/*  * This file is part of the UCB release of Plan 9. It is subject to the license * terms in the LICENSE file found in the top-level directory of this * distribution and at http://akaros.cs.berkeley.edu/files/Plan9License. No * part of the UCB release of Plan 9, including this file, may be copied, * modified, propagated, or distributed except according to the terms contained * in the LICENSE file. */ #include <u.h>#include <libc.h>#include <fcall.h> intread9pmsg(int fd, void *abuf, uint n){	int m, len;	uchar *buf; 	buf = abuf; 	/* read count */	m = readn(fd, buf, BIT32SZ);	if(m != BIT32SZ){		if(m < 0)			return -1;		return 0;	} 	len = GBIT32(buf);	if(len <= BIT32SZ || len > n){		werrstr("bad length in 9P2000 message header");		return -1;	}	len -= BIT32SZ;	m = readn(fd, buf+BIT32SZ, len);	if(m < len)		return 0;	return BIT32SZ+m;}