Diff: ble/FunctionPointerWithContext.h

Revision:

898:838e1375dbaa

Parent:

891:f3144091ae19

Child:

907:8ddab3271c2f

--- a/ble/FunctionPointerWithContext.h	Thu Nov 26 12:52:01 2015 +0000
+++ b/ble/FunctionPointerWithContext.h	Thu Nov 26 12:52:01 2015 +0000
@@ -19,9 +19,8 @@
 
 #include <string.h>
 
-
 /** A class for storing and calling a pointer to a static or member void function
- *  which takes a context.
+ *  that takes a context.
  */
 template <typename ContextType>
 class FunctionPointerWithContext {
@@ -29,56 +28,53 @@
     typedef FunctionPointerWithContext<ContextType> *pFunctionPointerWithContext_t;
     typedef void (*pvoidfcontext_t)(ContextType context);
 
-    /** Create a FunctionPointerWithContext, attaching a static function
+    /** Create a FunctionPointerWithContext, attaching a static function.
      *
-     *  @param function The void static function to attach (default is none)
+     *  @param function The void static function to attach (default is none).
      */
     FunctionPointerWithContext(void (*function)(ContextType context) = NULL) :
-        _function(NULL), _object(NULL), _member(), _membercaller(NULL), _next(NULL) {
+        _function(NULL), _caller(NULL), _next(NULL) {
         attach(function);
     }
 
-    /** Create a FunctionPointerWithContext, attaching a member function
+    /** Create a FunctionPointerWithContext, attaching a member function.
      *
-     *  @param object The object pointer to invoke the member function on (i.e. the this pointer)
-     *  @param function The address of the void member function to attach
+     *  @param object The object pointer to invoke the member function on (the "this" pointer).
+     *  @param function The address of the void member function to attach.
      */
     template<typename T>
     FunctionPointerWithContext(T *object, void (T::*member)(ContextType context)) :
-        _function(NULL), _object(NULL), _member(), _membercaller(NULL), _next(NULL) {
+        _memberFunctionAndPointer(), _caller(NULL), _next(NULL) {
         attach(object, member);
     }
 
-    /** Attach a static function
+    /** Attach a static function.
      *
-     *  @param function The void static function to attach (default is none)
+     *  @param function The void static function to attach (default is none).
      */
     void attach(void (*function)(ContextType context) = NULL) {
         _function = function;
+        _caller = functioncaller;
     }
 
-    /** Attach a member function
+    /** Attach a member function.
      *
-     *  @param object The object pointer to invoke the member function on (i.e. the this pointer)
-     *  @param function The address of the void member function to attach
+     *  @param object The object pointer to invoke the member function on (the "this" pointer).
+     *  @param function The address of the void member function to attach.
      */
     template<typename T>
     void attach(T *object, void (T::*member)(ContextType context)) {
-        _object = static_cast<void *>(object);
-        memcpy(_member, (char *)&member, sizeof(member));
-        _membercaller = &FunctionPointerWithContext::membercaller<T>;
+        _memberFunctionAndPointer._object = static_cast<void *>(object);
+        memcpy(_memberFunctionAndPointer._memberFunction, (char*) &member, sizeof(member));
+        _caller = &FunctionPointerWithContext::membercaller<T>;
     }
 
-    /** Call the attached static or member function; and if there are chained
+    /** Call the attached static or member function; if there are chained
      *  FunctionPointers their callbacks are invoked as well.
-     *  @Note: all chained callbacks stack up; so hopefully there won't be too
+     *  @Note: All chained callbacks stack up, so hopefully there won't be too
      *  many FunctionPointers in a chain. */
     void call(ContextType context) {
-        if (_function) {
-            _function(context);
-        } else if (_object && _membercaller) {
-            _membercaller(_object, _member, context);
-        }
+        _caller(this, context);
 
         /* Propagate the call to next in the chain. */
         if (_next) {
@@ -87,7 +83,7 @@
     }
 
     /**
-     * Setup an external FunctionPointer as a next in the chain of related
+     * Set up an external FunctionPointer as a next in the chain of related
      * callbacks. Invoking call() on the head FunctionPointer will invoke all
      * chained callbacks.
      *
@@ -107,22 +103,52 @@
 
 private:
     template<typename T>
-    static void membercaller(void *object, char *member, ContextType context) {
-        T *o = static_cast<T *>(object);
-        void (T::*m)(ContextType);
-        memcpy((char *)&m, member, sizeof(m));
-        (o->*m)(context);
+    static void membercaller(pFunctionPointerWithContext_t self, ContextType context) {
+        if (self->_memberFunctionAndPointer._object) {
+            T *o = static_cast<T *>(self->_memberFunctionAndPointer._object);
+            void (T::*m)(ContextType);
+            memcpy((char*) &m, self->_memberFunctionAndPointer._memberFunction, sizeof(m));
+            (o->*m)(context);
+        }
+    }
+
+    static void functioncaller(pFunctionPointerWithContext_t self, ContextType context) {
+        if (self->_function) {
+            self->_function(context);
+        }
     }
 
-    void (*_function)(ContextType context);             /**< static function pointer - NULL if none attached */
-    void *_object;                                      /**< object this pointer - NULL if none attached */
-    char _member[16];                                   /**< raw member function pointer storage - converted back by
-                                                         *   registered _membercaller */
-    void (*_membercaller)(void *, char *, ContextType); /**< registered membercaller function to convert back and call
-                                                         *   _member on _object passing the context. */
-    pFunctionPointerWithContext_t _next;                /**< Optional link to make a chain out of functionPointers; this
+    struct MemberFunctionAndPtr {
+        /*
+         * Forward declaration of a class and a member function to this class.
+         * Because the compiler doesn't know anything about the forwarded member
+         * function, it will always use the biggest size and the biggest alignment
+         * that a member function can take for objects of type UndefinedMemberFunction.
+         */
+        class UndefinedClass;
+        typedef void (UndefinedClass::*UndefinedMemberFunction)(ContextType);
+
+        void* _object;
+        union {
+            char _memberFunction[sizeof(UndefinedMemberFunction)];
+            UndefinedMemberFunction _alignment;
+        };
+    };
+
+    union {
+        pvoidfcontext_t _function;                      /**< Static function pointer - NULL if none attached */
+        /**
+         * object this pointer and pointer to member -
+         * _memberFunctionAndPointer._object will be NULL if none attached
+         */
+        MemberFunctionAndPtr _memberFunctionAndPointer;
+    };
+
+    void (*_caller)(FunctionPointerWithContext*, ContextType);
+
+    pFunctionPointerWithContext_t _next;                /**< Optional link to make a chain out of functionPointers. This
                                                          *   allows chaining function pointers without requiring
-                                                         *   external memory to manage the chain. Also refer to
+                                                         *   external memory to manage the chain. Refer to
                                                          *   'CallChain' as an alternative. */
 };