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/*
* SCCS: @(#)sharlock.c 1.3 (98/02/24)
*
* UniSoft Ltd., London, England
*
* (C) Copyright 1996 X/Open Company Limited
*
* All rights reserved. No part of this source code may be reproduced,
* stored in a retrieval system, or transmitted, in any form or by any
* means, electronic, mechanical, photocopying, recording or otherwise,
* except as stated in the end-user licence agreement, without the prior
* permission of the copyright owners.
* A copy of the end-user licence agreement is contained in the file
* Licence which accompanies this distribution.
*
* X/Open and the 'X' symbol are trademarks of X/Open Company Limited in
* the UK and other countries.
*/
#ifndef lint
static char sccsid[] = "@(#)sharlock.c 1.3 (98/02/24) TET3 release 3.3";
#endif
/************************************************************************
SCCS: @(#)sharlock.c 1.3 98/02/24 TETware release 3.3
NAME: sharlock.c
PRODUCT: TETware
AUTHOR: Andrew Dingwall, UniSoft Ltd.
DATE CREATED: October 1996
DESCRIPTION:
tcc action function - create a shared lock
this function moved from tccd/stcc.c to here
MODIFICATIONS:
Andrew Dingwall, UniSoft Ltd., February 1998
Added an extra salt character to the unique file name in order
to enable more processes to share a lock.
************************************************************************/
#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <time.h>
#include <sys/types.h>
#include <sys/stat.h>
# include <unistd.h>
#include "dtmac.h"
#include "dtmsg.h"
#include "error.h"
#include "ltoa.h"
#include "dtetlib.h"
#include "tcclib.h"
#ifdef NEEDsrcFile
static char srcFile[] = __FILE__; /* file name for error reporting */
#endif
/* creation modes for files and directories */
#define FILEMODE \
((mode_t) (S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH))
#define DIRMODE \
((mode_t) (S_IRWXU | S_IRWXG | S_IRWXO))
/*
** tcf_sharelock() - create a file in a lock directory (shared lock)
**
** return ER_OK if successful or other ER_* error code on error
**
** if successful, a pointer to the name of the created lock file
** is returned indirectly through *lnp
**
** a zero timeout means return immediately if the operation fails
** a -ve timeout means try indefinately until a lock is obtained or an
** error occurs
*/
int tcf_sharelock(dir, pid, timeout, lnp)
char *dir, **lnp;
long pid;
int timeout;
{
register time_t start;
register int fd, rc, errsave;
char salt1, salt2;
char pidstr[LNUMSZ];
static char *fname;
static int fnamelen;
/* do a sanity check on the request */
ASSERT(dir && *dir);
/* format the pid string */
(void) sprintf(pidstr, "%05lu", pid);
/* allocate storage for the lock file name */
if (BUFCHK(&fname, &fnamelen, (int) (strlen(dir) + strlen(pidstr)) + 4) < 0)
return(ER_ERR);
/*
** try to make the lock directory if it does not exist already,
** then create a file in the directory
**
** if a file already exists whose name is the same as the
** specified lock directory, sleep a bit and try again
*/
start = time((time_t *) 0);
for (;;) {
if (tet_mkdir(dir, DIRMODE) < 0 && (errsave = errno) != EEXIST) {
if ((rc = tet_maperrno(errsave)) == ER_ERR)
error(errsave, "can't make lock directory",
dir);
return(rc);
}
for (salt1 = 'a'; salt1 <= 'z'; salt1++) {
for (salt2 = 'a'; salt2 <= 'z'; salt2++) {
(void) sprintf(fname, "%s/%s%c%c",
dir, pidstr, salt1, salt2);
if ((fd = OPEN(fname, O_RDONLY | O_CREAT | O_EXCL, FILEMODE)) >= 0 || errno != EEXIST)
break;
}
if (fd >= 0 || errno != EEXIST)
break;
}
if (fd >= 0)
break;
else if (salt1 > 'z') {
error(0, "out of lock file names:", fname);
return(ER_ERR);
}
switch (errsave = errno) {
case ENOTDIR:
case ENOENT:
/* parent dir was a plain file */
if (timeout)
break;
/* else fall through */
default:
/* zero timeout or unexpected error */
if ((rc = tet_maperrno(errsave)) == ER_ERR || timeout != 0)
error(errsave, "can't create shared lock file",
fname);
return(rc);
}
if (timeout > 0 && time((time_t *) 0) > start + timeout)
return(ER_TIMEDOUT);
(void) SLEEP(2);
}
/* all ok so close the file and return success */
(void) CLOSE(fd);
*lnp = fname;
return(ER_OK);
}
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