Statistics: remove global state / calculate only when needed

Statistics were calculated into global variables every time the
current dive was changed.

Calculate statistics only when needed and into a structure
provided by the caller.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

7 files changed, 142 insertions, 108 deletions

diff --git a/core/divelogexportlogic.cpp b/core/divelogexportlogic.cpp
index cb700e79a..27a42fbf7 100644
--- a/core/divelogexportlogic.cpp
+++ b/core/divelogexportlogic.cpp
@@ -75,42 +75,44 @@ static void exportHTMLstatistics(const QString filename, struct htmlExportSettin
 	QFile file(filename);
 	file.open(QIODevice::WriteOnly | QIODevice::Text);
 	QTextStream out(&file);
+	stats_summary_auto_free stats;
 
 	stats_t total_stats;
 
+	calculate_stats_summary(&stats);
 	total_stats.selection_size = 0;
 	total_stats.total_time.seconds = 0;
 
 	int i = 0;
 	out << "divestat=[";
 	if (hes.yearlyStatistics) {
-		while (stats_yearly != NULL && stats_yearly[i].period) {
+		while (stats.stats_yearly != NULL && stats.stats_yearly[i].period) {
 			out << "{";
-			out << "\"YEAR\":\"" << stats_yearly[i].period << "\",";
-			out << "\"DIVES\":\"" << stats_yearly[i].selection_size << "\",";
-			out << "\"TOTAL_TIME\":\"" << get_dive_duration_string(stats_yearly[i].total_time.seconds,
+			out << "\"YEAR\":\"" << stats.stats_yearly[i].period << "\",";
+			out << "\"DIVES\":\"" << stats.stats_yearly[i].selection_size << "\",";
+			out << "\"TOTAL_TIME\":\"" << get_dive_duration_string(stats.stats_yearly[i].total_time.seconds,
 											gettextFromC::tr("h"), gettextFromC::tr("min"), gettextFromC::tr("sec"), " ") << "\",";
-			out << "\"AVERAGE_TIME\":\"" << get_minutes(stats_yearly[i].total_time.seconds / stats_yearly[i].selection_size) << "\",";
-			out << "\"SHORTEST_TIME\":\"" << get_minutes(stats_yearly[i].shortest_time.seconds) << "\",";
-			out << "\"LONGEST_TIME\":\"" << get_minutes(stats_yearly[i].longest_time.seconds) << "\",";
-			out << "\"AVG_DEPTH\":\"" << get_depth_string(stats_yearly[i].avg_depth) << "\",";
-			out << "\"MIN_DEPTH\":\"" << get_depth_string(stats_yearly[i].min_depth) << "\",";
-			out << "\"MAX_DEPTH\":\"" << get_depth_string(stats_yearly[i].max_depth) << "\",";
-			out << "\"AVG_SAC\":\"" << get_volume_string(stats_yearly[i].avg_sac) << "\",";
-			out << "\"MIN_SAC\":\"" << get_volume_string(stats_yearly[i].min_sac) << "\",";
-			out << "\"MAX_SAC\":\"" << get_volume_string(stats_yearly[i].max_sac) << "\",";
-			if (stats_yearly[i].combined_count) {
+			out << "\"AVERAGE_TIME\":\"" << get_minutes(stats.stats_yearly[i].total_time.seconds / stats.stats_yearly[i].selection_size) << "\",";
