_chain_intr

Chains to another interrupt handler.

Defined in header <dos.h>

Syntax

#include <dos.h>
void _chain_intr(void (interrupt far *neivhandler){));

Portability

Remarks

The _chaln_lntr functions passes control from the currently executing interrupt handler to the new interrupt handler whose address is newhandler. The current register set is NOT passed to the new handler. Instead, the new handler receives the registers that were stacked (and possibly modified in the stack) by the old handler. The new handler can simply return, as if it were the original handler. The old handler is not entered again.

The _chain_intr function may be called only by C interrupt functions. It is useful when writing a TSR that needs to insert itself in a chain of interrupt handlers (such as the keyboard interrupt).

Return value

_cliain_intr does not return a value.

See also

• _dos_getvect
• _dos_setvect
• _dos_l<eep

Example

#include <dos.h>
#include <stdio.h>
#include <process.h>

ttifdef  cplusplus
    #def ine _CPPARGS  .. .
#else
    ttdefine _CPPARGS
tendif

typedef void  interrupt (*fptr) (_CPPARGS) ;

static void mesg(char  *s)
{
  while  (*s)
    bdos(2,*s++,0);
}
#pragma argsused
void interrupt handler2 (unsigned bp, unsigned di)
  _enable();
  mesgC'In handler 2.\r\n");
  if  (di == 1)
    mesgC'DI is l\r\n") ;
  else
    mesgC'DI is not  l\r\n");
  di+ + ;

#pragma argsused
void interrupt handlerl (unsigned     unsigned di)

  _enable() ;
  mesgC'In handler  l.\r\n");
  if  (di == 0)
    mesgC'DI is  0\r\n") ;
  else
    mesgC'DI is not ■0\r\n");
  di++;
  mesg("Chaining to handler  2.\r\n");
  _chain_intr (handler2);
}
void mainO
{
  _dos_setvect (128,(fptr) handlerl);
  printf ("About to generate interrupt 128\n");
  _DI = 0;
  geninterrupt (128);
  printf ("DI was 0 before interrupt, is now Ox%x\n",_DI) ;
  exit(0),•

Differences from modern implementations

Nothing recorded yet.

Modern references

• Microsoft C runtime (search)

These are search links, not yet checked by hand.

Extraction notes

• heading `chain intr` read as `_chain_intr`

Stable link: /3.1/dos.h/_chain_intr/ · short form /3.1/_chain_intr/