rougie
Joined: 14 Jun 2006
Posts: 31
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| Help for compiler error! |
 Posted: Tue Jan 20, 2009 1:03 pm |
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Hello, please consider the following code:
| Code: |
=================================== krn.h
typedef long *LRESULT;
typedef long WPARAM;
typedef long LPARAM;
typedef struct tagHwnd{
void *handle;
} HWND;
typedef LRESULT (*WNDPROC)(HWND, long, WPARAM, LPARAM);
typedef struct tagWnd{
WNDPROC lpfnWndProc;
int style;
long backGround;
long titleMsg;
long extra;
} WND, *pWND;
typedef struct tagRwp{
HWND hwnd;
int showWinEnable;
} RWP;
typedef struct tagMsg{
HWND hwnd;
long msg;
WPARAM wParam;
LPARAM lParam;
long time;
} KM_MSG, *pKM_MSG;
RWP rwp[3] = {0,0,0,0,0,0};
void ULC_KERNEL_dispatch_message(KM_MSG *K);
================================krn.c
#include <Dv4685.h> // DEVICE INNITIALIZATIONS
#include <stdlib.h> // CCS LIBRARY STANDARD LIBRARY
#include <KERNEL.h> // KERNEL HEADER FILE!
LRESULT KWP(HWND x, long m, WPARAM w, LPARAM l);
LRESULT callerFunction(LRESULT (*WNDPROC) (HWND, long, WPARAM,
LPARAM), HWND h, long m, WPARAM w, LPARAM l);
void main()
{
KM_MSG u; // Create an KM_MSG object
pKM_MSG msg = &u; // Assign the address of a KM_MSG object to a pKM_MSG pointer object
WND wnd; // Create a WND object
// DEFINE A WINDOW!
wnd.lpfnWndProc = KWP; // Assign a function pointer ! (Assigns the pointer to a function called KWP !!! )
wnd.style = 0; // Assign other stuff...
wnd.backGround = 0; // Assign other stuff...
wnd.titleMsg = 0; // Assign other stuff...
wnd.extra = 0; // Assign other stuff...
// Assign the address of a wnd object to the void pointer called "handle"
//which is a member of tagHwnd structure
(rwp[0].hwnd).handle = &wnd;
msg->hwnd = rwp[0].hwnd; // Assign a hwnd to another hwnd
ULC_KERNEL_dispatch_message(msg); // Pass a pointer to a msg object
}
void ULC_KERNEL_dispatch_message(KM_MSG *msg)
{
LRESULT zzz;
// Call the correct function based on the contents of the function pointer
// stored in "lpfnWndProc"
zzz = callerFunction(( (struct tagWnd*) (msg->hwnd).handle)->lpfnWndProc, msg->hwnd, msg->msg, msg->wParam, msg->lParam);
}
//CALLBACK FUNCTION IMPLEMENTATION
LRESULT callerFunction(LRESULT(*WNDPROC)(HWND, long, WPARAM, LPARAM) ,HWND h, long m, WPARAM w, LPARAM l)
{
WNDPROC (h, m, w, l);
return 0;
}
LRESULT KWP(HWND x, long m, WPARAM w, LPARAM l)
{
//... other code ...
return 0;
} |
Errors do occur at compile time!
In reference to the sample code above, here is what I am trying to do:
================================
It is important to notice that I have defined a tagHwnd structure, like this:
| Code: | typedef struct tagHwnd{
void *handle;
} HWND; |
And It is also important to knowthat I have also defined an array of tagRWP structures where each element of the array contains an HWND and an showWinEnable member, like this:
| Code: |
typedef struct tagRwp{
HWND hwnd;
int showWinEnable;
} RWP;
RWP rwp[3] = {0,0,0,0,0,0};
|
Basically what I am trying to do is, in main(), assign any function name to the lpfnWndProc member of a WND, like this:
//The following line could assign any function name.
| Code: |
wnd.lpfnWndProc = KWP; // <<< Right now we are using KWP |
So if we want to reference the value in the “handle” member via the rwp[] array, we need to do this:
| Code: | | (rwp[0].hwnd).handle |
So getting back to what I was saying, Once I assigned function KWP to lpfnWndProc I then store the address of the WND object to the void pointer “handle”, like this.
| Code: | | (rwp[0].hwnd).handle = &wnd; |
Then I assign the hwnd member of the first element of tagRwp structures to a hwnd member in the tagMsg, like this:
| Code: | | msg->hwnd = rwp[0].hwnd; |
The msg object now has accessibility to the "lpfnWndProc" member stored in the hwnd object. The “lpfnWndProc” member still contains the address of the function which is KWP’s address.
Next I pass the address of the msg object to the following function.
| Code: | | ULC_KERNEL_dispatch_message(msg); |
And therefore we allow the ULC_KERNEL_dispatch_message() function’s implementation to fetch the correct function based on the contents of the function pointer stored in "lpfnWndProc" by executing the following lines:
| Code: | LRESULT zzz;
zzz = callerFunction(((struct tagWnd*) (msg->hwnd).handle)->lpfnWndProc, msg->hwnd, msg->msg, msg->wParam, msg->lParam); |
================================
Anybody experienced enough in using Callback types of functions this way in PICs using CCS ?
Thanking all in advance !
Regards
Roberto |
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