+			out << "\"SHORTEST_TIME\":\"" << get_minutes(stats.stats_yearly[i].shortest_time.seconds) << "\",";
+			out << "\"LONGEST_TIME\":\"" << get_minutes(stats.stats_yearly[i].longest_time.seconds) << "\",";
+			out << "\"AVG_DEPTH\":\"" << get_depth_string(stats.stats_yearly[i].avg_depth) << "\",";
+			out << "\"MIN_DEPTH\":\"" << get_depth_string(stats.stats_yearly[i].min_depth) << "\",";
+			out << "\"MAX_DEPTH\":\"" << get_depth_string(stats.stats_yearly[i].max_depth) << "\",";
+			out << "\"AVG_SAC\":\"" << get_volume_string(stats.stats_yearly[i].avg_sac) << "\",";
+			out << "\"MIN_SAC\":\"" << get_volume_string(stats.stats_yearly[i].min_sac) << "\",";
+			out << "\"MAX_SAC\":\"" << get_volume_string(stats.stats_yearly[i].max_sac) << "\",";
+			if (stats.stats_yearly[i].combined_count) {
 				temperature_t avg_temp;
-				avg_temp.mkelvin = stats_yearly[i].combined_temp.mkelvin / stats_yearly[i].combined_count;
+				avg_temp.mkelvin = stats.stats_yearly[i].combined_temp.mkelvin / stats.stats_yearly[i].combined_count;
 				out << "\"AVG_TEMP\":\"" << get_temperature_string(avg_temp) << "\",";
 			} else {
 				out << "\"AVG_TEMP\":\"0.0\",";
 			}
-			out << "\"MIN_TEMP\":\"" << (stats_yearly[i].min_temp.mkelvin == 0 ? 0 : get_temperature_string(stats_yearly[i].min_temp)) << "\",";
-			out << "\"MAX_TEMP\":\"" << (stats_yearly[i].max_temp.mkelvin == 0 ? 0 : get_temperature_string(stats_yearly[i].max_temp)) << "\",";
+			out << "\"MIN_TEMP\":\"" << (stats.stats_yearly[i].min_temp.mkelvin == 0 ? 0 : get_temperature_string(stats.stats_yearly[i].min_temp)) << "\",";
+			out << "\"MAX_TEMP\":\"" << (stats.stats_yearly[i].max_temp.mkelvin == 0 ? 0 : get_temperature_string(stats.stats_yearly[i].max_temp)) << "\",";
 			out << "},";
-			total_stats.selection_size += stats_yearly[i].selection_size;
-			total_stats.total_time.seconds += stats_yearly[i].total_time.seconds;
+			total_stats.selection_size += stats.stats_yearly[i].selection_size;
+			total_stats.total_time.seconds += stats.stats_yearly[i].total_time.seconds;
 			i++;
 		}
 		exportHTMLstatisticsTotal(out, &total_stats);
diff --git a/core/statistics.c b/core/statistics.c
index b25080a9f..b7e4e1f4c 100644
--- a/core/statistics.c
+++ b/core/statistics.c
@@ -3,7 +3,7 @@
  *
  * core logic for the Info & Stats page -
  * char *get_minutes(int seconds);
- * void process_all_dives();
+ * void calculate_stats_summary(struct stats_summary *out);
  */
 #include "gettext.h"
 #include <string.h>
@@ -14,12 +14,7 @@
 #include "divelist.h"
 #include "statistics.h"
 
