devcons.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

			}
			qnoblock(kprintoq, 1);
		}else
			qreopen(kprintoq);
		c->iounit = qiomaxatomic;
		break;

	case Qsecstore:
		if(omode == ORDWR)
			error(Eperm);
		if(omode != OREAD)
			memset(secstorebuf, 0, sizeof secstorebuf);
		break;

	case Qsnarf:
		if(omode == ORDWR)
			error(Eperm);
		if(omode == OREAD)
			c->aux = strdup("");
		else
			c->aux = mallocz(SnarfSize, 1);
		break;
	}
	return c;
}

static void
consclose(Chan *c)
{
	switch((ulong)c->qid.path){
	/* last close of control file turns off raw */
	case Qconsctl:
		if(c->flag&COPEN){
			qlock(&kbd.lk);
			if(--kbd.ctl == 0)
				kbd.raw = 0;
			qunlock(&kbd.lk);
		}
		break;

	/* close of kprint allows other opens */
	case Qkprint:
		if(c->flag & COPEN){
			kprintinuse = 0;
			qhangup(kprintoq, nil);
		}
		break;

	case Qsnarf:
		if(c->mode == OWRITE)
			clipwrite(c->aux);
		free(c->aux);
		break;
	}
}

static long
consread(Chan *c, void *buf, long n, vlong off)
{
	char *b;
	char tmp[128];		/* must be >= 6*NUMSIZE */
	char *cbuf = buf;
	int ch, i, eol;
	vlong offset = off;

	if(n <= 0)
		return n;
	switch((ulong)c->qid.path){
	case Qdir:
		return devdirread(c, buf, n, consdir, nelem(consdir), devgen);

	case Qcons:
		qlock(&kbd.lk);
		if(waserror()) {
			qunlock(&kbd.lk);
			nexterror();
		}
		if(kbd.raw) {
			if(qcanread(lineq))
				n = qread(lineq, buf, n);
			else {
				/* read as much as possible */
				do {
					i = qread(kbdq, cbuf, n);
					cbuf += i;
					n -= i;
				} while (n>0 && qcanread(kbdq));
				n = cbuf - (char*)buf;
			}
		} else {
			while(!qcanread(lineq)) {
				qread(kbdq, &kbd.line[kbd.x], 1);
				ch = kbd.line[kbd.x];
				eol = 0;
				switch(ch){
				case '\b':
					if(kbd.x)
						kbd.x--;
					break;
				case 0x15:
					kbd.x = 0;
					break;
				case '\n':
				case 0x04:
					eol = 1;
				default:
					kbd.line[kbd.x++] = ch;
					break;
				}
				if(kbd.x == sizeof(kbd.line) || eol){
					if(ch == 0x04)
						kbd.x--;
					qwrite(lineq, kbd.line, kbd.x);
					kbd.x = 0;
				}
			}
			n = qread(lineq, buf, n);
		}
		qunlock(&kbd.lk);
		poperror();
		return n;

	case Qcpunote:
		sleep(&up->sleep, return0, nil);

	case Qcputime:
		return 0;

	case Qkprint:
		return qread(kprintoq, buf, n);

	case Qpgrpid:
		return readnum((ulong)offset, buf, n, up->pgrp->pgrpid, NUMSIZE);

	case Qpid:
		return readnum((ulong)offset, buf, n, up->pid, NUMSIZE);

	case Qppid:
		return readnum((ulong)offset, buf, n, up->parentpid, NUMSIZE);

	case Qtime:
		return readtime((ulong)offset, buf, n);

	case Qbintime:
		return readbintime(buf, n);

	case Qhostowner:
		return readstr((ulong)offset, buf, n, eve);

	case Qhostdomain:
		return readstr((ulong)offset, buf, n, hostdomain);

	case Quser:
		return readstr((ulong)offset, buf, n, up->user);

	case Qnull:
		return 0;

	case Qsnarf:
		if(offset == 0){
			free(c->aux);
			c->aux = clipread();
		}
		if(c->aux == nil)
			return 0;
		return readstr(offset, buf, n, c->aux);

	case Qsecstore:
		return readstr(offset, buf, n, secstorebuf);

	case Qsysstat:
		return 0;

	case Qswap:
		return 0;

	case Qsysname:
		if(sysname == nil)
			return 0;
		return readstr((ulong)offset, buf, n, sysname);

	case Qrandom:
		return randomread(buf, n);

	case Qdrivers:
		b = malloc(READSTR);
		if(b == nil)
			error(Enomem);
		n = 0;
		for(i = 0; devtab[i] != nil; i++)
			n += snprint(b+n, READSTR-n, "#%C %s\n", devtab[i]->dc,  devtab[i]->name);
		if(waserror()){
			free(b);
			nexterror();
		}
		n = readstr((ulong)offset, buf, n, b);
		free(b);
		poperror();
		return n;

