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DosHoldSignal
#define INCL_DOSSIGNALS
USHORT rc = DosHoldSignal(ActionCode);
USHORT ActionCode; /* Indicate to Disable/Enable Signals */
USHORT rc; /* return code */
Example
The following example illustrates the use of the Ctrl-C (SIGINTR) signal
to signal time-critical events. Process1 invokes process2, which
establishes a signal handler named CtrlC_Handler() and waits, by blocking
on a reserved RAM semaphore, for a signal from process1. A portion of
process2 is immune to signalling.
#define INCL_DOSPROCESS
#define INCL_DOSSIGNALS
#include <os2.h>
#define SLEEPTIME 200L /* Sleep interval */
#define START_PROGRAM "process2.exe" /* Program name */
main()
{
CHAR ObjFail[50];
PSZ Args;
PSZ Envs;
RESULTCODES ReturnCodes;
USHORT rc;
/* Start process2 and check its PID */
if(!(DosExecPgm(ObjFail, /* Object name buffer */
sizeof(ObjFail), /* Length of obj. name buffer */
EXEC_ASYNC, /* Execution flag */
Args, /* Ptr. to argument string */
Envs, /* Ptr. to environment string */
&ReturnCodes, /* Ptr. to resultcodes struct.*/
START_PROGRAM))) /* Name of program file */
printf("Process2 started.\n");
printf("Process2 ID is %d\n", ReturnCodes.codeTerminate);
/* Sleep to give time slice to process2 */
DosSleep(SLEEPTIME); /* Sleep interval */
/*** After process2 sets signal handler, send process2 a signal ***/
if(!(rc = DosSendSignal(ReturnCodes.codeTerminate, /* PID of process2 */
SIG_CTRLC))) /* Signal to send*/
printf("Ctrl-C signal sent from Process1 to Process2.\n");
}
/* ----- process2.c ----- */
#define INCL_DOSPROCESS
#define INCL_DOSSIGNALS
#define INCL_DOSERRORS
#include <os2.h>
#define SLEEPTIME 50L
#define TIMEOUT 5000L
VOID APIENTRY CtrlC_Handler(arg1, arg2) /** Define signal handler **/
USHORT arg1;
USHORT arg2;
{
printf("Handler for Ctrl-C now running.\n");
return;
}
main()
{
ULONG RamSem = 0L; /* Allocate and initialize Ram
Semaphore */
ULONG far *RamSemHandle = &RamSem; /* Ram Semaphore handle */
USHORT rc;
/* Establish signal handler */
if(!(rc=DosSetSigHandler((PFNSIGHANDLER) CtrlC_Handler,
NULL, /* Previous handler - ignored */
NULL, /* Previous action - ignored */
SIGA_ACCEPT, /* Request type */
SIG_CTRLC))) /* Signal number */
printf("Process2 has set Ctrl-C handler.\n");
else
/* Error processing on rc */;
/* Get semaphore for first time */
if(!(rc=DosSemRequest(RamSemHandle, /* Semaphore handle */
TIMEOUT))) /* Timeout interval */
printf("Semaphore obtained.\n");
/*** Disable and then enable signal-handling ***/
if(!(rc=DosHoldSignal(HLDSIG_DISABLE))) /** Action code - disable **/
{
printf("Signalling DISABLED.\n");
/* Do signal-proof work here */
if(!(rc=DosHoldSignal(HLDSIG_ENABLE))) /** Action code - enable **/
printf("Signalling ENABLED.\n");
}
/* At this point, process1 may have sent a Ctrl-C signal. */
/* Try to obtain semaphore again -- resulting in Timeout. */
/* The Timeout, however, may be interrupted by the signal. */
printf("Process2 will now wait on a Ramsem for a while.\n");
if((rc=DosSemRequest(RamSemHandle, /* Semaphore handle */
TIMEOUT)) /* Timeout interval */
== ERROR_INTERRUPT)
printf("Process2 interrupted while waiting, rc is %d.\n", rc);
}
Created using Inf-PHP v.2 (c) 2003 Yuri Prokushev
Created using Inf-HTML v.0.9b (c) 1995 Peter Childs