-static stats_t stats;
 stats_t stats_selection;
-stats_t *stats_monthly = NULL;
-stats_t *stats_yearly = NULL;
-stats_t *stats_by_trip = NULL;
-stats_t *stats_by_type = NULL;
 
 static void process_temperatures(struct dive *dp, stats_t *stats)
 {
@@ -91,7 +86,13 @@ char *get_minutes(int seconds)
 	return buf;
 }
 
-void process_all_dives()
+/*
+ * Calculate a summary of the statistics and put in the stats_summary
+ * structure provided in the first parameter.
+ * Before first use, it should be initialized with init_stats_summary().
+ * After use, memory must be released with free_stats_summary().
+ */
+void calculate_stats_summary(struct stats_summary *out)
 {
 	int idx;
 	struct dive *dp;
@@ -104,8 +105,8 @@ void process_all_dives()
 	int trip_iter = 0;
 	dive_trip_t *trip_ptr = 0;
 	unsigned int size, tsize;
+	stats_t stats = { 0 };
 
-	memset(&stats, 0, sizeof(stats));
 	if (dive_table.nr > 0) {
 		stats.shortest_time.seconds = dive_table.dives[0]->duration.seconds;
 		stats.min_depth.mm = dive_table.dives[0]->maxdepth.mm;
@@ -116,37 +117,33 @@ void process_all_dives()
 	 * case (one dive per year or all dives during
 	 * one month) for yearly and monthly statistics*/
 
-	free(stats_yearly);
-	free(stats_monthly);
-	free(stats_by_trip);
-	free(stats_by_type);
-
 	size = sizeof(stats_t) * (dive_table.nr + 1);
 	tsize = sizeof(stats_t) * (NUM_DIVEMODE + 1);
-	stats_yearly = malloc(size);
-	stats_monthly = malloc(size);
-	stats_by_trip = malloc(size);
-	stats_by_type = malloc(tsize);
-	if (!stats_yearly || !stats_monthly || !stats_by_trip || !stats_by_type)
+	free_stats_summary(out);
+	out->stats_yearly = malloc(size);
+	out->stats_monthly = malloc(size);
+	out->stats_by_trip = malloc(size);
+	out->stats_by_type = malloc(tsize);
+	if (!out->stats_yearly || !out->stats_monthly || !out->stats_by_trip || !out->stats_by_type)
 		return;
-	memset(stats_yearly, 0, size);
-	memset(stats_monthly, 0, size);
-	memset(stats_by_trip, 0, size);
-	memset(stats_by_type, 0, tsize);
-	stats_yearly[0].is_year = true;
+	memset(out->stats_yearly, 0, size);
+	memset(out->stats_monthly, 0, size);
+	memset(out->stats_by_trip, 0, size);
+	memset(out->stats_by_type, 0, tsize);
+	out->stats_yearly[0].is_year = true;
 
 	/* Setting the is_trip to true to show the location as first
 	 * field in the statistics window */
-	stats_by_type[0].location = strdup(translate("gettextFromC", "All (by type stats)"));
-	stats_by_type[0].is_trip = true;
-	stats_by_type[1].location = strdup(translate("gettextFromC", divemode_text_ui[OC]));
-	stats_by_type[1].is_trip = true;
-	stats_by_type[2].location = strdup(translate("gettextFromC", divemode_text_ui[CCR]));
-	stats_by_type[2].is_trip = true;
-	stats_by_type[3].location = strdup(translate("gettextFromC", divemode_text_ui[PSCR]));
-	stats_by_type[3].is_trip = true;
-	stats_by_type[4].location = strdup(translate("gettextFromC", divemode_text_ui[FREEDIVE]));
-	stats_by_type[4].is_trip = true;
+	out->stats_by_type[0].location = strdup(translate("gettextFromC", "All (by type stats)"));
+	out->stats_by_type[0].is_trip = true;
+	out->stats_by_type[1].location = strdup(translate("gettextFromC", divemode_text_ui[OC]));
+	out->stats_by_type[1].is_trip = true;
+	out->stats_by_type[2].location = strdup(translate("gettextFromC", divemode_text_ui[CCR]));
+	out->stats_by_type[2].is_trip = true;
+	out->stats_by_type[3].location = strdup(translate("gettextFromC", divemode_text_ui[PSCR]));
+	out->stats_by_type[3].is_trip = true;
+	out->stats_by_type[4].location = strdup(translate("gettextFromC", divemode_text_ui[FREEDIVE]));
+	out->stats_by_type[4].is_trip = true;
 
