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hooks1.c
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C/C++ Source or Header
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1992-09-04
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2KB
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82 lines
/* hooks1.c
* Simple hook example
* Copyright (C) 1991 Commodore-Amiga, Inc.
*
*/
#include <exec/types.h>
#include <exec/libraries.h>
#include <utility/hooks.h>
#include <clib/exec_protos.h>
#include <clib/utility_protos.h>
extern struct Library *SysBase;
struct Library *UtilityBase;
#define ASM __asm
#define REG(x) register __ ## x
/* This function converts register-parameter Hook calling
* convention into standard C conventions. It requires a C
* compiler that supports registerized parameters, such as
* SAS/C 5.xx or greater.
*/
ULONG ASM
hookEntry(REG(a0) struct Hook *h, REG(a2) VOID *o, REG(a1) VOID *msg)
{
return ((*h->h_SubEntry)(h, o, msg));
}
/* This simple function is used to initialize a Hook */
VOID InitHook (struct Hook *h, ULONG (*func)(), VOID *data)
{
/* Make sure a pointer was passed */
if (h)
{
/* Fill in the Hook fields */
h->h_Entry = (ULONG (*)()) hookEntry;
h->h_SubEntry = func;
h->h_Data = data;
}
}
/* This function only prints out a message to the serial port indicating that
* we are inside the callback function. Note that we cannot use printf() or
* any other functions that use standard I/O with any of the system modules that
* support callback Hooks, because there is no guarantee that there would
* be a valid Output() channel. */
ULONG MyFunction (struct Hook *h, VOID *o, VOID *msg)
{
/* Obtain access to the global data segment */
geta4();
/* Debugging function to send a string to the serial port */
KPrintF("Inside MyFunction()\n");
return (1);
}
int main (int argc, char **argv)
{
struct Hook h;
/* Open the utility library */
if (UtilityBase = OpenLibrary ("utility.library", 36))
{
/* Initialize the callback Hook */
InitHook (&h, MyFunction, NULL);
/* Use the utility library function to invoke the Hook */
CallHookPkt (&h, NULL, NULL);
/* Close utility library now that we're done with it */
CloseLibrary (UtilityBase);
}
else
{
/* Display an error message */
printf ("Couldn't open utility.library\n");
}
}