sigset.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

#include <signal.h>
#include <errno.h>

/*
 * sigsets are 32-bit longs.  if the 2<<(i-1) bit is on,
 * the signal #define'd as i in signal.h is inluded.
 */

static sigset_t stdsigs = SIGHUP|SIGINT|SIGQUIT|SIGILL|SIGABRT|SIGFPE|SIGKILL|
		SIGSEGV|SIGPIPE|SIGALRM|SIGTERM|SIGUSR1|SIGUSR2;

#define BITSIG(s) (2<<(s))

int
sigemptyset(sigset_t *set)
{
	*set = 0;
	return 0;
}

int
sigfillset(sigset_t *set)
{
	*set = stdsigs;
	return 0;
}

int
sigaddset(sigset_t *set, int signo)
{
	int b;

	b = BITSIG(signo);
	if(!(b&stdsigs)){
		errno = EINVAL;
		return -1;
	}
	*set |= b;
	return 0;
}

int
sigdelset(sigset_t *set, int signo)
{
	int b;

	b = BITSIG(signo);
	if(!(b&stdsigs)){
		errno = EINVAL;
		return -1;
	}
	*set &= ~b;
	return 0;
}

int
sigismember(sigset_t *set, int signo)
{
	int b;

	b = BITSIG(signo);
	if(!(b&stdsigs)){
		errno = EINVAL;
		return -1;
	}
	return (b&*set)? 1 : 0;
}