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Plan 9 NeXT

#include "../plan9/lib.h"
#include "../plan9/sys9.h"
#include <signal.h>

/* A stack to hold pcs when signals nest */
#define MAXSIGSTACK 20
typedef struct Pcstack Pcstack;
static struct Pcstack {
	int sig;
	void (*hdlr)(int, char*, Ureg*);
	unsigned long restorepc;
} pcstack[MAXSIGSTACK];
static int nstack = 0;

static void notecont(Ureg*, char*);

void
_notetramp(int sig, void (*hdlr)(int, char*, Ureg*), Ureg *u)
{
	Pcstack *p;

	if(nstack >= MAXSIGSTACK)
		_NOTED(1);	/* nesting too deep; just do system default */
	p = &pcstack[nstack];
	p->restorepc = u->pc;
	p->sig = sig;
	p->hdlr = hdlr;
	nstack++;
	u->pc = (unsigned long) notecont;
	_NOTED(2);	/* NSAVE: clear note but hold state */
}

static void
notecont(Ureg *u, char *s)
{
	Pcstack *p;
	void(*f)(int, char*, Ureg*);

	p = &pcstack[nstack-1];
	f = p->hdlr;
	u->pc = p->restorepc;
	nstack--;
	(*f)(p->sig, s, u);
	_NOTED(3);	/* NRSTR */
}

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