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/*
* File-locking calls
*
* AcquireLock() - acquire an exclusive lock on an open file
* ReleaseLock() - release a lock on an open file
*
* The argument to both calls is a FILE *
*/
#if !HAS_FCNTL && !HAS_FLOCK
*** error -- neither fcntl() nor flock() are present?
#endif
#include <stdio.h>
#if HAS_FCNTL
#include <fcntl.h>
#endif
#if HAS_FLOCK
#include <sys/file.h>
#endif
#include "portlib.h"
/*
* Some braindamaged systems don't define this in fcntl.h.
*/
#ifndef SEEK_SET
#define SEEK_SET 0
#endif
#if HAS_FCNTL /* fcntl() version of locking functions */
int
AcquireLock (f)
FILE *f;
{
struct flock lock;
int fd;
#ifdef DEBUG
printf ("using fcntl() on fileno %d\n", fileno (f));
#endif
lock.l_type = F_WRLCK;
lock.l_start = 0;
lock.l_whence = SEEK_SET;
lock.l_len = 0;
fd = fileno (f);
if (fcntl (fd, F_SETLK, &lock) == 0)
return (1);
#ifdef DEBUG
perror ("AcquireLock");
#endif
return (0);
}
void
ReleaseLock (f)
FILE *f;
{
struct flock lock;
int fd;
lock.l_type = F_UNLCK;
lock.l_start = 0;
lock.l_whence = SEEK_SET;
lock.l_len = 0;
fd = fileno (f);
(void) fcntl (fd, F_SETLK, &lock);
}
#else
#if HAS_FLOCK /* flock() version of locking functions */
int
AcquireLock (f)
FILE *f;
{
int fd;
#ifdef DEBUG
printf ("using flock() on fileno %d\n", fileno (f));
#endif
fd = fileno (f);
if (flock (fd, LOCK_EX | LOCK_NB) == 0)
return (1);
#ifdef DEBUG
perror ("AcquireLock");
#endif
return (0);
}
void
ReleaseLock (f)
FILE *f;
{
int fd;
fd = fileno (f);
(void) flock (fd, LOCK_UN);
}
#endif /* HAS_FLOCK */
#endif /* HAS_FCNTL */
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