	case Qzero:
		memset(buf, 0, n);
		return n;

	case Qosversion:
		snprint(tmp, sizeof tmp, "2000");
		n = readstr((ulong)offset, buf, n, tmp);
		return n;

	default:
		print("consread 0x%llux\n", c->qid.path);
		error(Egreg);
	}
	return -1;		/* never reached */
}

static long
conswrite(Chan *c, void *va, long n, vlong off)
{
	char buf[256];
	long l, bp;
	char *a = va;
	int fd;
	Chan *swc;
	ulong offset = off;
	Cmdbuf *cb;
	Cmdtab *ct;

	switch((ulong)c->qid.path){
	case Qcons:
		/*
		 * Can't page fault in putstrn, so copy the data locally.
		 */
		l = n;
		while(l > 0){
			bp = l;
			if(bp > sizeof buf)
				bp = sizeof buf;
			memmove(buf, a, bp);
			putstrn0(buf, bp, 1);
			a += bp;
			l -= bp;
		}
		break;

	case Qconsctl:
		if(n >= sizeof(buf))
			n = sizeof(buf)-1;
		strncpy(buf, a, n);
		buf[n] = 0;
		for(a = buf; a;){
			if(strncmp(a, "rawon", 5) == 0){
				qlock(&kbd.lk);
				if(kbd.x){
					qwrite(kbdq, kbd.line, kbd.x);
					kbd.x = 0;
				}
				kbd.raw = 1;
				qunlock(&kbd.lk);
			} else if(strncmp(a, "rawoff", 6) == 0){
				qlock(&kbd.lk);
				kbd.raw = 0;
				kbd.x = 0;
				qunlock(&kbd.lk);
			} else if(strncmp(a, "ctlpon", 6) == 0){
				kbd.ctlpoff = 0;
			} else if(strncmp(a, "ctlpoff", 7) == 0){
				kbd.ctlpoff = 1;
			}
			if((a = strchr(a, ' ')))
				a++;
		}
		break;

	case Qtime:
		if(!iseve())
			error(Eperm);
		return writetime(a, n);

	case Qbintime:
		if(!iseve())
			error(Eperm);
		return writebintime(a, n);

	case Qhostowner:
		return hostownerwrite(a, n);

	case Qhostdomain:
		return hostdomainwrite(a, n);

	case Quser:
		return userwrite(a, n);

	case Qnull:
		break;

	case Qreboot:
		if(!iseve())
			error(Eperm);
		cb = parsecmd(a, n);

		if(waserror()) {
			free(cb);
			nexterror();
		}
		ct = lookupcmd(cb, rebootmsg, nelem(rebootmsg));
		switch(ct->index) {
		case CMreboot:
			rebootcmd(cb->nf-1, cb->f+1);
			break;
		case CMpanic:
			panic("/dev/reboot");
		}
		poperror();
		free(cb);
		break;

	case Qsecstore:
		if(offset >= sizeof secstorebuf || offset+n+1 >= sizeof secstorebuf)
			error(Etoobig);
		secstoretab->qid.vers++;
		memmove(secstorebuf+offset, va, n);
		return n;

	case Qshowfile:
		return showfilewrite(a, n);

	case Qsnarf:
		if(offset >= SnarfSize || offset+n >= SnarfSize)
			error(Etoobig);
		snarftab->qid.vers++;
		memmove((uchar*)c->aux+offset, va, n);
		return n;

	case Qsysstat:
		n = 0;
		break;

	case Qswap:
		if(n >= sizeof buf)
			error(Egreg);
		memmove(buf, va, n);	/* so we can NUL-terminate */
		buf[n] = 0;
		/* start a pager if not already started */
		if(strncmp(buf, "start", 5) == 0){
			kickpager();
			break;
		}
		if(cpuserver && !iseve())
			error(Eperm);
		if(buf[0]<'0' || '9'<buf[0])
			error(Ebadarg);
		fd = strtoul(buf, 0, 0);
		swc = fdtochan(fd, -1, 1, 1);
		setswapchan(swc);
		break;

	case Qsysname:
		if(offset != 0)
			error(Ebadarg);
		if(n <= 0 || n >= sizeof buf)
			error(Ebadarg);
		strncpy(buf, a, n);
		buf[n] = 0;
		if(buf[n-1] == '\n')
			buf[n-1] = 0;
		kstrdup(&sysname, buf);
		break;

	default:
		print("conswrite: 0x%llux\n", c->qid.path);
		error(Egreg);
	}
	return n;
}

