user/ndblib/read9pmsg.c

/* 
 * 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 <stdlib.h>

#include <stdio.h>
#include <parlib.h>
#include <unistd.h>
#include <signal.h>
#include <fcntl.h>
#include <iplib.h>
#include <fcall.h>
#include <fcallfmt.h>
#include <ndb.h>

long
readn(int f, void *av, long n)
{
	char *a;
	long m, t;

	a = av;
	t = 0;
	while(t < n){
		m = read(f, a+t, n-t);
		if(m <= 0){
			if(t == 0)
				return m;
			break;
		}
		t += m;
	}
	return t;
}

int
read9pmsg(int fd, void *abuf, unsigned int n)
{
	int m, len;
	uint8_t *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;
}