		dc->watertemp.mkelvin = old_temp;
+
+	if (!d->maxtemp.mkelvin)
+		d->maxtemp.mkelvin = old_maxtemp;
+
+	if (!d->mintemp.mkelvin)
+		d->mintemp.mkelvin = old_mintemp;
+
+	if (!d->duration.seconds)
+		d->duration = old_duration;
+
+}
+
+/*
+ * Split a dive that has a surface interval from samples 'a' to 'b'
+ * into two dives.
+ */
+static int split_dive_at(struct dive *dive, int a, int b)
+{
+	int i, nr;
+	uint32_t t;
+	struct dive *d1, *d2;
+	struct divecomputer *dc1, *dc2;
+	struct event *event, **evp;
+
+	/* if we can't find the dive in the dive list, don't bother */
+	if ((nr = get_divenr(dive)) < 0)
+		return 0;
+
+	/* We're not trying to be efficient here.. */
+	d1 = create_new_copy(dive);
+	d2 = create_new_copy(dive);
+
+	/* now unselect the first first segment so we don't keep all
+	 * dives selected by mistake. But do keep the second one selected
+	 * so the algorithm keeps splitting the dive further */
+	d1->selected = false;
+
+	dc1 = &d1->dc;
+	dc2 = &d2->dc;
+	/*
+	 * Cut off the samples of d1 at the beginning
+	 * of the interval.
+	 */
+	dc1->samples = a;
+
+	/* And get rid of the 'b' first samples of d2 */
+	dc2->samples -= b;
+	memmove(dc2->sample, dc2->sample+b, dc2->samples * sizeof(struct sample));
+
+	/*
+	 * This is where we cut off events from d1,
+	 * and shift everything in d2
+	 */
+	t = dc2->sample[0].time.seconds;
+	d2->when += t;
+	for (i = 0; i < dc2->samples; i++)
+		dc2->sample[i].time.seconds -= t;
+
+	/* Remove the events past 't' from d1 */
+	evp = &dc1->events;
+	while ((event = *evp) != NULL && event->time.seconds < t)
+		evp = &event->next;
+	*evp = NULL;
+	while (event) {
+		struct event *next = event->next;
+		free(event);
+		event = next;
+	}
+
+	/* Remove the events before 't' from d2, and shift the rest */
+	evp = &dc2->events;
+	while ((event = *evp) != NULL) {
+		if (event->time.seconds < t) {
+			*evp = event->next;
+			free(event);
+		} else {
+			event->time.seconds -= t;
+		}
+	}
+
+	force_fixup_dive(d1);
+	force_fixup_dive(d2);
+
+	if (dive->divetrip) {
+		d1->divetrip = d2->divetrip = 0;
+		add_dive_to_trip(d1, dive->divetrip);
+		add_dive_to_trip(d2, dive->divetrip);
+	}
+
+	delete_single_dive(nr);
+	add_single_dive(nr, d1);
+
+	/*
+	 * Was the dive numbered? If it was the last dive, then we'll
+	 * increment the dive number for the tail part that we split off.
+	 * Otherwise the tail is unnumbered.
+	 */
+	if (d2->number) {
+		if (dive_table.nr == nr + 1)
+			d2->number++;
+		else
+			d2->number = 0;
+	}
+	add_single_dive(nr + 1, d2);
+
+	mark_divelist_changed(true);
+
+	return 1;
+}
+
+/* in freedive mode we split for as little as 10 seconds on the surface,
+ * otherwise we use a minute */
+static bool should_split(struct divecomputer *dc, int t1, int t2)
+{
+	int threshold = dc->divemode == FREEDIVE ? 10 : 60;
+
+	return t2 - t1 >= threshold;
+}
+
+/*
+ * Try to split a dive into multiple dives at a surface interval point.
+ *
+ * NOTE! We will not split dives with multiple dive computers, and
+ * only split when there is at least one surface event that has
+ * non-surface events on both sides.
+ *
+ * In other words, this is a (simplified) reversal of the dive merging.
+ */
+int split_dive(struct dive *dive)
+{
+	int i;
+	int at_surface, surface_start;
+	struct divecomputer *dc;
+
+	if (!dive || (dc = &dive->dc)->next)
+		return 0;
+
+	surface_start = 0;
+	at_surface = 1;
+	for (i = 1; i < dc->samples; i++) {
+		struct sample *sample = dc->sample+i;
+		int surface_sample = sample->depth.mm < SURFACE_THRESHOLD;
+
+		/*
+		 * We care about the transition from and to depth 0,
+		 * not about the depth staying similar.
