diff --git a/Subsurface-mobile.pro b/Subsurface-mobile.pro
index 5846536ff..b604f4858 100644
--- a/Subsurface-mobile.pro
+++ b/Subsurface-mobile.pro
@@ -75,7 +75,7 @@ SOURCES += subsurface-mobile-main.cpp \
 	core/import-csv.cpp \
 	core/save-html.c \
 	core/statistics.c \
-	core/worldmap-save.c \
+	core/worldmap-save.cpp \
 	core/libdivecomputer.cpp \
 	core/version.c \
 	core/save-git.cpp \
diff --git a/core/CMakeLists.txt b/core/CMakeLists.txt
index 88e1ea312..5e07de60c 100644
--- a/core/CMakeLists.txt
+++ b/core/CMakeLists.txt
@@ -203,7 +203,7 @@ set(SUBSURFACE_CORE_LIB_SRCS
 	windowtitleupdate.cpp
 	windowtitleupdate.h
 	worldmap-options.h
-	worldmap-save.c
+	worldmap-save.cpp
 	worldmap-save.h
 	xmlparams.cpp
 	xmlparams.h
diff --git a/core/worldmap-save.c b/core/worldmap-save.cpp
similarity index 73%
rename from core/worldmap-save.c
rename to core/worldmap-save.cpp
index 61c223442..5f3804a36 100644
--- a/core/worldmap-save.c
+++ b/core/worldmap-save.cpp
@@ -15,21 +15,22 @@
 #include "errorhelper.h"
 #include "file.h"
 #include "save-html.h"
+#include "subsurface-string.h"
 #include "worldmap-save.h"
 #include "worldmap-options.h"
 #include "gettext.h"
 
-char *getGoogleApi()
+static const char *getGoogleApi()
 {
 	/* google maps api auth*/
 	return "https://maps.googleapis.com/maps/api/js?";
 }
 
-void writeMarkers(struct membuffer *b, bool selected_only)
+static void writeMarkers(struct membuffer *b, bool selected_only)
 {
 	int i, dive_no = 0;
 	struct dive *dive;
-	char pre[1000], post[1000];
+	std::string pre, post;
 
 	for_each_dive (i, dive) {
 		if (selected_only) {
@@ -42,13 +43,13 @@ void writeMarkers(struct membuffer *b, bool selected_only)
 		put_degrees(b, ds->location.lat, "temp = new google.maps.Marker({position: new google.maps.LatLng(", "");
 		put_degrees(b, ds->location.lon, ",", ")});\n");
 		put_string(b, "markers.push(temp);\ntempinfowindow = new google.maps.InfoWindow({content: '<div id=\"content\">'+'<div id=\"siteNotice\">'+'</div>'+'<div id=\"bodyContent\">");
-		snprintf(pre, sizeof(pre), "<p>%s ", translate("gettextFromC", "Date:"));
-		put_HTML_date(b, dive, pre, "</p>");
-		snprintf(pre, sizeof(pre), "<p>%s ", translate("gettextFromC", "Time:"));
-		put_HTML_time(b, dive, pre, "</p>");
-		snprintf(pre, sizeof(pre), "<p>%s ", translate("gettextFromC", "Duration:"));
-		snprintf(post, sizeof(post), " %s</p>", translate("gettextFromC", "min"));
-		put_duration(b, dive->duration, pre, post);
+		pre = format_string_std("<p>%s ", translate("gettextFromC", "Date:"));
+		put_HTML_date(b, dive, pre.c_str(), "</p>");
+		pre = format_string_std("<p>%s ", translate("gettextFromC", "Time:"));
+		put_HTML_time(b, dive, pre.c_str(), "</p>");
+		pre = format_string_std("<p>%s ", translate("gettextFromC", "Duration:"));
+		post = format_string_std(" %s</p>", translate("gettextFromC", "min"));
+		put_duration(b, dive->duration, pre.c_str(), post.c_str());
 		put_string(b, "<p> ");
 		put_HTML_quoted(b, translate("gettextFromC", "Max. depth:"));
 		put_HTML_depth(b, dive, " ", "</p>");
@@ -58,12 +59,12 @@ void writeMarkers(struct membuffer *b, bool selected_only)
 		put_string(b, "<p> ");
 		put_HTML_quoted(b, translate("gettextFromC", "Water temp.:"));
 		put_HTML_watertemp(b, dive, " ", "</p>");
-		snprintf(pre, sizeof(pre), "<p>%s <b>", translate("gettextFromC", "Location:"));
-		put_string(b, pre);
+		pre = format_string_std("<p>%s <b>", translate("gettextFromC", "Location:"));
+		put_string(b, pre.c_str());
 		put_HTML_quoted(b, get_dive_location(dive));
 		put_string(b, "</b></p>");
-		snprintf(pre, sizeof(pre), "<p> %s ", translate("gettextFromC", "Notes:"));
-		put_HTML_notes(b, dive, pre, " </p>");
+		pre = format_string_std("<p> %s ", translate("gettextFromC", "Notes:"));
+		put_HTML_notes(b, dive, pre.c_str(), " </p>");
 		put_string(b, "</p>'+'</div>'+'</div>'});\ninfowindows.push(tempinfowindow);\n");
 		put_format(b, "google.maps.event.addListener(markers[%d], 'mouseover', function() {\ninfowindows[%d].open(map,markers[%d]);}", dive_no, dive_no, dive_no);
 		put_format(b, ");google.maps.event.addListener(markers[%d], 'mouseout', function() {\ninfowindows[%d].close();});\n", dive_no, dive_no);
@@ -71,19 +72,19 @@ void writeMarkers(struct membuffer *b, bool selected_only)
 	}
 }
 
