/* signals.c -- Copyright 1988, 1992, 1995 Liam R. E. Quin.
 * All Rights Reserved.
 * This code is NOT in the public domain.
 * See the file COPYRIGHT for full details.
 */

/* $Id: signals.c,v 1.4 1996/08/14 17:01:50 lee Exp $
 * Simple signal handling routines.
 *
 * PORTING NOTES:
 * if there are no errors compiling this file, but signals don't work --
 * e.g. interrupting lqaddfile just stops it with no message, or doesn't
 * stop it at all, see test/signal.c for ideas.
 *
 * If this file does not compile, try
 * 	man 3 sigaction
 * or, if you don't have online man-pages,
 *	grep sigaction /usr/lib/ll* /usr/lib/lint/ll*
 * might work (it might produce binary garbage, though), or
 *	nm /lib/libc.a | grep sigaction
 * In any case, if you find sigaction, leave HAVE_SIGACTION defined in
 * h/globals.h.
 *
 * If you don't find sigaction, you can try to look for sigvec in the same way.
 * If you have sigvec but not sigaction, you want in globals.h
 * (but replace the @-signs with *-signs!):
 * #ifndef HAVE_SIGACTION
 *	/@ #define HAVE_SIGACTION 	Not got that one @@/
 * #endif
 * #ifndef HaVE_SIGVEC
 * # define HAVE_SIGVEC /@ yes, got that one @@/
 * #endif
 *
 * If you are on V7 Unix, an old System V, or 4.1 BSD (!?), you don't have
 * either of these, and must comment out both the HAVE_SIGACTION and the
 * HAVE_SIGVEC lines.  Sorry.
 *
 * If you are on minix, you can implement your own sigaction() :-)
 *
 * Marc Rochkind and Richard Stevens have both written books about
 * Advanced Unix Programming that cover some of this topic.  See them both,
 * as Marc Rochkind's book is out of date and Richard Stevens' only really
 * covers POSIX and SunOS 4.1.
 *
 * In short, V7 Unix signals and old SysV signals cause system calls to be
 * interrupted.  In this case, we warn the user that the index might
 * be broken, and then exit.  One day I might make read, write, etc, calls
 * in liblqtext check for EINTR, in which case we can handle these signals.
 *
 * BSD Signals don't interrupt system calls, or restarts them when it does
 * In this case we have no problem.
 *
 * Newer System V signals are like the BSD ones only incompatible.
 * Again, we can handle them.
 *
 */

#include "globals.h"
#include "emalloc.h"
#include "error.h"

#include <stdio.h>
#include <sys/types.h> /* just in case */
#include <signal.h>

#include "lqutil.h"

#undef SIGFUNCUSED

/* declare SIGTYPE: (see port.h for the definition of SIGTYPEDEF) */
SIGTYPEDEF;

static int
SignalTable[] = { /* (rather short) list of signals to catch */
    SIGINT,
    0
};

void
lqSetSignals(theSignalHandler)
    SIGTYPE theSignalHandler;
{
    static SIGTYPE SafeSignal();
    int i;

    for (i = 0; SignalTable[i] > 0; i++) {
	if (SafeSignal(SignalTable[i], SIG_IGN) != (SIGTYPE) SIG_IGN) {
	    SafeSignal(SignalTable[i], theSignalHandler);
	}
    }
}

#ifdef HAVE_SIGACTION
static SIGTYPE
SafeSignal(Signal, Handler)
    int Signal;
    SIGTYPE Handler;
{
    struct sigaction act, oldact;

    act.sa_handler = Handler;
    sigemptyset(&act.sa_mask);
    act.sa_flags = 0;
# ifdef SA_INTERRUPT
    if (Signal == SIGALRM) {
	act.sa_flags |= SA_INTERRUPT; /* old SunOS (pre Solaris 2.0?) */
    }
# endif

# ifdef SA_RESTART
    if (Signal != SIGALRM) {
	act.sa_flags |= SA_RESTART; /* SysVR4, 4.3+BSD */
    }
#endif

    if (sigaction(Signal, &act, &oldact) < 0) {
#ifdef HAVE_SIGLIST
	extern char *sys_siglist[];

	Error(E_FATAL|E_SYS,
	    "Signal setup for sig%d [%s] failed in sigaction()",
	    Signal,
	    (Signal < NSIG && sys_siglist[Signal]) ?
		sys_siglist[Signal] : "unknown"
	);
#else
	Error(E_FATAL|E_SYS,
	    "Signal setup for sig%d failed in sigaction()",
	    Signal
	);
#endif
    }
    return oldact.sa_handler;
}
# define SIGFUNCUSED "sigaction"
#endif /* HAVE_SIGACTION */

#ifndef SIGFUNCUSED
# ifdef HAVE_SIGVEC
static SIGTYPE
SafeSignal(Signal, Handler)
    int Signal;
    SIGTYPE Handler;
{
    extern  int sigvec(/* sig, vec[], ovec[] */);
    struct sigvec act, oldact;

    act.sv_handler = Handler;
    act.sv_mask = 0;
    act.sv_flags = 0;
# ifdef SA_INTERRUPT
    if (Signal == SIGALRM) {
	act.sv_flags |= SV_INTERRUPT; /* old SunOS (pre Solaris 2.0?) */
    }
# endif

# ifdef SA_RESTART
    if (Signal != SIGALRM) {
	act.sv_flags |= SV_RESTART; /* SysVR4, 4.3+BSD */
    }
#endif

    if (sigvec(Signal, &act, &oldact) < 0) {
#ifdef HAVE_SIGLIST
	extern char *sys_siglist[];

	Error(E_FATAL|E_SYS,
	    "Signal setup for sig%d [%s] failed in sigvec()",
	    Signal,
	    (Signal < NSIG && sys_siglist[Signal]) ?
		sys_siglist[Signal] : "unknown"
	);
#else
	Error(E_FATAL|E_SYS,
	    "Signal setup for sig%d failed in sigvec()",
	    Signal
	);
#endif
    }
    return oldact.sv_handler;
# define SIGFUNCUSED "sigvec"
}
#endif /* HAVE_SIGVEC */
#endif /* SIGFUNCUSED */

#ifndef SIGFUNCUSED
static SIGTYPE
SafeSignal(Signal, Handler)
    int Signal;
    SIGTYPE Handler;
{
    SIGTYPE OldVal;

    if ((OldVal = signal(Signal, Handler)) == (SIGTYPE) -1) {
#ifdef HAVE_SIGLIST
	extern char *sys_siglist[];

	Error(E_FATAL|E_SYS,
	    "Signal setup for sig%d [%s] failed in sigvec()",
	    Signal,
	    (Signal < NSIG && sys_siglist[Signal]) ?
		sys_siglist[Signal] : "unknown"
	);
#else
	Error(E_FATAL|E_SYS,
	    "Signal setup for sig%d failed in sigvec()",
	    Signal
	);
#endif
    }
    return OldVal;
# define SIGFUNCUSED "unreliable-signal"
}
#endif /* SIGFUNCUSED */

static char *
SignalTypeUsed()
{
    return SIGFUNCUSED;
}