Dev consdevtab = {
	'c',
	"cons",

	devreset,
	consinit,
	devshutdown,
	consattach,
	conswalk,
	consstat,
	consopen,
	devcreate,
	consclose,
	consread,
	devbread,
	conswrite,
	devbwrite,
	devremove,
	devwstat,
};

static uvlong uvorder = (uvlong) 0x0001020304050607ULL;

static uchar*
le2vlong(vlong *to, uchar *f)
{
	uchar *t, *o;
	int i;

	t = (uchar*)to;
	o = (uchar*)&uvorder;
	for(i = 0; i < sizeof(vlong); i++)
		t[o[i]] = f[i];
	return f+sizeof(vlong);
}

static uchar*
vlong2le(uchar *t, vlong from)
{
	uchar *f, *o;
	int i;

	f = (uchar*)&from;
	o = (uchar*)&uvorder;
	for(i = 0; i < sizeof(vlong); i++)
		t[i] = f[o[i]];
	return t+sizeof(vlong);
}

static long order = 0x00010203;

static uchar*
le2long(long *to, uchar *f)
{
	uchar *t, *o;
	int i;

	t = (uchar*)to;
	o = (uchar*)&order;
	for(i = 0; i < sizeof(long); i++)
		t[o[i]] = f[i];
	return f+sizeof(long);
}

/*
static uchar*
long2le(uchar *t, long from)
{
	uchar *f, *o;
	int i;

	f = (uchar*)&from;
	o = (uchar*)&order;
	for(i = 0; i < sizeof(long); i++)
		t[i] = f[o[i]];
	return t+sizeof(long);
}
*/

char *Ebadtimectl = "bad time control";

/*
 *  like the old #c/time but with added info.  Return
 *
 *	secs	nanosecs	fastticks	fasthz
 */
static int
readtime(ulong off, char *buf, int n)
{
	vlong	nsec, ticks;
	long sec;
	char str[7*NUMSIZE];

	nsec = todget(&ticks);
	if(fasthz == (vlong)0)
		fastticks((uvlong*)&fasthz);
	sec = nsec/((uvlong) 1000000000);
	snprint(str, sizeof(str), "%*.0lud %*.0llud %*.0llud %*.0llud ",
		NUMSIZE-1, sec,
		VLNUMSIZE-1, nsec,
		VLNUMSIZE-1, ticks,
		VLNUMSIZE-1, fasthz);
	return readstr(off, buf, n, str);
}

/*
 *  set the time in seconds
 */
static int
writetime(char *buf, int n)
{
	char b[13];
	long i;
	vlong now;

	if(n >= sizeof(b))
		error(Ebadtimectl);
	strncpy(b, buf, n);
	b[n] = 0;
	i = strtol(b, 0, 0);
	if(i <= 0)
		error(Ebadtimectl);
	now = i*((vlong) 1000000000);
	todset(now, 0, 0);
	return n;
}

/*
 *  read binary time info.  all numbers are little endian.
 *  ticks and nsec are syncronized.
 */
static int
readbintime(char *buf, int n)
{
	int i;
	vlong nsec, ticks;
	uchar *b = (uchar*)buf;

	i = 0;
	if(fasthz == (vlong)0)
		fastticks((uvlong*)&fasthz);
	nsec = todget(&ticks);
	if(n >= 3*sizeof(uvlong)){
		vlong2le(b+2*sizeof(uvlong), fasthz);
		i += sizeof(uvlong);
	}
	if(n >= 2*sizeof(uvlong)){
		vlong2le(b+sizeof(uvlong), ticks);
		i += sizeof(uvlong);
	}
	if(n >= 8){
		vlong2le(b, nsec);
		i += sizeof(vlong);
	}
	return i;
}

/*
 *  set any of the following
 *	- time in nsec
 *	- nsec trim applied over some seconds
 *	- clock frequency
 */
static int
writebintime(char *buf, int n)
{
	uchar *p;
	vlong delta;
	long period;

	n--;
	p = (uchar*)buf + 1;
	switch(*buf){
	case 'n':
		if(n < sizeof(vlong))
			error(Ebadtimectl);
		le2vlong(&delta, p);
		todset(delta, 0, 0);
		break;
	case 'd':
		if(n < sizeof(vlong)+sizeof(long))
			error(Ebadtimectl);
		p = le2vlong(&delta, p);
		le2long(&period, p);
		todset(-1, delta, period);
		break;
	case 'f':
		if(n < sizeof(uvlong))
			error(Ebadtimectl);
		le2vlong(&fasthz, p);
		todsetfreq(fasthz);
		break;
	}
	return n;
}


int
iprint(char *fmt, ...)
{
	int n, s;
	va_list arg;
	char buf[PRINTSIZE];

	s = splhi();
	va_start(arg, fmt);
	n = vseprint(buf, buf+sizeof(buf), fmt, arg) - buf;
	va_end(arg);
	if(screenputs != nil && iprintscreenputs)
		screenputs(buf, n);
#undef write
	write(2, buf, n);
	splx(s);

	return n;
}