file Utils/file_lock.hpp #

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Detailed Description #

Author: Ben Farmer (ben.farmer@gmail.com)

Date: 2016 Feb

GAMBIT file locking functions Use these to block access to sensitive parts of the code by other processes when we are using them. For example, some backends do stupid things like initialise themselves by writing and reading files; use these routines to force only one process at a time to perform these routines.

Usage:

{ Utils::FileLock mylock(“some_unique_name”); mylock.get_lock(); /* Do sensitive stuff. No other process will be allowed into this code region while we are here. / mylock.release_lock(); } / If not already done, lock is automatically released when ‘mylock’ is destructed */

Authors (add name and date if you modify):

Source code #

//   GAMBIT: Global and Modular BSM Inference Tool
//   *********************************************
///  \file
///
///  GAMBIT file locking functions
///  Use these to block access to sensitive parts
///  of the code by other processes when we are
///  using them. For example, some backends
///  do stupid things like initialise themselves
///  by writing and reading files; use these
///  routines to force only one process at a time
///  to perform these routines.
///
///  Usage:
///
///   {
///     Utils::FileLock mylock("some_unique_name");
///     mylock.get_lock();
///     /* Do sensitive stuff. No other process will
///        be allowed into this code region while we
///        are here. */
///     mylock.release_lock();
///   }
///   /* If not already done, lock is automatically
///      released when 'mylock' is destructed */
///
///  *********************************************
///
///  Authors (add name and date if you modify):
///
///  \author Ben Farmer
///          (ben.farmer@gmail.com)
///  \date 2016 Feb
///
///  *********************************************

#ifndef __file_lock_hpp__
#define __file_lock_hpp__

#include <string>

namespace Gambit
{
   namespace Utils
   {

      /// Class to manage a file lock
      /// Lock will be automatically released if this object is destructed
      class FileLock
      {
        private:

          /// Name for the managed lock file
          const std::string my_lock_fname;

          /// C file descriptor for the lock file
          const int fd;

          /// Bool to indicate if we already have the lock
          bool have_lock;

          /// Bool to indicate that hard errors should be thrown rather than gambit errors (e.g. for use in loggers)
          bool hard_errors;

          /// Bool to indicate if the file has the ability to be exhaustible
          bool exhaustible;

          /// Bool to indicate whether the lock has been exhausted or not
          bool exhausted_lock;

        public:
          /// Constructor
          FileLock(const std::string& fname, const bool is_exhaustible=false, const bool harderrs=false);

          /// Destructor
          /// Closing the file descriptor will automatically release any lock we might have
          ~FileLock();

          /// Obtain lock (or wait if lock cannot be obtained, and then obtain lock)
          void get_lock();

          /// Release a lock (error if no lock held)
          void release_lock();

          /// Getter for lockfile name
          const std::string& get_filename() const;

          /// Check if lock is exhausted
          bool exhausted();
      };


      /// Class to manage a process lock, using a file
      class ProcessLock : public FileLock
      {
        private:
          /// Static variable for the lock-file prefix path, i.e. where to store the lock file
          static const std::string lock_prefix;

          /// Static variable for the lock-file extension
          static const std::string lock_suffix;

        public:
          /// Constructor
          ProcessLock(const std::string& fname, const bool is_exhaustible=true, const bool harderrs=false);

          /// Clean up existing process locks
          static void clean_locks();
      };

   }
}

#endif

Updated on 2024-07-18 at 13:53:32 +0000