eipconvtest.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 <u.h>
#include <libc.h>

enum
{
	Isprefix= 16,
};

uchar prefixvals[256] =
{
[0x00] 0 | Isprefix,
[0x80] 1 | Isprefix,
[0xC0] 2 | Isprefix,
[0xE0] 3 | Isprefix,
[0xF0] 4 | Isprefix,
[0xF8] 5 | Isprefix,
[0xFC] 6 | Isprefix,
[0xFE] 7 | Isprefix,
[0xFF] 8 | Isprefix,
};

uchar v4prefix[16] = {
	0, 0, 0, 0,
	0, 0, 0, 0,
	0, 0, 0xff, 0xff,
	0, 0, 0, 0
};

void
hnputl(void *p, ulong v)
{
	uchar *a;

	a = p;
	a[0] = v>>24;
	a[1] = v>>16;
	a[2] = v>>8;
	a[3] = v;
}

int
eipconv(va_list *arg, Fconv *f)
{
	char buf[8*5];
	static char *efmt = "%.2lux%.2lux%.2lux%.2lux%.2lux%.2lux";
	static char *ifmt = "%d.%d.%d.%d";
	uchar *p, ip[16];
	ulong *lp;
	ushort s;
	int i, j, n, eln, eli;

	switch(f->chr) {
	case 'E':		/* Ethernet address */
		p = va_arg(*arg, uchar*);
		sprint(buf, efmt, p[0], p[1], p[2], p[3], p[4], p[5]);
		break;
	case 'I':		/* Ip address */
		p = va_arg(*arg, uchar*);
common:
		if(memcmp(p, v4prefix, 12) == 0)
			sprint(buf, ifmt, p[12], p[13], p[14], p[15]);
		else {
			/* find longest elision */
			eln = eli = -1;
			for(i = 0; i < 16; i += 2){
				for(j = i; j < 16; j += 2)
					if(p[j] != 0 || p[j+1] != 0)
						break;
				if(j > i && j - i > eln){
					eli = i;
					eln = j - i;
				}
			}

			/* print with possible elision */
			n = 0;
			for(i = 0; i < 16; i += 2){
				if(i == eli){
					n += sprint(buf+n, "::");
					i += eln;
					if(i >= 16)
						break;
				} else if(i != 0)
					n += sprint(buf+n, ":");
				s = (p[i]<<8) + p[i+1];
				n += sprint(buf+n, "%ux", s);
			}
		}
		break;
	case 'i':		/* v6 address as 4 longs */
		lp = va_arg(*arg, ulong*);
		for(i = 0; i < 4; i++)
			hnputl(ip+4*i, *lp++);
		p = ip;
		goto common;
	case 'V':		/* v4 ip address */
		p = va_arg(*arg, uchar*);
		sprint(buf, ifmt, p[0], p[1], p[2], p[3]);
		break;
	case 'M':		/* ip mask */
		p = va_arg(*arg, uchar*);

		/* look for a prefix mask */
		for(i = 0; i < 16; i++)
			if(p[i] != 0xff)
				break;
		if(i < 16){
			if((prefixvals[p[i]] & Isprefix) == 0)
				goto common;
			for(j = i+1; j < 16; j++)
				if(p[j] != 0)
					goto common;
			n = 8*i + (prefixvals[p[i]] & ~Isprefix);
		} else
			n = 8*16;

		/* got one, use /xx format */
		sprint(buf, "/%d", n);
		break;
	default:
		strcpy(buf, "(eipconv)");
	}
	strconv(buf, f);
	return sizeof(uchar*);
}

uchar testvec[11][16] =
{
 { 0,0,0,0, 0,0,0,0, 0,0,0xff,0xff, 1,3,4,5, },
 { 0xff,0xff,0xff,0xff, 0xff,0xff,0xff,0xff, 0xff,0xff,0xff,0xff, 0xff,0xff,0xff,0xff, },
 { 0xff,0xff,0x80,0, 0,0,0,0, 0,0,0,0, 0,0,0,0, },
 { 0xff,0xff,0xff,0xc0, 0,0,0,0, 0,0,0,0, 0,0,0,0, },
 { 0xff,0xff,0xff,0xff, 0xe0,0,0,0, 0,0,0,0, 0,0,0,0, },
 { 0xff,0xff,0xff,0xff, 0xff,0xf0,0,0, 0,0,0,0, 0,0,0,0, },
 { 0xff,0xff,0xff,0xff, 0xff,0xff,0xf8,0, 0,0,0,0, 0,0,0,0, },
 { 0xff,0xff,0xff,0xff, 0xff,0xff,0xff,0xff, 0xff,0xff,0xff,0xff, 0xff,0xff,0xff,0xff, },
 { 0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0, },
 { 0,0,0,0, 0,0x11,0,0, 0,0,0,0, 0,0,0,0, },
 { 0,0,0,0x11, 0,0,0,0, 0,0,0,0, 0,0,0,0x12, },
};

void
main(void)
{
	int i;

	fmtinstall('I', eipconv);
	fmtinstall('M', eipconv);
	for(i = 0; i < 11; i++)
		print("%I\n%M\n", testvec[i], testvec[i]);
	exits(0);
}