-void insert_html_header(struct membuffer *b)
+static void insert_html_header(struct membuffer *b)
 {
 	put_string(b, "<!DOCTYPE html>\n<html>\n<head>\n");
 	put_string(b, "<meta name=\"viewport\" content=\"initial-scale=1.0, user-scalable=no\" />\n<title>World Map</title>\n");
 	put_string(b, "<meta charset=\"UTF-8\">");
 }
 
-void insert_css(struct membuffer *b)
+static void insert_css(struct membuffer *b)
 {
 	put_format(b, "<style type=\"text/css\">%s</style>\n", css);
 }
 
-void insert_javascript(struct membuffer *b, const bool selected_only)
+static void insert_javascript(struct membuffer *b, const bool selected_only)
 {
 	put_string(b, "<script type=\"text/javascript\" src=\"");
 	put_string(b, getGoogleApi());
@@ -97,7 +98,7 @@ void insert_javascript(struct membuffer *b, const bool selected_only)
 	put_string(b, "google.maps.event.addDomListener(window, 'load', initialize);</script>\n");
 }
 
-void export(struct membuffer *b, const bool selected_only)
+static void export_doit(struct membuffer *b, const bool selected_only)
 {
 	insert_html_header(b);
 	insert_css(b);
@@ -105,12 +106,12 @@ void export(struct membuffer *b, const bool selected_only)
 	put_string(b, "\t</head>\n<body>\n<div id=\"map-canvas\"></div>\n</body>\n</html>");
 }
 
-void export_worldmap_HTML(const char *file_name, const bool selected_only)
+extern "C" void export_worldmap_HTML(const char *file_name, const bool selected_only)
 {
 	FILE *f;
 
-	struct membuffer buf = { 0 };
-	export(&buf, selected_only);
+	struct membufferpp buf;
+	export_doit(&buf, selected_only);
 
 	f = subsurface_fopen(file_name, "w+");
 	if (!f) {
@@ -119,5 +120,4 @@ void export_worldmap_HTML(const char *file_name, const bool selected_only)
 		flush_buffer(&buf, f); /*check for writing errors? */
 		fclose(f);
 	}
-	free_buffer(&buf);
 }