An interrupt-driven interface to 4x4 keypad.

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FPointer Class Reference

FPointer Class Reference

FPointer - Adds callbacks that take and return a 32bit uint32_t data type. More...

#include <FPointer.h>

Public Member Functions

 FPointer ()
 Constructor.
void attach (uint32_t(*function)(uint32_t)=0)
 attach - Overloaded attachment function.
template<class T >
void attach (T *item, uint32_t(T::*method)(uint32_t))
 attach - Overloaded attachment function.
uint32_t call (uint32_t arg)
 call - Overloaded callback initiator.
uint32_t call (void)
 call - Overloaded callback initiator.

Protected Attributes

uint32_t(* c_callback )(uint32_t)
 C callback function pointer.
FPointerDummy * obj_callback
 C++ callback object/method pointer (the object part).
uint32_t(FPointerDummy::* method_callback )(uint32_t)
 C++ callback object/method pointer (the method part).

Detailed Description

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 variable's 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 also:
example1.h
example2.h
example3.h
http://mbed.org/handbook/C-Data-Types
http://mbed.org/projects/libraries/svn/mbed/trunk/FunctionPointer.h

Definition at line 66 of file FPointer.h.


Constructor & Destructor Documentation

FPointer (  )

Constructor.

Definition at line 83 of file FPointer.h.


Member Function Documentation

void attach ( uint32_t(*)(uint32_t)  function = 0 )

attach - Overloaded attachment function.

Attach a C type function pointer as the callback.

Note, the callback function prototype must be:-

 uint32_t myCallbackFunction(uint32_t);
Parameters:
AC function pointer to call.

Definition at line 99 of file FPointer.h.

void attach ( T *  item,
uint32_t(T::*)(uint32_t)  method 
)

attach - Overloaded attachment function.

Attach a C++ type object/method pointer as the callback.

Note, the callback method prototype must be:-

     public:
         uint32_t myCallbackFunction(uint32_t);
Parameters:
AC++ object pointer.
AC++ method within the object to call.

Definition at line 114 of file FPointer.h.

uint32_t call ( uint32_t  arg )

call - Overloaded callback initiator.

call the callback function.

Parameters:
uint32_tThe value to pass to the callback.
Returns:
uint32_t The value the callback returns.

Definition at line 126 of file FPointer.h.

uint32_t call ( void   )

call - Overloaded callback initiator.

Call the callback function without passing an argument. The callback itself is passed NULL. Note, the callback prototype should still be uint32_t callback(uint32_t).

Returns:
uint32_t The value the callback returns.

Definition at line 146 of file FPointer.h.


Field Documentation

uint32_t(* c_callback)(uint32_t) [protected]

C callback function pointer.

Definition at line 71 of file FPointer.h.

uint32_t(FPointerDummy::* method_callback)(uint32_t) [protected]

C++ callback object/method pointer (the method part).

Definition at line 77 of file FPointer.h.

FPointerDummy* obj_callback [protected]

C++ callback object/method pointer (the object part).

Definition at line 74 of file FPointer.h.