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[dragonfly.git] / lib / libutil / uucplock.c
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1 /*
2 * Copyright (c) 1988, 1993
3 * The Regents of the University of California. All rights reserved.
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 4. Neither the name of the University nor the names of its contributors
14 * may be used to endorse or promote products derived from this software
15 * without specific prior written permission.
17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
29 * $FreeBSD: src/lib/libutil/uucplock.c,v 1.12.2.1 2000/10/09 20:20:52 brian Exp $
30 * $DragonFly: src/lib/libutil/uucplock.c,v 1.6 2007/12/30 13:44:33 matthias Exp $
32 * @(#)uucplock.c 8.1 (Berkeley) 6/6/93
35 #include <sys/types.h>
36 #include <sys/file.h>
38 #include <dirent.h>
39 #include <errno.h>
40 #include <limits.h>
41 #include <paths.h>
42 #include <signal.h>
43 #include <stdio.h>
44 #include <stdlib.h>
45 #include <string.h>
46 #include <unistd.h>
48 #include "libutil.h"
50 #define MAXTRIES 5
52 #define LOCKTMP "LCKTMP..%d"
53 #define LOCKFMT "LCK..%s"
55 #define GORET(level, val) { err = errno; uuerr = (val); \
56 goto __CONCAT(ret, level); }
58 /* Forward declarations */
59 static int put_pid (int fd, pid_t pid);
60 static pid_t get_pid (int fd,int *err);
63 * uucp style locking routines
66 int
67 uu_lock(const char *tty_name)
69 int fd, tmpfd, i;
70 pid_t pid, pid_old;
71 char lckname[PATH_MAX],
72 lcktmpname[PATH_MAX];
73 int err, uuerr;
75 pid = getpid();
76 (void)snprintf(lcktmpname, sizeof(lcktmpname), _PATH_UUCPLOCK LOCKTMP,
77 pid);
78 (void)snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT,
79 tty_name);
80 if ((tmpfd = creat(lcktmpname, 0664)) < 0)
81 GORET(0, UU_LOCK_CREAT_ERR);
83 for (i = 0; i < MAXTRIES; i++) {
84 if (link (lcktmpname, lckname) < 0) {
85 if (errno != EEXIST)
86 GORET(1, UU_LOCK_LINK_ERR);
88 * file is already locked
89 * check to see if the process holding the lock
90 * still exists
92 if ((fd = open(lckname, O_RDONLY)) < 0)
93 GORET(1, UU_LOCK_OPEN_ERR);
95 if ((pid_old = get_pid (fd, &err)) == -1)
96 GORET(2, UU_LOCK_READ_ERR);
98 close(fd);
100 if (kill(pid_old, 0) == 0 || errno != ESRCH)
101 GORET(1, UU_LOCK_INUSE);
103 * The process that locked the file isn't running, so
104 * we'll lock it ourselves
106 (void)unlink(lckname);
107 } else {
108 if (!put_pid (tmpfd, pid))
109 GORET(3, UU_LOCK_WRITE_ERR);
110 break;
113 GORET(1, (i >= MAXTRIES) ? UU_LOCK_TRY_ERR : UU_LOCK_OK);
115 ret3:
116 (void)unlink(lckname);
117 goto ret1;
118 ret2:
119 (void)close(fd);
120 ret1:
121 (void)close(tmpfd);
122 (void)unlink(lcktmpname);
123 ret0:
124 errno = err;
125 return uuerr;
129 uu_lock_txfr(const char *tty_name, pid_t pid)
131 int fd, err;
132 char lckname[PATH_MAX];
134 snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT, tty_name);
136 if ((fd = open(lckname, O_RDWR)) < 0)
137 return UU_LOCK_OWNER_ERR;
138 if (get_pid(fd, &err) != getpid())
139 err = UU_LOCK_OWNER_ERR;
140 else {
141 lseek(fd, 0, SEEK_SET);
142 err = put_pid(fd, pid) ? 0 : UU_LOCK_WRITE_ERR;
144 close(fd);
146 return err;
150 uu_unlock(const char *tty_name)
152 char tbuf[PATH_MAX];
154 (void)snprintf(tbuf, sizeof(tbuf), _PATH_UUCPLOCK LOCKFMT, tty_name);
155 return unlink(tbuf);
158 const char *
159 uu_lockerr(int uu_lockresult)
161 static char errbuf[128];
162 const char *fmt;
164 switch (uu_lockresult) {
165 case UU_LOCK_INUSE:
166 return "device in use";
167 case UU_LOCK_OK:
168 return "";
169 case UU_LOCK_OPEN_ERR:
170 fmt = "open error: %s";
171 break;
172 case UU_LOCK_READ_ERR:
173 fmt = "read error: %s";
174 break;
175 case UU_LOCK_CREAT_ERR:
176 fmt = "creat error: %s";
177 break;
178 case UU_LOCK_WRITE_ERR:
179 fmt = "write error: %s";
180 break;
181 case UU_LOCK_LINK_ERR:
182 fmt = "link error: %s";
183 break;
184 case UU_LOCK_TRY_ERR:
185 fmt = "too many tries: %s";
186 break;
187 case UU_LOCK_OWNER_ERR:
188 fmt = "not locking process: %s";
189 break;
190 default:
191 fmt = "undefined error: %s";
192 break;
195 (void)snprintf(errbuf, sizeof(errbuf), fmt, strerror(errno));
196 return errbuf;
199 static int
200 put_pid(int fd, pid_t pid)
202 char buf[32];
203 int len;
205 len = sprintf (buf, "%10d\n", (int)pid);
206 return write (fd, buf, len) == len;
209 static pid_t
210 get_pid(int fd, int *err)
212 int bytes_read;
213 char buf[32];
214 pid_t pid;
216 bytes_read = read (fd, buf, sizeof (buf) - 1);
217 if (bytes_read > 0) {
218 buf[bytes_read] = '\0';
219 pid = strtol (buf, (char **) NULL, 10);
220 } else {
221 pid = -1;
222 *err = bytes_read ? errno : EINVAL;
224 return pid;
227 /* end of uucplock.c */