 	/* this relies on the fact that the dives in the dive_table
 	 * are in chronological order */
@@ -160,20 +157,20 @@ void process_all_dives()
 
 		if (current_year != tm.tm_year) {
 			current_year = tm.tm_year;
-			process_dive(dp, &(stats_yearly[++year_iter]));
-			stats_yearly[year_iter].is_year = true;
+			process_dive(dp, &(out->stats_yearly[++year_iter]));
+			out->stats_yearly[year_iter].is_year = true;
 		} else {
-			process_dive(dp, &(stats_yearly[year_iter]));
+			process_dive(dp, &(out->stats_yearly[year_iter]));
 		}
-		stats_yearly[year_iter].selection_size++;
-		stats_yearly[year_iter].period = current_year;
+		out->stats_yearly[year_iter].selection_size++;
+		out->stats_yearly[year_iter].period = current_year;
 
 		/* stats_by_type[0] is all the dives combined */
-		stats_by_type[0].selection_size++;
-		process_dive(dp, &(stats_by_type[0]));
+		out->stats_by_type[0].selection_size++;
+		process_dive(dp, &(out->stats_by_type[0]));
 
-		process_dive(dp, &(stats_by_type[dp->dc.divemode + 1]));
-		stats_by_type[dp->dc.divemode + 1].selection_size++;
+		process_dive(dp, &(out->stats_by_type[dp->dc.divemode + 1]));
+		out->stats_by_type[dp->dc.divemode + 1].selection_size++;
 
 		if (dp->divetrip != NULL) {
 			if (trip_ptr != dp->divetrip) {
@@ -182,15 +179,15 @@ void process_all_dives()
 			}
 
 			/* stats_by_trip[0] is all the dives combined */
-			stats_by_trip[0].selection_size++;
-			process_dive(dp, &(stats_by_trip[0]));
-			stats_by_trip[0].is_trip = true;
-			stats_by_trip[0].location = strdup(translate("gettextFromC", "All (by trip stats)"));
-
-			process_dive(dp, &(stats_by_trip[trip_iter]));
-			stats_by_trip[trip_iter].selection_size++;
-			stats_by_trip[trip_iter].is_trip = true;
-			stats_by_trip[trip_iter].location = dp->divetrip->location;
+			out->stats_by_trip[0].selection_size++;
+			process_dive(dp, &(out->stats_by_trip[0]));
+			out->stats_by_trip[0].is_trip = true;
+			out->stats_by_trip[0].location = strdup(translate("gettextFromC", "All (by trip stats)"));
+
+			process_dive(dp, &(out->stats_by_trip[trip_iter]));
+			out->stats_by_trip[trip_iter].selection_size++;
+			out->stats_by_trip[trip_iter].is_trip = true;
+			out->stats_by_trip[trip_iter].location = dp->divetrip->location;
 		}
 
 		/* monthly statistics */
@@ -202,14 +199,30 @@ void process_all_dives()
 			if (prev_month != current_month || prev_year != current_year)
 				month_iter++;
 		}
-		process_dive(dp, &(stats_monthly[month_iter]));
-		stats_monthly[month_iter].selection_size++;
-		stats_monthly[month_iter].period = current_month;
+		process_dive(dp, &(out->stats_monthly[month_iter]));
+		out->stats_monthly[month_iter].selection_size++;
+		out->stats_monthly[month_iter].period = current_month;
 		prev_month = current_month;
 		prev_year = current_year;
 	}
 }
 
+void free_stats_summary(struct stats_summary *stats)
+{
+	free(stats->stats_yearly);
+	free(stats->stats_monthly);
+	free(stats->stats_by_trip);
+	free(stats->stats_by_type);
+}
+
+void init_stats_summary(struct stats_summary *stats)
+{
+	stats->stats_yearly = NULL;
+	stats->stats_monthly = NULL;
+	stats->stats_by_trip = NULL;
+	stats->stats_by_type = NULL;
+}
+
 /* make sure we skip the selected summary entries */
 void process_selected_dives(void)
 {
diff --git a/core/statistics.h b/core/statistics.h
index 7766d3154..4639ecf3f 100644
--- a/core/statistics.h
+++ b/core/statistics.h
@@ -12,10 +12,6 @@
 #include "core/units.h"
 #include "core/dive.h"	// For MAX_CYLINDERS
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 typedef struct
 {
 	int period;
@@ -42,13 +38,22 @@ typedef struct
 	char *location;
 } stats_t;
 extern stats_t stats_selection;
-extern stats_t *stats_yearly;
-extern stats_t *stats_monthly;
-extern stats_t *stats_by_trip;
-extern stats_t *stats_by_type;
+
+struct stats_summary {
+	stats_t *stats_yearly;
+	stats_t *stats_monthly;
+	stats_t *stats_by_trip;
+	stats_t *stats_by_type;
+};
+
+#ifdef __cplusplus
+extern "C" {
+#endif
 
