Line data    Source code

       1              : /* File locking.
       2              :    Copyright (C) 2023-2026 Free Software Foundation, Inc.
       3              : 
       4              : This file is part of GCC.
       5              : 
       6              : GCC is free software; you can redistribute it and/or modify it under
       7              : the terms of the GNU General Public License as published by the Free
       8              : Software Foundation; either version 3, or (at your option) any later
       9              : version.
      10              : 
      11              : GCC is distributed in the hope that it will be useful, but WITHOUT ANY
      12              : WARRANTY; without even the implied warranty of MERCHANTABILITY or
      13              : FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
      14              : for more details.
      15              : 
      16              : You should have received a copy of the GNU General Public License
      17              : along with GCC; see the file COPYING3.  If not see
      18              : <http://www.gnu.org/licenses/>.  */
      19              : 
      20              : #ifndef LOCKFILE_H
      21              : #define LOCKFILE_H
      22              : 
      23              : /* Used to synchronize across multiple processes.  */
      24         7817 : class lockfile {
      25              : public:
      26              :   /* Default constructor.  */
      27         7817 :   lockfile (): fd (-1)
      28              :   {}
      29              :   /* Intended constructor for use.  Filename should not be used for anything
      30              :      other than locking to prevent unintentional unlock.  */
      31            0 :   lockfile (std::string filename): lockfile ()
      32              :   {
      33            0 :     this->filename = std::move (filename);
      34              :   }
      35              :   lockfile (lockfile const& o): lockfile (o.filename)
      36              :   {}
      37              : 
      38            0 :   void operator=(lockfile o)
      39              :   {
      40            0 :     unlock ();
      41            0 :     this->filename = o.filename;
      42            0 :     this->fd = o.fd;
      43            0 :     o.fd = -1;
      44            0 :   }
      45              : 
      46              :   /* Unique write lock.  No other lock can be held on this lockfile.
      47              :      Blocking call.  */
      48              :   int lock_write ();
      49              : 
      50              :   /* Unique write lock.  No other lock can be held on this lockfile.
      51              :      Only locks if this filelock is not locked by any other process.
      52              :      Return whether locking was successful.  */
      53              :   int try_lock_write ();
      54              : 
      55              :   /* Shared read lock.  Only read lock can be held concurrently.
      56              :      If write lock is already held by this process, it will be
      57              :      changed to read lock.
      58              :      Blocking call.  */
      59              :   int lock_read ();
      60              : 
      61              :   /* Unlock all previously placed locks.  */
      62              :   void unlock ();
      63              : 
      64              :   /* Returns whether any lock is held.  */
      65              :   bool
      66              :   locked ()
      67              :   {
      68              :     return fd < 0;
      69              :   }
      70              : 
      71              :   /* Are lockfiles supported?  */
      72              :   static bool lockfile_supported ();
      73              : private:
      74              :   std::string filename;
      75              :   int fd;
      76              : };
      77              : 
      78              : #endif