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/*++
/* NAME
/* deliver_flock 3
/* SUMMARY
/* lock open file for mail delivery
/* SYNOPSIS
/* #include <deliver_flock.h>
/*
/* int deliver_flock(fd, lock_style, why)
/* int fd;
/* int lock_style;
/* VSTRING *why;
/* DESCRIPTION
/* deliver_flock() sets one exclusive kernel lock on an open file,
/* for example in order to deliver mail.
/* It performs several non-blocking attempts to acquire an exclusive
/* lock before giving up.
/*
/* Arguments:
/* .IP fd
/* A file descriptor that is associated with an open file.
/* .IP lock_style
/* A locking style defined in myflock(3).
/* .IP why
/* A null pointer, or storage for diagnostics.
/* DIAGNOSTICS
/* deliver_flock() returns -1 in case of problems, 0 in case
/* of success. The reason for failure is returned via the \fIwhy\fR
/* parameter.
/* CONFIGURATION PARAMETERS
/* deliver_lock_attempts, number of locking attempts
/* deliver_lock_delay, time in seconds between attempts
/* sun_mailtool_compatibility, disable kernel locking
/* LICENSE
/* .ad
/* .fi
/* The Secure Mailer license must be distributed with this software.
/* AUTHOR(S)
/* Wietse Venema
/* IBM T.J. Watson Research
/* P.O. Box 704
/* Yorktown Heights, NY 10598, USA
/*--*/
/* System library. */
#include "sys_defs.h"
#include <unistd.h>
/* Utility library. */
#include <vstring.h>
#include <myflock.h>
#include <iostuff.h>
/* Global library. */
#include "mail_params.h"
#include "deliver_flock.h"
/* Application-specific. */
#define MILLION 1000000
/* deliver_flock - lock open file for mail delivery */
int deliver_flock(int fd, int lock_style, VSTRING *why)
{
int i;
for (i = 1; /* void */ ; i++) {
if (myflock(fd, lock_style,
MYFLOCK_OP_EXCLUSIVE | MYFLOCK_OP_NOWAIT) == 0)
return (0);
if (i >= var_flock_tries)
break;
rand_sleep(var_flock_delay * MILLION, var_flock_delay * MILLION / 2);
}
if (why)
vstring_sprintf(why, "unable to lock for exclusive access: %m");
return (-1);
}
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