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 */
40 unsigned char Resync[HEAD_RESYNC_LEN] = { 0x01, 0xFE };
41 unsigned 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__)
write_fifo(int fifo,char * buf,unsigned int size)49 int write_fifo ( int fifo, char * buf, unsigned int size )
50 #else
51 int 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