+		 */
+		if (at_surface == surface_sample)
+			continue;
+		at_surface = surface_sample;
+
+		// Did it become surface after having been non-surface? We found the start
+		if (at_surface) {
+			surface_start = i;
+			continue;
+		}
+
+		// Going down again? We want at least a minute from
+		// the surface start.
+		if (!surface_start)
+			continue;
+		if (!should_split(dc, dc->sample[surface_start].time.seconds, sample[i - 1].time.seconds))
+			continue;
+
+		return split_dive_at(dive, surface_start, i-1);
+	}
+	return 0;
+}
+
+/*
+ * "dc_maxtime()" is how much total time this dive computer
+ * has for this dive. Note that it can differ from "duration"
+ * if there are surface events in the middle.
+ *
+ * Still, we do ignore all but the last surface samples from the
+ * end, because some divecomputers just generate lots of them.
+ */
+static inline int dc_totaltime(const struct divecomputer *dc)
+{
+	int time = dc->duration.seconds;
+	int nr = dc->samples;
+
+	while (nr--) {
+		struct sample *s = dc->sample + nr;
+		time = s->time.seconds;
+		if (s->depth.mm >= SURFACE_THRESHOLD)
+			break;
+	}
+	return time;
+}
+
+/*
+ * The end of a dive is actually not trivial, because "duration"
+ * is not the duration until the end, but the time we spend under
+ * water, which can be very different if there are surface events
+ * during the dive.
+ *
+ * So walk the dive computers, looking for the longest actual
+ * time in the samples (and just default to the dive duration if
+ * there are no samples).
+ */
+static inline int dive_totaltime(const struct dive *dive)
+{
+	int time =  dive->duration.seconds;
+	const struct divecomputer *dc;
+
+	for_each_dc(dive, dc) {
+		int dc_time = dc_totaltime(dc);
+		if (dc_time > time)
+			time = dc_time;
+	}
+	return time;
+}
+
+timestamp_t dive_endtime(const struct dive *dive)
+{
+	return dive->when + dive_totaltime(dive);
+}
+
+struct dive *find_dive_including(timestamp_t when)
+{
+	int i;
+	struct dive *dive;
+
+	/* binary search, anyone? Too lazy for now;
+	 * also we always use the duration from the first divecomputer
+	 *     could this ever be a problem? */
+	for_each_dive (i, dive) {
+		if (dive->when <= when && when <= dive_endtime(dive))
+			return dive;
+	}
+	return NULL;
+}
+
+bool time_during_dive_with_offset(struct dive *dive, timestamp_t when, timestamp_t offset)
+{
+	timestamp_t start = dive->when;
+	timestamp_t end = dive_endtime(dive);
+	return start - offset <= when && when <= end + offset;
+}
+
+bool dive_within_time_range(struct dive *dive, timestamp_t when, timestamp_t offset)
+{
+	timestamp_t start = dive->when;
+	timestamp_t end = dive_endtime(dive);
+	return when - offset <= start && end <= when + offset;
+}
+
+/* find the n-th dive that is part of a group of dives within the offset around 'when'.
+ *  How is that for a vague definition of what this function should do... */
+struct dive *find_dive_n_near(timestamp_t when, int n, timestamp_t offset)
+{
+	int i, j = 0;
+	struct dive *dive;
+
+	for_each_dive (i, dive) {
+		if (dive_within_time_range(dive, when, offset))
+			if (++j == n)
+				return dive;
+	}
+	return NULL;
+}
+
+void shift_times(const timestamp_t amount)
+{
+	int i;
+	struct dive *dive;
+
+	for_each_dive (i, dive) {
+		if (!dive->selected)
+			continue;
+		dive->when += amount;
+		invalidate_dive_cache(dive);
+	}
+}
+
+timestamp_t get_times()
+{
+	int i;
+	struct dive *dive;
+
+	for_each_dive (i, dive) {
+		if (dive->selected)
+			break;
+	}
+	return dive->when;
+}
+
+void set_save_userid_local(short value)
+{
+	prefs.save_userid_local = value;
+}
+
+void set_userid(char *rUserId)
+{
+	if (prefs.userid)
+		free(prefs.userid);
+	prefs.userid = strdup(rUserId);
+	if (strlen(prefs.userid) > 30)
+		prefs.userid[30]='\0';
+}
+
+/* this sets a usually unused copy of the preferences with the units
+ * that were active the last time the dive list was saved to git storage
+ * (this isn't used in XML files); storing the unit preferences in the
+ * data file is usually pointless (that's a setting of the software,
