1/*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License, Version 1.0 only
6 * (the "License").  You may not use this file except in compliance
7 * with the License.
8 *
9 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
10 * or http://www.opensolaris.org/os/licensing.
11 * See the License for the specific language governing permissions
12 * and limitations under the License.
13 *
14 * When distributing Covered Code, include this CDDL HEADER in each
15 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
16 * If applicable, add the following below this CDDL HEADER, with the
17 * fields enclosed by brackets "[]" replaced with your own identifying
18 * information: Portions Copyright [yyyy] [name of copyright owner]
19 *
20 * CDDL HEADER END
21 */
22/*	Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T	*/
23/*	  All Rights Reserved  	*/
24
25
26#ident	"%Z%%M%	%I%	%E% SMI"	/* SVr4.0 1.10	*/
27/* LINTLIBRARY */
28
29# include	<unistd.h>
30# include	<errno.h>
31# include	<string.h>
32
33# include	"lp.h"
34# include	"msgs.h"
35
36/*
37** Choose at least one byte that won't appear in the body or header
38** of a message.
39*/
40unsigned char	Resync[HEAD_RESYNC_LEN]		= { 0x01, 0xFE };
41unsigned char	Endsync[HEAD_RESYNC_LEN]	= { 0x02, 0xFD };
42
43
44/*
45** write_fifo() - WRITE A BUFFER WITH HEADER AND CHECKSUM
46*/
47
48#if	defined(__STDC__)
49int write_fifo ( int fifo, char * buf, unsigned int size )
50#else
51int write_fifo (fifo, buf, size)
52    int			fifo;
53    char		*buf;
54    unsigned int	size;
55#endif
56{
57    unsigned short	chksum	= 0;
58    int			wbytes	= 0;
59
60    (void)memcpy (buf + HEAD_RESYNC, Resync, HEAD_RESYNC_LEN);
61    (void)memcpy (buf + TAIL_ENDSYNC(size), Endsync, TAIL_ENDSYNC_LEN);
62
63    CALC_CHKSUM (buf, size, chksum);
64    (void)htos (buf + TAIL_CHKSUM(size), chksum);
65
66
67    /*
68    ** A message must be written in one call, to avoid interleaving
69    ** messages from several processes.
70    **
71    ** The caller is responsible for trapping SIGPIPE, so
72    ** we just return what the "write()" system call does.
73    **
74    ** Well, almost.  If the pipe was almost full, we may have
75    ** written a partial message.  If this is the case, we lie
76    ** and say the pipe was full, so the caller can try again.
77    **
78    ** read_fifo can deal with a truncated message, so we let it
79    ** do the grunt work associated with partial messages.
80    **
81    ** NOTE:  Writing the remainder of the message is not feasible
82    ** as someone else may have written something to the fifo
83    ** while we were setting up to retry.
84    */
85
86    if ((wbytes = write(fifo, buf, size)) > 0)
87	if (wbytes != size)
88	    return(0);
89
90    return(wbytes);
91}
92