xref: /onnv-gate/usr/src/cmd/lp/lib/msgs/write_fifo.c (revision 0:68f95e015346)
1*0Sstevel@tonic-gate /*
2*0Sstevel@tonic-gate  * CDDL HEADER START
3*0Sstevel@tonic-gate  *
4*0Sstevel@tonic-gate  * The contents of this file are subject to the terms of the
5*0Sstevel@tonic-gate  * Common Development and Distribution License, Version 1.0 only
6*0Sstevel@tonic-gate  * (the "License").  You may not use this file except in compliance
7*0Sstevel@tonic-gate  * with the License.
8*0Sstevel@tonic-gate  *
9*0Sstevel@tonic-gate  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
10*0Sstevel@tonic-gate  * or http://www.opensolaris.org/os/licensing.
11*0Sstevel@tonic-gate  * See the License for the specific language governing permissions
12*0Sstevel@tonic-gate  * and limitations under the License.
13*0Sstevel@tonic-gate  *
14*0Sstevel@tonic-gate  * When distributing Covered Code, include this CDDL HEADER in each
15*0Sstevel@tonic-gate  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
16*0Sstevel@tonic-gate  * If applicable, add the following below this CDDL HEADER, with the
17*0Sstevel@tonic-gate  * fields enclosed by brackets "[]" replaced with your own identifying
18*0Sstevel@tonic-gate  * information: Portions Copyright [yyyy] [name of copyright owner]
19*0Sstevel@tonic-gate  *
20*0Sstevel@tonic-gate  * CDDL HEADER END
21*0Sstevel@tonic-gate  */
22*0Sstevel@tonic-gate /*	Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T	*/
23*0Sstevel@tonic-gate /*	  All Rights Reserved  	*/
24*0Sstevel@tonic-gate 
25*0Sstevel@tonic-gate 
26*0Sstevel@tonic-gate #ident	"%Z%%M%	%I%	%E% SMI"	/* SVr4.0 1.10	*/
27*0Sstevel@tonic-gate /* LINTLIBRARY */
28*0Sstevel@tonic-gate 
29*0Sstevel@tonic-gate # include	<unistd.h>
30*0Sstevel@tonic-gate # include	<errno.h>
31*0Sstevel@tonic-gate # include	<string.h>
32*0Sstevel@tonic-gate 
33*0Sstevel@tonic-gate # include	"lp.h"
34*0Sstevel@tonic-gate # include	"msgs.h"
35*0Sstevel@tonic-gate 
36*0Sstevel@tonic-gate /*
37*0Sstevel@tonic-gate ** Choose at least one byte that won't appear in the body or header
38*0Sstevel@tonic-gate ** of a message.
39*0Sstevel@tonic-gate */
40*0Sstevel@tonic-gate unsigned char	Resync[HEAD_RESYNC_LEN]		= { 0x01, 0xFE };
41*0Sstevel@tonic-gate unsigned char	Endsync[HEAD_RESYNC_LEN]	= { 0x02, 0xFD };
42*0Sstevel@tonic-gate 
43*0Sstevel@tonic-gate 
44*0Sstevel@tonic-gate /*
45*0Sstevel@tonic-gate ** write_fifo() - WRITE A BUFFER WITH HEADER AND CHECKSUM
46*0Sstevel@tonic-gate */
47*0Sstevel@tonic-gate 
48*0Sstevel@tonic-gate #if	defined(__STDC__)
write_fifo(int fifo,char * buf,unsigned int size)49*0Sstevel@tonic-gate int write_fifo ( int fifo, char * buf, unsigned int size )
50*0Sstevel@tonic-gate #else
51*0Sstevel@tonic-gate int write_fifo (fifo, buf, size)
52*0Sstevel@tonic-gate     int			fifo;
53*0Sstevel@tonic-gate     char		*buf;
54*0Sstevel@tonic-gate     unsigned int	size;
55*0Sstevel@tonic-gate #endif
56*0Sstevel@tonic-gate {
57*0Sstevel@tonic-gate     unsigned short	chksum	= 0;
58*0Sstevel@tonic-gate     int			wbytes	= 0;
59*0Sstevel@tonic-gate 
60*0Sstevel@tonic-gate     (void)memcpy (buf + HEAD_RESYNC, Resync, HEAD_RESYNC_LEN);
61*0Sstevel@tonic-gate     (void)memcpy (buf + TAIL_ENDSYNC(size), Endsync, TAIL_ENDSYNC_LEN);
62*0Sstevel@tonic-gate 
63*0Sstevel@tonic-gate     CALC_CHKSUM (buf, size, chksum);
64*0Sstevel@tonic-gate     (void)htos (buf + TAIL_CHKSUM(size), chksum);
65*0Sstevel@tonic-gate 
66*0Sstevel@tonic-gate 
67*0Sstevel@tonic-gate     /*
68*0Sstevel@tonic-gate     ** A message must be written in one call, to avoid interleaving
69*0Sstevel@tonic-gate     ** messages from several processes.
70*0Sstevel@tonic-gate     **
71*0Sstevel@tonic-gate     ** The caller is responsible for trapping SIGPIPE, so
72*0Sstevel@tonic-gate     ** we just return what the "write()" system call does.
73*0Sstevel@tonic-gate     **
74*0Sstevel@tonic-gate     ** Well, almost.  If the pipe was almost full, we may have
75*0Sstevel@tonic-gate     ** written a partial message.  If this is the case, we lie
76*0Sstevel@tonic-gate     ** and say the pipe was full, so the caller can try again.
77*0Sstevel@tonic-gate     **
78*0Sstevel@tonic-gate     ** read_fifo can deal with a truncated message, so we let it
79*0Sstevel@tonic-gate     ** do the grunt work associated with partial messages.
80*0Sstevel@tonic-gate     **
81*0Sstevel@tonic-gate     ** NOTE:  Writing the remainder of the message is not feasible
82*0Sstevel@tonic-gate     ** as someone else may have written something to the fifo
83*0Sstevel@tonic-gate     ** while we were setting up to retry.
84*0Sstevel@tonic-gate     */
85*0Sstevel@tonic-gate 
86*0Sstevel@tonic-gate     if ((wbytes = write(fifo, buf, size)) > 0)
87*0Sstevel@tonic-gate 	if (wbytes != size)
88*0Sstevel@tonic-gate 	    return(0);
89*0Sstevel@tonic-gate 
90*0Sstevel@tonic-gate     return(wbytes);
91*0Sstevel@tonic-gate }
92