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/* dotlock.c - dotfile locking
* Copyright (C) 1998 Free Software Foundation, Inc.
*
* This file is part of GNUPG.
*
* GNUPG 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 of the License, or
* (at your option) any later version.
*
* GNUPG 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 <config.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <ctype.h>
#include "types.h"
#include "util.h"
#include "memory.h"
#if 0
/****************
* Create a lockfile with the given name. A TIMEOUT of 0
* returns immediately, -1 waits forever (hopefully not), other
* values are timeouts in milliseconds.
* Returns: a char pointer used as handle for release lock
* or NULL in case of an error.
*
* Notes: This function creates a lock file in the same directory
* as file_to_lock with the name "file_to_lock.lock"
* A temporary file ".#lk.<pid>.<hostname> is used.
* This function does nothing for Windoze.
*/
const char *
make_dotlock( const char *file_to_lock, long timeout )
{
int rc=-1, fd=-1, pid;
char pidstr[16];
char *tname = NULL;
char *p;
log_debug("dotlock_make: lock='%s'\n", lockfile );
sprintf( pidstr, "%10d\n", getpid() );
/* add the hostname to the second line (FQDN or IP addr?) */
/* create a temporary file */
tname = CreateTmpFile2( p, ".#lk" );
free(p);
if( !tname )
log_fatal( "could not create temporary lock file '%s'\n");
log_debug( "dotlock_make: tmpname='%s'\n", tname );
chmod( tname, 0644 ); /* just in case an umask is set */
if( !(fd = open( tname, O_WRONLY )) )
log_fatal( "could not open temporary lock file '%s'\n", tname);
if( write(fd, pidstr, 11 ) != 11 )
log_fatal( "error writing to temporary lock file '%s'\n", tname);
if( close(fd) ) {
log_fatal( "error closing '%s'\n", tname);
retry:
if( !link(tname, lockfile) )
rc = 0; /* okay */
else if( errno != EEXIST )
log_error( "lock not made: link() failed: %s\n", strerror(errno) );
else { /* lock file already there */
if( (pid = read_lockfile(lockfile)) == -1 ) {
if( errno == ENOENT ) {
log_debug( "lockfile disappeared\n");
goto retry;
}
log_debug("cannot read lockfile\n");
}
else if( pid == getpid() ) {
log_info( "Oops: lock already hold by us\n");
rc = 0; /* okay */
}
else if( kill(pid, 0) && errno == ESRCH ) {
log_info( "removing stale lockfile (created by %d)", (int)pid );
remove( lockfile );
goto retry;
}
log_debug( "lock not made: lock file exists\n" );
}
if( tname ) {
remove(tname);
free(tname);
}
if( !rc )
log_debug( "lock made\n");
return rc;
}
/****************
* Create a lockfile for a existing file
* Returns: a char pointer used as handle for release lock
* or NULL in case of an error.
*
* Notes: This function creates a lock file in the same directory
* as file_to_lock with the name "lock.<inode-no>"
*
* int
* make_inodelock( const char *file_to_lock )
*
*/
/****************
* release a lock
* Returns: 0 := success
*/
int
release_dotlock( const char *lockfile )
{
int pid = read_lockfile( lockfile );
if( pid == -1 ) {
log_error( "release_dotlock: lockfile error");
return -1;
}
if( pid != getpid() ) {
log_error( "release_dotlock: not our lock (pid=%d)", pid);
return -1;
}
if( remove( lockfile ) ) {
log_error( "release_dotlock: error removing lockfile '%s'",
lockfile);
return -1;
}
log_debug( "release_dotlock: released lockfile '%s'", lockfile);
return 0;
}
/****************
* Read the lock file and return the pid, returns -1 on error.
*/
static int
read_lockfile( const char *name )
{
int fd, pid;
char pidstr[16];
if( (fd = open(name, O_RDONLY)) == -1 ) {
int e = errno;
log_debug("error opening lockfile '%s'", name );
errno = e;
return -1;
}
if( read(fd, pidstr, 10 ) != 10 ) {
log_debug("error reading lockfile '%s'", name );
close(fd);
errno = 0;
return -1;
}
close(fd);
pid = atoi(pidstr);
if( !pid || pid == -1 ) {
log_error("invalid pid %d in lockfile '%s'", pid, name );
errno = 0;
return -1;
}
return pid;
}
#endif
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