locker.h
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/* GNU Mailutils -- a suite of utilities for electronic mail
Copyright (C) 1999, 2000, 2001, 2005, 2007,
2008 Free Software Foundation, Inc.
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 3 of the License, or (at your option) any later version.
This library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General
Public License along with this library; if not, write to the
Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
Boston, MA 02110-1301 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 */
enum mu_locker_set_mode
{
mu_locker_assign,
mu_locker_set_bit,
mu_locker_clear_bit
};
/* mu_locker_create() flags */
/* Locker types */
#define MU_LOCKER_TYPE_DOTLOCK 0
#define MU_LOCKER_TYPE_EXTERNAL 1
/* 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_TYPE_KERNEL 2
/* Use kernel locking (flock, lockf or ioctl) */
#define MU_LOCKER_TYPE_NULL 3
/* Special locker type: means no lock. This is to be used with
temporary mailboxes stored in memory. */
#define MU_LOCKER_TYPE_TO_FLAG(t) ((t) << 8)
#define MU_LOCKER_FLAG_TO_TYPE(f) ((f) >> 8)
#define MU_LOCKER_IS_TYPE(f,t) (MU_LOCKER_FLAG_TO_TYPE(f) == (t))
#define MU_LOCKER_SET_TYPE(f,t) ((f) = MU_LOCKER_TYPE_TO_FLAG(t) | MU_LOCKER_OPTIONS(f))
#define MU_LOCKER_TYPE_MASK 0xff00
#define MU_LOCKER_OPTION_MASK 0x00ff
#define MU_LOCKER_OPTIONS(f) ((f) & MU_LOCKER_OPTION_MASK)
#define MU_LOCKER_NULL MU_LOCKER_TYPE_TO_FLAG(MU_LOCKER_TYPE_NULL)
#define MU_LOCKER_DOTLOCK MU_LOCKER_TYPE_TO_FLAG(MU_LOCKER_TYPE_DOTLOCK)
#define MU_LOCKER_EXTERNAL MU_LOCKER_TYPE_TO_FLAG(MU_LOCKER_TYPE_EXTERNAL)
#define MU_LOCKER_KERNEL MU_LOCKER_TYPE_TO_FLAG(MU_LOCKER_TYPE_KERNEL)
/* Options */
#define MU_LOCKER_SIMPLE 0x0000
/* Just try and dotlock the file, not the default because its usually
better to retry. */
#define MU_LOCKER_RETRY 0x0001
/* 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 0x0002
/* 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 0x0004
/* 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_DEFAULT (MU_LOCKER_DOTLOCK | 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 mu_locker_set_default_flags (int flags, enum mu_locker_set_mode mode);
extern void mu_locker_set_default_retry_timeout (time_t to);
extern void mu_locker_set_default_retry_count (size_t n);
extern void mu_locker_set_default_expire_timeout (time_t t);
extern void mu_locker_set_default_external_program (char *path);
/* A flags of 0 means that the default will be used. */
extern int mu_locker_create (mu_locker_t *, const char *filename, int flags);
extern void mu_locker_destroy (mu_locker_t *);
/* Time is measured in seconds. */
extern int mu_locker_set_flags (mu_locker_t, int);
extern int mu_locker_mod_flags (mu_locker_t locker, int flags,
enum mu_locker_set_mode mode);
extern int mu_locker_set_expire_time (mu_locker_t, int);
extern int mu_locker_set_retries (mu_locker_t, int);
extern int mu_locker_set_retry_sleep (mu_locker_t, int);
extern int mu_locker_set_external (mu_locker_t, const char* program);
extern int mu_locker_get_flags (mu_locker_t, int*);
extern int mu_locker_get_expire_time (mu_locker_t, int*);
extern int mu_locker_get_retries (mu_locker_t, int*);
extern int mu_locker_get_retry_sleep (mu_locker_t, int*);
extern int mu_locker_get_external (mu_locker_t, char**);
enum mu_locker_mode
{
mu_lck_shr, /* Shared (advisory) lock */
mu_lck_exc, /* Exclusive lock */
mu_lck_opt /* Optional lock = shared, if the locker supports it, no
locking otherwise */
};
extern int mu_locker_lock (mu_locker_t);
extern int mu_locker_touchlock (mu_locker_t);
extern int mu_locker_unlock (mu_locker_t);
extern int mu_locker_remove_lock (mu_locker_t);
#ifdef __cplusplus
}
#endif
#endif