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flock.c
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C/C++ Source or Header
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1996-10-15
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3KB
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89 lines
/*
* Program: File lock
*
* Author: Mark Crispin
* Networks and Distributed Computing
* Computing & Communications
* University of Washington
* Administration Building, AG-44
* Seattle, WA 98195
* Internet: MRC@CAC.Washington.EDU
*
* Date: 1 August 1988
* Last Edited: 12 October 1996
*
* Copyright 1996 by the University of Washington
*
* Permission to use, copy, modify, and distribute this software and its
* documentation for any purpose and without fee is hereby granted, provided
* that the above copyright notice appears in all copies and that both the
* above copyright notice and this permission notice appear in supporting
* documentation, and that the name of the University of Washington not be
* used in advertising or publicity pertaining to distribution of the software
* without specific, written prior permission. This software is made available
* "as is", and
* THE UNIVERSITY OF WASHINGTON DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED,
* WITH REGARD TO THIS SOFTWARE, INCLUDING WITHOUT LIMITATION ALL IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, AND IN
* NO EVENT SHALL THE UNIVERSITY OF WASHINGTON BE LIABLE FOR ANY SPECIAL,
* INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
* LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, TORT
* (INCLUDING NEGLIGENCE) OR STRICT LIABILITY, ARISING OUT OF OR IN CONNECTION
* WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*
*/
#include <ustat.h>
/* Emulator for BSD flock() call
* Accepts: file descriptor
* operation bitmask
* Returns: 0 if successful, -1 if failure
*/
int bsd_flock (fd,operation)
int fd;
int operation;
{
struct stat sbuf;
struct ustat usbuf;
struct flock fl;
int ret;
char tmp[MAILTMPLEN];
/* lock applies to entire file */
fl.l_whence = fl.l_start = fl.l_len = 0;
fl.l_pid = getpid (); /* shouldn't be necessary */
switch (operation & ~LOCK_NB){/* translate to fcntl() operation */
case LOCK_EX: /* exclusive */
fl.l_type = F_WRLCK;
break;
case LOCK_SH: /* shared */
fl.l_type = F_RDLCK;
break;
case LOCK_UN: /* unlock */
fl.l_type = F_UNLCK;
break;
default: /* default */
errno = EINVAL;
return -1;
}
/* ftinode should be -1 if NFS */
if ((!fstat (fd,&sbuf) && !ustat (sbuf.st_dev,&usbuf) && !++usbuf.f_tinode)||
mail_parameters (NIL,GET_DISABLEFCNTLLOCK,NIL))
ret = 0; /* NFS or locking disabled */
else while (ret = fcntl (fd,(operation & LOCK_NB) ? F_SETLK : F_SETLKW,&fl))
if (errno != EINTR) { /* ignore signals */
/* non-blocking lock case? */
if ((operation & LOCK_NB) &&
((errno == EWOULDBLOCK) || (errno == EAGAIN) || (errno == EACCES))) {
errno = EWOULDBLOCK; /* canonicalize error */
return -1; /* OK to fail */
}
sprintf (tmp,"Unexpected locking failure %s",strerror (errno));
mm_log (tmp,WARN); /* give the user a warning of what happened */
sleep (5); /* barf */
break;
}
return ret;
}