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/* Copyright © 2005-2007 Roger Leigh <rleigh@debian.org>
*
* schroot is free software: you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* schroot 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
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see
* <http://www.gnu.org/licenses/>.
*
*********************************************************************/
#ifndef SBUILD_LOCK_H
#define SBUILD_LOCK_H
#include <sbuild/sbuild-lock.h>
#include <sbuild/sbuild-custom-error.h>
#include <string>
#include <sys/time.h>
#include <fcntl.h>
#include <signal.h>
namespace sbuild
{
/**
* Advisory locking. This class defines a simple interface for
* shared and exclusive locks.
*/
class lock
{
public:
/// Lock type.
enum type
{
LOCK_SHARED = F_RDLCK, ///< A shared (read) lock.
LOCK_EXCLUSIVE = F_WRLCK, ///< An exclusive (write) lock.
LOCK_NONE = F_UNLCK ///< No lock.
};
/// Error codes.
enum error_code
{
TIMEOUT_HANDLER, ///< Failed to set timeout handler.
TIMEOUT_SET, ///< Failed to set timeout.
TIMEOUT_CANCEL, ///< Failed to cancel timeout.
LOCK, ///< Failed to lock file.
UNLOCK, ///< Failed to unlock file.
LOCK_TIMEOUT, ///< Failed to lock file (timed out).
UNLOCK_TIMEOUT, ///< Failed to unlock file (timed out).
DEVICE_LOCK, ///< Failed to lock device.
DEVICE_LOCK_TIMEOUT, ///< Failed to lock device (timed out).
DEVICE_TEST, ///< Failed to test device lock.
DEVICE_UNLOCK, ///< Failed to unlock device.
DEVICE_UNLOCK_TIMEOUT ///< Failed to unlock device (timed out)
};
/// Exception type.
typedef custom_error<error_code> error;
/**
* Acquire a lock.
*
* @param lock_type the type of lock to acquire.
* @param timeout the time in seconds to wait on the lock.
*/
virtual void
set_lock (type lock_type,
unsigned int timeout) = 0;
/**
* Release a lock. This is equivalent to set_lock with a
* lock_type of LOCK_NONE and a timeout of 0.
*/
virtual void
unset_lock () = 0;
protected:
/// The constructor.
lock ();
/// The destructor.
virtual ~lock ();
/**
* Set the SIGALARM handler.
*
* An error will be thrown on failure.
*/
void
set_alarm ();
/**
* Restore the state of SIGALRM prior to starting lock
* acquisition.
*/
void
clear_alarm ();
/**
* Set up an itimer for future expiry. This is used to interrupt
* system calls. This will set a handler for SIGALRM as a side
* effect (using set_alarm).
*
* An error will be thrown on failure.
*
* @param timer the timeout to set.
*/
void
set_timer (struct itimerval const& timer);
/**
* Remove any itimer currently set up. This will clear any
* SIGALRM handler (using clear_alarm).
*
* An error will be thrown on failure.
*/
void
unset_timer ();
private:
/// Signals saved during timeout.
struct sigaction saved_signals;
};
/**
* File lock. Simple whole-file shared and exclusive advisory
* locking based upon POSIX fcntl byte region locks.
*/
class file_lock : public lock
{
public:
/**
* The constructor.
*
* @param fd the file descriptor to lock.
*/
file_lock (int fd);
/// The destructor.
virtual ~file_lock ();
virtual void
set_lock (lock::type lock_type,
unsigned int timeout);
virtual void
unset_lock ();
private:
/// The file descriptor to lock.
int fd;
/// Is the file locked?
bool locked;
};
#ifdef SBUILD_FEATURE_DEVLOCK
/**
* Device lock. Set an advisory lock on a device. The lock is
* acquired using liblockdev lock_dev(). Note that a lock_type of
* LOCK_SHARED is equivalent to LOCK_EXCLUSIVE, because this lock
* type does not support shared locks.
*/
class device_lock : public lock
{
public:
/**
* The constructor.
*
* @param device the device to lock (full pathname).
*/
device_lock (std::string const& device);
/// The destructor.
virtual ~device_lock ();
virtual void
set_lock (lock::type lock_type,
unsigned int timeout);
virtual void
unset_lock ();
private:
/// The device to lock.
std::string device;
/// Is the file locked?
bool locked;
};
#endif // SBUILD_FEATURE_DEVLOCK
}
#endif /* SBUILD_LOCK_H */
/*
* Local Variables:
* mode:C++
* End:
*/
|
