Add an interface for locating a variable by key.

git-svn-id: https://arducopter.googlecode.com/svn/trunk@1811 f9c3cf11-9bcb-44bc-f272-b75c42450872

libraries/AP_Common/AP_Var.cpp

@@ -159,6 +159,22 @@ AP_Var::find(const char *name)
     return NULL;
 }
 
+// Find a variable by key.
+//
+AP_Var *
+AP_Var::find(Key key)
+{
+    AP_Var  *vp;
+
+    for (vp = first(); vp; vp = vp->next()) {
+
+        if (key == vp->key()) {
+            return vp;
+        }
+    }
+    return NULL;
+}
+
 
 // Save the variable to EEPROM, if supported
 //

libraries/AP_Common/AP_Var.h

@@ -214,6 +214,14 @@ public:
     ///
     static AP_Var *find(const char *name);
 
+    /// Find a variable by key.
+    ///
+    /// @param  key             The key being looked up.
+    /// @return                 A pointer to the variable, or NULL if
+    ///                         it does not exist.
+    ///
+    static AP_Var *find(Key key);
+
     /// Save the current value of the variable to EEPROM.
     ///
     /// This interface works for any subclass that implements