locker.h
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/* GNU Mailutils -- a suite of utilities for electronic mail
Copyright (C) 1999, 2000, 2001 Free Software Foundation, Inc.
GNU Mailutils is free software; you can redistribute it and/or modify
it under the terms of the GNU General Library Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
GNU Mailutils 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 Library General Public License for more details.
You should have received a copy of the GNU Library General Public License
along with GNU Mailutils; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
#ifndef _MAILUTILS_LOCKER_H
#define _MAILUTILS_LOCKER_H
#include <mailutils/types.h>
#ifdef __cplusplus
extern "C" {
#endif
/* lock expiry time */
#define MU_LOCKER_EXPIRE_TIME (10 * 60)
#define MU_LOCKER_RETRIES (10)
#define MU_LOCKER_RETRY_SLEEP (1)
#define MU_LOCKER_EXTERNAL_PROGRAM "dotlock"
/* return codes for the external locker */
#define MU_DL_EX_PERM 4 /* insufficient permissions */
#define MU_DL_EX_EXIST 3 /* lock requested, but file is already locked */
#define MU_DL_EX_NEXIST 2 /* unlock requested, but file is not locked */
#define MU_DL_EX_ERROR 1 /* failed due to some other error */
#define MU_DL_EX_OK 0 /* success */
/* locker_create() flags */
#define MU_LOCKER_SIMPLE 0x00
/* Just try and dotlock the file, not the default because its usually
better to retry. */
#define MU_LOCKER_RETRY 0x01
/* This requests that we loop retries times, sleeping retry_sleep
seconds in between trying to obtain the lock before failing with
MU_LOCK_CONFLICT. */
#define MU_LOCKER_TIME 0x02
/* This mode checks the last update time of the lock, then removes
it if older than MU_LOCKER_EXPIRE_TIME. If a client uses this,
then the servers better periodically update the lock on the
file... do they? */
#define MU_LOCKER_PID 0x04
/* PID locking is only useful for programs that aren't using
an external dotlocker, non-setgid programs will use a dotlocker,
which locks and exits imediately. This is a protection against
a server crashing, it's not generally useful. */
#define MU_LOCKER_EXTERNAL 0x08
/* Use an external program to lock the file. This is necessary
for programs having permission to access a file, but do not
have write permission on the directory that contains that file. */
#define MU_LOCKER_NULL 0x10
/* Special locker type: means no lock. This is to be used with
temporary mailboxes stored in memory. */
#define MU_LOCKER_KERNEL 0x20
/* Use kernel locking (flock, lockf or ioctl) */
#define MU_LOCKER_DEFAULT (MU_LOCKER_RETRY)
/* Use these flags for as the default locker flags (the default defaults
* to MU_LOCKER_DEFAULT). A flags of 0 resets the flags back to the
* the default.
*/
extern int locker_set_default_flags __P((int flags));
/* A flags of 0 means that the default will be used. */
extern int locker_create __P ((locker_t *, const char *filename, int flags));
extern void locker_destroy __P ((locker_t *));
/* Time is measured in seconds. */
extern int locker_set_flags __P ((locker_t, int));
extern int locker_set_expire_time __P ((locker_t, int));
extern int locker_set_retries __P ((locker_t, int));
extern int locker_set_retry_sleep __P ((locker_t, int));
extern int locker_set_external __P ((locker_t, const char* program));
extern int locker_get_flags __P ((locker_t, int*));
extern int locker_get_expire_time __P ((locker_t, int*));
extern int locker_get_retries __P ((locker_t, int*));
extern int locker_get_retry_sleep __P ((locker_t, int*));
extern int locker_get_external __P ((locker_t, char**));
extern int locker_lock __P ((locker_t));
extern int locker_touchlock __P ((locker_t));
extern int locker_unlock __P ((locker_t));
extern int locker_remove_lock __P ((locker_t));
#ifdef __cplusplus
}
#endif
#endif