Diff: FPointer.h

Revision:

0:fcfb13f40846

Child:

1:d7803001a259

diff -r 000000000000 -r fcfb13f40846 FPointer.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/FPointer.h	Tue Jan 18 17:31:19 2011 +0000
@@ -0,0 +1,137 @@
+/*
+    Copyright (c) 2011 Andy Kirkham
+ 
+    Permission is hereby granted, free of charge, to any person obtaining a copy
+    of this software and associated documentation files (the "Software"), to deal
+    in the Software without restriction, including without limitation the rights
+    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+    copies of the Software, and to permit persons to whom the Software is
+    furnished to do so, subject to the following conditions:
+ 
+    The above copyright notice and this permission notice shall be included in
+    all copies or substantial portions of the Software.
+ 
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+    THE SOFTWARE.
+*/
+
+#ifndef AJK_FPOINTER_H
+#define AJK_FPOINTER_H
+
+namespace AjK {
+
+class FPointerDummy;
+
+/** FPointer - Adds callbacks that take and return a 32bit uint32_t data type.
+ *
+ * The Mbed library supplies a callback using the FunctionPointer object as 
+ * defined in FunctionPointer.h  However, this callback system does not allow
+ * the caller to pass a value to the callback. Likewise, the callback itself
+ * cannot return a value.
+ *
+ * FPointer operates in the same way but allows the callback function to be
+ * passed one arg, a uint32_t value. Additionally, the callback can return
+ * a single uint32_t value. The reason for using uint32_t is that the Mbed
+ * and the microcontroller (LPC1768) have a natural data size of 32bits and
+ * this means we can use the uint32_t as a pointer. See example1.h for more
+ * information. This example passes an "int" by passing a pointer to that
+ * int as a 32bit value. Using this technique you can pass any value you like.
+ * All you have to do is pass a pointer to your value cast to (uint32_t). Your
+ * callback can the deference it to get the original value.
+ *
+ * example2.h shows how to do the same thing but demostrates how to specify
+ * the callback into a class object/method.
+ *
+ * Finally, example3.h shows how to pass multiple values. In this example we
+ * define a data structure and in the callback we pass a pointer to that
+ * data structure thus allowing the callback to again get the values.
+ *
+ * Note, when passing pointers to variables to the callback, if the callback
+ * function/method changes that variables value then it will also change the
+ * value the caller sees. If C pointers are new to you, you are strongly
+ * advised to read up on the subject. It's pointers that often get beginners
+ * into trouble when mis-used.
+ *
+ * @see example1.h
+ * @see example2.h
+ * @see example3.h
+ * @see http://mbed.org/handbook/C-Data-Types
+ * @see http://mbed.org/projects/libraries/svn/mbed/trunk/FunctionPointer.h
+ */
+class FPointer {
+
+protected:
+
+    // C callback function pointer for to pass read data to.
+    uint32_t (*c_callback)(uint32_t); 
+    
+    // C++ callback object/method pointer for to pass read data to.
+    FPointerDummy  *obj_callback;
+    uint32_t (FPointerDummy::*method_callback)(uint32_t);
+
+public:
+    
+    /** Constructor
+     */
+    FPointer() {
+        c_callback      = NULL;
+        obj_callback    = NULL;
+        method_callback = NULL;
+    }
+    
+    /** attach - Overloaded attachment function.
+     *
+     * Attach a C type function pointer as the callback.
+     *
+     * Note, the callback function prototype must be:-
+     * @code
+     * uint32_t myCallbackFunction(uint32_t);
+     * @endcode
+     * @param A C function pointer to call.
+     */
+    void attach(uint32_t (*function)(uint32_t) = 0) { c_callback = function; }
+    
+    /** attach - Overloaded attachment function.
+     *
+     * Attach a C++ type object/method pointer as the callback.
+     *
+     * Note, the callback method prototype must be:-
+     * @code
+     *     public:
+     *         uint32_t myCallbackFunction(uint32_t);
+     * @endcode
+     * @param A C++ object pointer.
+     * @param A C++ method within the object to call.
+     */
+    template<class T> 
+    void attach(T* item, uint32_t (T::*method)(uint32_t)) { 
+        obj_callback    = (FPointerDummy *)item; 
+        method_callback = (uint32_t (FPointerDummy::*)(uint32_t))method; 
+    }
+
+    /** call
+     *
+     * call the callback function.
+     * @param uint32_t The value to pass to the callback.
+     * @return uint32_t The value the callback returns.
+     */
+    uint32_t call(uint32_t arg) {
+        if (c_callback != NULL) return (*c_callback)(arg);
+        else {
+            if (obj_callback  != NULL && method_callback != NULL) 
+                return (obj_callback->*method_callback)(arg);
+        }
+        return 0;
+    }
+};
+
+}; // namespace AjK ends
+
+using namespace AjK;
+
+#endif