AP_Mission: Add a helper to check if a mission contains an item

libraries/AP_Mission/AP_Mission.cpp

@@ -1849,6 +1849,20 @@ const char *AP_Mission::Mission_Command::type() const {
     }
 }
 
+bool AP_Mission::contains_item(MAV_CMD command) const
+{
+    for (int i = 1; i < num_commands(); i++) {
+        Mission_Command tmp;
+        if (!read_cmd_from_storage(i, tmp)) {
+            continue;
+        }
+        if (tmp.id == command) {
+            return true;
+        }
+    }
+    return false;
+}
+
 // singleton instance
 AP_Mission *AP_Mission::_singleton;
 

libraries/AP_Mission/AP_Mission.h

@@ -478,6 +478,9 @@ public:
         return _rsem;
     }
 
+    // returns true if the mission contains the requested items
+    bool contains_item(MAV_CMD command) const;
+
     // user settable parameters
     static const struct AP_Param::GroupInfo var_info[];