Add a choice of what messages to preserve to clear()

Author: janakelarsson

src/NB_SMS.cpp

@@ -436,13 +436,15 @@ void NB_SMS::flush()
   }
 }
 
-void NB_SMS::clear()
+void NB_SMS::clear(int flag)
 {
   _ptrUTF8 = "";
 
   while (MODEM.ready() == 0);
 
-  MODEM.sendf("AT+CMGD=0,2");
+  if (flag<1 || flag>4) flag = 2;
+
+  MODEM.sendf("AT+CMGD=0,%d",flag);
 
   if (_synch) {
     MODEM.waitForResponse(55000);

src/NB_SMS.h

@@ -85,8 +85,12 @@ class NB_SMS : public Stream {
   void flush();
 
   /** Delete all read and sent SMS from Modem memory and process answer
+   * flag=1 preserves sent, unsent, and unread messages
+   * flag=2 preserves unsent and unread messages
+   * flag=3 preserves unread messages
+   * flag=4 preserves no messages
    */
-  void clear();
+  void clear(int flag=2);
 
 private:
   bool _synch;