git: drawterm

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add dirchanstat() from 9front to handle seek bug

--- a/kern/chan.c

+++ b/kern/chan.c

@@ -1600,3 +1600,42 @@

 		return;

 	error(Enotdir);

 }

+

+

+enum

+{

+	DIRSIZE	= STATFIXLEN + 16 * 4		/* enough for encoded stat buf + some reasonable strings */

+};

+

+Dir*

+dirchanstat(Chan *c)

+{

+	Dir *d;

+	uchar *buf;

+	int n, nd, i;

+

+	nd = DIRSIZE;

+	for(i=0; i<2; i++){	/* should work by the second try */

+		d = smalloc(sizeof(Dir) + BIT16SZ + nd);

+		if(waserror()){

+			free(d);

+			nexterror();

+		}

+		buf = (uchar*)&d[1];

+		n = devtab[c->type]->stat(c, buf, BIT16SZ+nd);

+		if(n < BIT16SZ)

+			error(Eshortstat);

+		nd = GBIT16(buf);	/* upper bound on size of Dir + strings */

+		if(nd <= n){

+			if(convM2D(buf, n, d, (char*)&d[1]) == 0)

+				error(Eshortstat);

+			poperror();

+			return d;

+		}

+		/* else sizeof(Dir)+BIT16SZ+nd is plenty */

+		free(d);

+		poperror();

+	}

+	error(Eshortstat);

+	return nil;

+}

--- a/kern/fns.h

+++ b/kern/fns.h

@@ -50,6 +50,7 @@

 int		devstat(Chan*, uchar*, int, Dirtab*, int, Devgen*);

 Walkqid*	devwalk(Chan*, Chan*, char**, int, Dirtab*, int, Devgen*);

 int		devwstat(Chan*, uchar*, int);

+Dir*		dirchanstat(Chan*);

 void		drawcmap(void);

 Fgrp*		dupfgrp(Fgrp*);

 int		emptystr(char*);

--- a/kern/sysfile.c

+++ b/kern/sysfile.c

@@ -503,9 +503,7 @@

 _sysseek(int fd, vlong off, int whence)

 {

 	Chan *c;

-	uchar buf[sizeof(Dir)+100];

-	Dir dir;

-	int n;

+	Dir *d;

 	c = fdtochan(fd, -1, 1, 1);

 	if(waserror()){

@@ -538,10 +536,9 @@

 	case 2:

 		if(c->qid.type & QTDIR)

 			error(Eisdir);

-		n = devtab[c->type]->stat(c, buf, sizeof buf);

-		if(convM2D(buf, n, &dir, nil) == 0)

-			error("internal error: stat error in seek");

-		off = dir.length + off;

+		d = dirchanstat(c);

+		off = d->length + off;

+		free(d);

 		if(off < 0)

 			error(Enegoff);

 		c->offset = off;

-- 

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