optimize selectedDivesGasUsed()

-return the result instead of storing in a parameter, we now know that the list
 contains only those results that are generated in the function
-allocate the result with the correct length right from the start
-do not iterate over keys of a map and then do a map lookup to get the value but
 use an iterator that gives us both right from the start
-remove one call alltogether as the results were not used there

Signed-off-by: Rolf Eike Beer <eike@sf-mail.de>

4 files changed, 9 insertions, 22 deletions

diff --git a/core/qthelper.cpp b/core/qthelper.cpp
index 35965208c..9483d9ab5 100644
--- a/core/qthelper.cpp
+++ b/core/qthelper.cpp
@@ -375,7 +375,7 @@ static bool lessThan(const QPair<QString, int> &a, const QPair<QString, int> &b)
 	return a.second < b.second;
 }
 
-void selectedDivesGasUsed(QVector<QPair<QString, int> > &gasUsedOrdered)
+QVector<QPair<QString, int>> selectedDivesGasUsed()
 {
 	int i, j;
 	struct dive *d;
@@ -391,10 +391,13 @@ void selectedDivesGasUsed(QVector<QPair<QString, int> > &gasUsedOrdered)
 				gasUsed[gasName] += diveGases[j].mliter;
 			}
 	}
-	Q_FOREACH(const QString& gas, gasUsed.keys()) {
-		gasUsedOrdered.append(qMakePair(gas, gasUsed[gas]));
-	}
+	QVector<QPair<QString, int>> gasUsedOrdered;
+	gasUsedOrdered.reserve(gasUsed.size());
+	for (auto it = gasUsed.cbegin(); it != gasUsed.cend(); ++it)
+		gasUsedOrdered.append(qMakePair(it.key(), it.value()));
 	std::sort(gasUsedOrdered.begin(), gasUsedOrdered.end(), lessThan);
+
+	return gasUsedOrdered;
 }
 
 QString getUserAgent()
diff --git a/core/qthelper.h b/core/qthelper.h
index cbe2b77f0..3b7ff2c59 100644
--- a/core/qthelper.h
+++ b/core/qthelper.h
@@ -80,7 +80,7 @@ QString get_short_dive_date_string(timestamp_t when);
 QString get_trip_date_string(timestamp_t when, int nr, bool getday);
 QString uiLanguage(QLocale *callerLoc);
 QLocale getLocale();
-void selectedDivesGasUsed(QVector<QPair<QString, int> > &gasUsed);
+QVector<QPair<QString, int>> selectedDivesGasUsed();
 QString getUserAgent();
 QString printGPSCoords(const location_t *loc);
 
diff --git a/desktop-widgets/tab-widgets/TabDiveStatistics.cpp b/desktop-widgets/tab-widgets/TabDiveStatistics.cpp
index dacb01721..0cf3befd2 100644
--- a/desktop-widgets/tab-widgets/TabDiveStatistics.cpp
+++ b/desktop-widgets/tab-widgets/TabDiveStatistics.cpp
@@ -97,10 +97,9 @@ void TabDiveStatistics::updateData()
 		ui->timeLimits->setMinimum("");
 	}
 
-	QVector<QPair<QString, int> > gasUsed;
+	QVector<QPair<QString, int> > gasUsed = selectedDivesGasUsed();
 	QString gasUsedString;
 	volume_t vol;
-	selectedDivesGasUsed(gasUsed);
 	for (int j = 0; j < MAX_CYLINDERS; j++) {
 		if (gasUsed.isEmpty())
 			break;
diff --git a/desktop-widgets/tab-widgets/maintab.cpp b/desktop-widgets/tab-widgets/maintab.cpp
index dbb83f356..d1f13dd13 100644
--- a/desktop-widgets/tab-widgets/maintab.cpp
+++ b/desktop-widgets/tab-widgets/maintab.cpp
@@ -542,21 +542,6 @@ void MainTab::updateDiveInfo(bool clear)
 		int mean[MAX_CYLINDERS], duration[MAX_CYLINDERS];
 		per_cylinder_mean_depth(&displayed_dive, select_dc(&displayed_dive), mean, duration);
 
-		// now let's get some gas use statistics
-		QVector<QPair<QString, int> > gasUsed;
-		QString gasUsedString;
-		volume_t vol;
-		selectedDivesGasUsed(gasUsed);
-		for (int j = 0; j < MAX_CYLINDERS; j++) {
-			if (gasUsed.isEmpty())
-				break;
-			QPair<QString, int> gasPair = gasUsed.last();
-			gasUsed.pop_back();
-			vol.mliter = gasPair.second;
-			gasUsedString.append(gasPair.first).append(": ").append(get_volume_string(vol, true)).append("\n");
-		}
-		if (!gasUsed.isEmpty())
-			gasUsedString.append("...");
 		volume_t o2_tot = {}, he_tot = {};
 		selected_dives_gas_parts(&o2_tot, &he_tot);