Add timestamp snprintf. Fix bacapp snprintf to account for string size zero behavior of snprintf.

src/bacnet/datetime.c

@@ -1344,6 +1344,30 @@ bool datetime_date_init_ascii(BACNET_DATE *bdate, const char *ascii)
     return status;
 }
 
+/**
+ * @brief Print the date as an ascii string 2021/12/31
+ * @param bdate - pointer to a BACnetDate
+ * @param str - pointer to the string, or NULL for length only
+ * @param str_size - size of the string, or 0 for length only
+ * @return number of characters printed
+ */
+int datetime_date_to_ascii(BACNET_DATE *bdate, char *str, size_t str_size)
+{
+    int str_len = 0;
+
+    if (!bdate) {
+        return 0;
+    }
+    /* 2021/12/31 */
+    str_len = snprintf(str, str_size,
+        "%04u/%02u/%02u",
+        (unsigned)bdate->year,
+        (unsigned)bdate->month,
+        (unsigned)bdate->day);
+
+    return str_len;
+}
+
 /**
  * @brief Parse an ascii string for the time formatted 23:59:59.99
  * @param btime - #BACNET_TIME structure
@@ -1381,6 +1405,31 @@ bool datetime_time_init_ascii(BACNET_TIME *btime, const char *ascii)
     return status;
 }
 
+/**
+ * @brief Print the time as an ascii string 23:59:59.99
+ * @param btime - pointer to a BACnetTime
+ * @param str - pointer to the string, or NULL for length only
+ * @param str_size - size of the string, or 0 for length only
+ * @return number of characters printed
+ */
+int datetime_time_to_ascii(BACNET_TIME *btime, char *str, size_t str_size)
+{
+    int str_len = 0;
+
+    if (!btime) {
+        return 0;
+    }
+    /* 23:59:59.99 */
+    str_len = snprintf(str, str_size,
+        "%02u:%02u:%02u.%02u",
+        (unsigned)btime->hour,
+        (unsigned)btime->min,
+        (unsigned)btime->sec,
+        (unsigned)btime->hundredths);
+
+    return str_len;
+}
+
 /**
  * @brief Parse an ascii string for the date+time 2021/12/31 23:59:59.99
  * @param bdate - #BACNET_DATE_TIME structure
@@ -1394,7 +1443,7 @@ bool datetime_init_ascii(BACNET_DATE_TIME *bdatetime, const char *ascii)
     int hour = 0, min = 0, sec = 0, hundredths = 0;
     int count = 0;
 
-    count = sscanf(ascii, "%4d/%3d/%3d %3d:%3d:%3d.%3d", &year, &month, &day,
+    count = sscanf(ascii, "%4d/%3d/%3d-%3d:%3d:%3d.%3d", &year, &month, &day,
         &hour, &min, &sec, &hundredths);
     if (count >= 3) {
         datetime_set_date(