 extern char *get_minutes(int seconds);
-extern void process_all_dives();
+extern void init_stats_summary(struct stats_summary *stats);
+extern void free_stats_summary(struct stats_summary *stats);
+extern void calculate_stats_summary(struct stats_summary *stats);
 extern void get_gas_used(struct dive *dive, volume_t gases[MAX_CYLINDERS]);
 extern void process_selected_dives(void);
 void selected_dives_gas_parts(volume_t *o2_tot, volume_t *he_tot);
@@ -57,4 +62,25 @@ void selected_dives_gas_parts(volume_t *o2_tot, volume_t *he_tot);
 }
 #endif
 
+/*
+ * For C++ code, provide a convenience version of stats_summary
+ * that initializes the structure on construction and frees
+ * resources when it goes out of scope. Apart from that, it
+ * can be used as a stats_summary replacement.
+ */
+#ifdef __cplusplus
+struct stats_summary_auto_free : public stats_summary {
+	stats_summary_auto_free();
+	~stats_summary_auto_free();
+};
+inline stats_summary_auto_free::stats_summary_auto_free()
+{
+	init_stats_summary(this);
+}
+inline stats_summary_auto_free::~stats_summary_auto_free()
+{
+	free_stats_summary(this);
+}
+#endif
+
 #endif // STATISTICS_H
diff --git a/desktop-widgets/tab-widgets/maintab.cpp b/desktop-widgets/tab-widgets/maintab.cpp
index ffcb70f5a..25fe34adc 100644
--- a/desktop-widgets/tab-widgets/maintab.cpp
+++ b/desktop-widgets/tab-widgets/maintab.cpp
@@ -424,13 +424,7 @@ void MainTab::updateDiveInfo(bool clear)
 		setEnabled(false);
 	editMode = IGNORE; // don't trigger on changes to the widgets
 
-	// This method updates ALL tabs whenever a new dive or trip is
-	// selected.
-	// If exactly one trip has been selected, we show the location / notes
-	// for the trip in the Info tab, otherwise we show the info of the
-	// selected_dive
 	process_selected_dives();
-	process_all_dives();
 
 	for (auto widget : extraWidgets) {
 		widget->updateData();
diff --git a/desktop-widgets/templatelayout.cpp b/desktop-widgets/templatelayout.cpp
index 0d6586390..5bef7b172 100644
--- a/desktop-widgets/templatelayout.cpp
+++ b/desktop-widgets/templatelayout.cpp
@@ -207,8 +207,10 @@ QString TemplateLayout::generateStatistics()
 	QVariantList years;
 
 	int i = 0;
-	while (stats_yearly != NULL && stats_yearly[i].period) {
-		YearInfo year(stats_yearly[i]);
+	stats_summary_auto_free stats;
+	calculate_stats_summary(&stats);
+	while (stats.stats_yearly != NULL && stats.stats_yearly[i].period) {
+		YearInfo year(stats.stats_yearly[i]);
 		years.append(QVariant::fromValue(year));
 		i++;
 	}
diff --git a/export-html.cpp b/export-html.cpp
index fecbb5235..4907a6bb6 100644
--- a/export-html.cpp
+++ b/export-html.cpp
@@ -49,13 +49,9 @@ int main(int argc, char **argv)
 