+ * not a property of the data), but it's a great hint of what the user
+ * might expect to see when creating a backend service that visualizes
+ * the dive list without Subsurface running - so this is basically a
+ * functionality for the core library that Subsurface itself doesn't
+ * use but that another consumer of the library (like an HTML exporter)
+ * will need */
+void set_informational_units(char *units)
+{
+	if (strstr(units, "METRIC")) {
+		informational_prefs.unit_system = METRIC;
+	} else if (strstr(units, "IMPERIAL")) {
+		informational_prefs.unit_system = IMPERIAL;
+	} else if (strstr(units, "PERSONALIZE")) {
+		informational_prefs.unit_system = PERSONALIZE;
+		if (strstr(units, "METERS"))
+			informational_prefs.units.length = METERS;
+		if (strstr(units, "FEET"))
+			informational_prefs.units.length = FEET;
+		if (strstr(units, "LITER"))
+			informational_prefs.units.volume = LITER;
+		if (strstr(units, "CUFT"))
+			informational_prefs.units.volume = CUFT;
+		if (strstr(units, "BAR"))
+			informational_prefs.units.pressure = BAR;
+		if (strstr(units, "PSI"))
+			informational_prefs.units.pressure = PSI;
+		if (strstr(units, "PASCAL"))
+			informational_prefs.units.pressure = PASCAL;
+		if (strstr(units, "CELSIUS"))
+			informational_prefs.units.temperature = CELSIUS;
+		if (strstr(units, "FAHRENHEIT"))
+			informational_prefs.units.temperature = FAHRENHEIT;
+		if (strstr(units, "KG"))
+			informational_prefs.units.weight = KG;
+		if (strstr(units, "LBS"))
+			informational_prefs.units.weight = LBS;
+		if (strstr(units, "SECONDS"))
+			informational_prefs.units.vertical_speed_time = SECONDS;
+		if (strstr(units, "MINUTES"))
+			informational_prefs.units.vertical_speed_time = MINUTES;
+	}
+}
+
+void average_max_depth(struct diveplan *dive, int *avg_depth, int *max_depth)
+{
+	int integral = 0;
+	int last_time = 0;
+	int last_depth = 0;
+	struct divedatapoint *dp = dive->dp;
+
+	*max_depth = 0;
+
+	while (dp) {
+		if (dp->time) {
+			/* Ignore gas indication samples */
+			integral += (dp->depth + last_depth) * (dp->time - last_time) / 2;
+			last_time = dp->time;
+			last_depth = dp->depth;
+			if (dp->depth > *max_depth)
+				*max_depth = dp->depth;
+		}
+		dp = dp->next;
+	}
+	if (last_time)
+		*avg_depth = integral / last_time;
+	else
+		*avg_depth = *max_depth = 0;
+}
+
+struct picture *alloc_picture()
+{
+	struct picture *pic = malloc(sizeof(struct picture));
+	if (!pic)
+		exit(1);
+	memset(pic, 0, sizeof(struct picture));
+	return pic;
+}
+
+static bool new_picture_for_dive(struct dive *d, char *filename)
+{
+	FOR_EACH_PICTURE (d) {
+		if (same_string(picture->filename, filename))
+			return false;
+	}
+	return true;
+}
+
+// only add pictures that have timestamps between 30 minutes before the dive and
+// 30 minutes after the dive ends
+#define D30MIN (30 * 60)
+bool dive_check_picture_time(struct dive *d, int shift_time, timestamp_t timestamp)
+{
+	offset_t offset;
+	if (timestamp) {
+		offset.seconds = timestamp - d->when + shift_time;
+		if (offset.seconds > -D30MIN && offset.seconds < dive_totaltime(d) + D30MIN) {
+			// this picture belongs to this dive
+			return true;
+		}
+	}
+	return false;
+}
+
+bool picture_check_valid(char *filename, int shift_time)
+{
+	int i;
+	struct dive *dive;
+
+	timestamp_t timestamp = picture_get_timestamp(filename);
+	for_each_dive (i, dive)
+		if (dive->selected && dive_check_picture_time(dive, shift_time, timestamp))
+			return true;
+	return false;
+}
+
+void dive_create_picture(struct dive *dive, char *filename, int shift_time, bool match_all)
+{
+	timestamp_t timestamp = picture_get_timestamp(filename);
+	if (!new_picture_for_dive(dive, filename))
+		return;
+	if (!match_all && !dive_check_picture_time(dive, shift_time, timestamp))
+		return;
+
+	struct picture *picture = alloc_picture();
+	picture->filename = strdup(filename);
+	picture->offset.seconds = timestamp - dive->when + shift_time;
+	picture_load_exif_data(picture);
+
+	dive_add_picture(dive, picture);
+	dive_set_geodata_from_picture(dive, picture);
