added test for date and time, sql read and write functionality

source/core/utils/string.cpp

@@ -18,6 +18,24 @@ std::string to_string(const blob& data) {
   return str;
 }
 
+std::string to_string(const date_type_t &data) {
+  char buf[11]; // "YYYY-MM-DD" + '\0'
+
+  std::snprintf(buf, sizeof(buf), "%04d-%02u-%02u",
+    data.year, static_cast<unsigned>(data.month), static_cast<unsigned>(data.day));
+
+  return buf;
+}
+
+std::string to_string(const time_type_t &data) {
+  char buf[16]; // "HH:MM:SS.ffffff" + '\0'
+
+  std::snprintf(buf, sizeof(buf), "%02u:%02u:%02u.%06u",
+    static_cast<unsigned>(data.hour), static_cast<unsigned>(data.minute), static_cast<unsigned>(data.second), data.microsecond);
+
+  return buf;
+}
+
 size_t split(const std::string &str, char delim, std::vector<std::string> &values)
 {
   std::stringstream ss(str);