 	// this should have set up the informational preferences - let's grab
 	// the units from there
-
 	prefs.unit_system = git_prefs.unit_system;
 	prefs.units = git_prefs.units;
 
-	// populate the statistics
-	process_all_dives();
-
 	// now set up the export settings to create the HTML export
 	struct htmlExportSetting hes;
 	hes.themeFile = "sand.css";
diff --git a/qt-models/yearlystatisticsmodel.cpp b/qt-models/yearlystatisticsmodel.cpp
index 89a6ad0e2..d713be8f1 100644
--- a/qt-models/yearlystatisticsmodel.cpp
+++ b/qt-models/yearlystatisticsmodel.cpp
@@ -176,13 +176,15 @@ void YearlyStatisticsModel::update_yearly_stats()
 {
 	int i, month = 0;
 	unsigned int j, combined_months;
+	stats_summary_auto_free stats;
+	calculate_stats_summary(&stats);
 
-	for (i = 0; stats_yearly != NULL && stats_yearly[i].period; ++i) {
-		YearStatisticsItem *item = new YearStatisticsItem(stats_yearly[i]);
+	for (i = 0; stats.stats_yearly != NULL && stats.stats_yearly[i].period; ++i) {
+		YearStatisticsItem *item = new YearStatisticsItem(stats.stats_yearly[i]);
 		combined_months = 0;
-		for (j = 0; combined_months < stats_yearly[i].selection_size; ++j) {
-			combined_months += stats_monthly[month].selection_size;
-			YearStatisticsItem *iChild = new YearStatisticsItem(stats_monthly[month]);
+		for (j = 0; combined_months < stats.stats_yearly[i].selection_size; ++j) {
+			combined_months += stats.stats_monthly[month].selection_size;
+			YearStatisticsItem *iChild = new YearStatisticsItem(stats.stats_monthly[month]);
 			item->children.append(iChild);
 			iChild->parent = item;
 			month++;
@@ -191,11 +193,10 @@ void YearlyStatisticsModel::update_yearly_stats()
 		item->parent = rootItem.get();
 	}
 
-
-	if (stats_by_trip != NULL && stats_by_trip[0].is_trip == true) {
-		YearStatisticsItem *item = new YearStatisticsItem(stats_by_trip[0]);
-		for (i = 1; stats_by_trip != NULL && stats_by_trip[i].is_trip; ++i) {
-			YearStatisticsItem *iChild = new YearStatisticsItem(stats_by_trip[i]);
+	if (stats.stats_by_trip != NULL && stats.stats_by_trip[0].is_trip == true) {
+		YearStatisticsItem *item = new YearStatisticsItem(stats.stats_by_trip[0]);
+		for (i = 1; stats.stats_by_trip != NULL && stats.stats_by_trip[i].is_trip; ++i) {
+			YearStatisticsItem *iChild = new YearStatisticsItem(stats.stats_by_trip[i]);
 			item->children.append(iChild);
 			iChild->parent = item;
 		}
@@ -204,12 +205,12 @@ void YearlyStatisticsModel::update_yearly_stats()
 	}
 
 	/* Show the statistic sorted by dive type */
-	if (stats_by_type != NULL && stats_by_type[0].selection_size) {
-		YearStatisticsItem *item = new YearStatisticsItem(stats_by_type[0]);
+	if (stats.stats_by_type != NULL && stats.stats_by_type[0].selection_size) {
+		YearStatisticsItem *item = new YearStatisticsItem(stats.stats_by_type[0]);
 		for (i = 1; i <= NUM_DIVEMODE; ++i) {
-			if (stats_by_type[i].selection_size == 0)
+			if (stats.stats_by_type[i].selection_size == 0)
 				continue;
-			YearStatisticsItem *iChild = new YearStatisticsItem(stats_by_type[i]);
+			YearStatisticsItem *iChild = new YearStatisticsItem(stats.stats_by_type[i]);
 			item->children.append(iChild);
 			iChild->parent = item;
 		}