+	invalidate_dive_cache(dive);
+}
+
+void dive_add_picture(struct dive *dive, struct picture *newpic)
+{
+	struct picture **pic_ptr = &dive->picture_list;
+	/* let's keep the list sorted by time */
+	while (*pic_ptr && (*pic_ptr)->offset.seconds <= newpic->offset.seconds)
+		pic_ptr = &(*pic_ptr)->next;
+	newpic->next = *pic_ptr;
+	*pic_ptr = newpic;
+	cache_picture(newpic);
+	return;
+}
+
+unsigned int dive_get_picture_count(struct dive *dive)
+{
+	unsigned int i = 0;
+	FOR_EACH_PICTURE (dive)
+		i++;
+	return i;
+}
+
+void dive_set_geodata_from_picture(struct dive *dive, struct picture *picture)
+{
+	struct dive_site *ds = get_dive_site_by_uuid(dive->dive_site_uuid);
+	if (!dive_site_has_gps_location(ds) && (picture->latitude.udeg || picture->longitude.udeg)) {
+		if (ds) {
+			ds->latitude = picture->latitude;
+			ds->longitude = picture->longitude;
+		} else {
+			dive->dive_site_uuid = create_dive_site_with_gps("", picture->latitude, picture->longitude, dive->when);
+			invalidate_dive_cache(dive);
+		}
+	}
+}
+
+void picture_free(struct picture *picture)
+{
+	if (!picture)
+		return;
+	free(picture->filename);
+	free(picture->hash);
+	free(picture);
+}
+
+// When handling pictures in different threads, we need to copy them so we don't
+// run into problems when the main thread frees the picture.
+
+struct picture *clone_picture(struct picture *src)
+{
+	struct picture *dst;
+
+	dst = alloc_picture();
+	copy_pl(src, dst);
+	return dst;
+}
+
+void dive_remove_picture(char *filename)
+{
+	struct picture **picture = &current_dive->picture_list;
+	while (picture && !same_string((*picture)->filename, filename))
+		picture = &(*picture)->next;
+	if (picture) {
+		struct picture *temp = (*picture)->next;
+		picture_free(*picture);
+		*picture = temp;
+		invalidate_dive_cache(current_dive);
+	}
+}
+
+/* this always acts on the current divecomputer of the current dive */
+void make_first_dc()
+{
+	struct divecomputer *dc = &current_dive->dc;
+	struct divecomputer *newdc = malloc(sizeof(*newdc));
+	struct divecomputer *cur_dc = current_dc; /* needs to be in a local variable so the macro isn't re-executed */
+
+	/* skip the current DC in the linked list */
+	while (dc && dc->next != cur_dc)
+		dc = dc->next;
+	if (!dc) {
+		free(newdc);
+		fprintf(stderr, "data inconsistent: can't find the current DC");
+		return;
+	}
+	dc->next = cur_dc->next;
+	*newdc = current_dive->dc;
+	current_dive->dc = *cur_dc;
+	current_dive->dc.next = newdc;
+	free(cur_dc);
+	invalidate_dive_cache(current_dive);
+}
+
+/* always acts on the current dive */
+unsigned int count_divecomputers(void)
+{
+	int ret = 1;
+	struct divecomputer *dc = current_dive->dc.next;
+	while (dc) {
+		ret++;
+		dc = dc->next;
+	}
+	return ret;
+}
+
+/* always acts on the current dive */
+void delete_current_divecomputer(void)
+{
+	struct divecomputer *dc = current_dc;
+
+	if (dc == &current_dive->dc) {
+		/* remove the first one, so copy the second one in place of the first and free the second one
+		 * be careful about freeing the no longer needed structures - since we copy things around we can't use free_dc()*/
+		struct divecomputer *fdc = dc->next;
+		free(dc->sample);
+		free((void *)dc->model);
+		free_events(dc->events);
+		memcpy(dc, fdc, sizeof(struct divecomputer));
+		free(fdc);
+	} else {
+		struct divecomputer *pdc = &current_dive->dc;
+		while (pdc->next != dc && pdc->next)
+			pdc = pdc->next;
+		if (pdc->next == dc) {
+			pdc->next = dc->next;
+			free_dc(dc);
+		}
+	}
+	if (dc_number == count_divecomputers())
+		dc_number--;
+	invalidate_dive_cache(current_dive);
+}
+
+/* helper function to make it easier to work with our structures
+ * we don't interpolate here, just use the value from the last sample up to that time */
+int get_depth_at_time(struct divecomputer *dc, unsigned int time)
+{
+	int depth = 0;
+	if (dc && dc->sample)
+		for (int i = 0; i < dc->samples; i++) {
+			if (dc->sample[i].time.seconds > time)
+				break;
+			depth = dc->sample[i].depth.mm;
+		}
+	return depth;
+}