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/* $Id: lockfile.C,v 1.4 2001/08/20 19:51:40 dm Exp $ */
/*
*
* Copyright (C) 1999 David Mazieres (dm@uun.org)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2, or (at
* your option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
* USA
*
*/
#include "amisc.h"
bool
stat_unchanged (const struct stat *sb1, const struct stat *sb2)
{
return sb1->st_dev == sb2->st_dev && sb1->st_ino == sb2->st_ino
&& sb1->st_mtime == sb2->st_mtime
#ifdef SFS_HAVE_STAT_ST_MTIMESPEC
&& sb1->st_mtimespec.tv_nsec == sb2->st_mtimespec.tv_nsec
#endif /* SFS_HAVE_STAT_ST_MTIMESPEC */
&& sb1->st_size == sb2->st_size;
}
static bool
checkstat (const str &path, const struct stat &sb)
{
if (!S_ISREG (sb.st_mode))
warn << path << ": not a regular file -- please delete\n";
else if (sb.st_nlink > 1)
warn << path << ": too many links -- please delete\n";
else if (sb.st_mode & 07177)
warn ("%s: mode 0%o should be 0600 -- please delete\n",
path.cstr (), sb.st_mode & 07777);
else if (sb.st_size)
warn << path << ": file should be empty -- please delete\n";
else
return true;
return false;
}
lockfile::~lockfile ()
{
if (!ok ())
warn << path << ": stolen lockfile\n";
else
unlink (path);
flock (fd, LOCK_UN);
close (fd);
}
bool
lockfile::ok () const
{
struct stat sb, fsb;
if (stat (path, &sb) < 0 || fstat (fd, &fsb) < 0
|| !stat_unchanged (&sb, &fsb))
return false;
return true;
}
ptr<lockfile>
lockfile::alloc (const str &path, bool wait)
{
struct stat sb, fsb;
errno = 0;
if (lstat (path, &sb) >= 0 && !checkstat (path, sb))
return NULL;
else if (errno && errno != ENOENT) {
warn << path << ": " << strerror (errno) << "\n";
return NULL;
}
int fd;
openit:
/* N.B., 0600 (not 0644) to stop others from wedging us with
* LOCK_SH. Anyone with read permission to a file can flock it
* with LOCK_SH, thereby blocking those with write permission who
* want to lock it with LOCK_EX. */
fd = open (path, O_RDWR|O_CREAT, 0600);
if (fd < 0) {
warn << path << ": " << strerror (errno) << "\n";
return NULL;
}
if (flock (fd, LOCK_EX | (wait ? 0 : LOCK_NB)) < 0) {
close (fd);
if (wait && errno == EINTR)
goto openit;
return NULL;
}
errno = 0;
if (fstat (fd, &fsb) < 0 || !checkstat (path, fsb)) {
if (errno)
warn << "fstat (" << path << "): " << strerror (errno) << "\n";
flock (fd, LOCK_UN);
close (fd);
return NULL;
}
if (lstat (path, &sb) < 0 || !stat_unchanged (&fsb, &sb)) {
flock (fd, LOCK_UN);
close (fd);
goto openit;
}
close_on_exec (fd);
return New refcounted<lockfile> (path, fd);
}
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