mdw@git.distorted.org.uk Git - mLib/blob - lock.h

   1 /* -*-c-*-
   2  *
   3  * $Id: lock.h,v 1.3 2004/04/08 01:36:13 mdw Exp $
   4  *
   5  * Simplified POSIX locking interface
   6  *
   7  * (c) 1999 Straylight/Edgeware
   8  */
   9
  10 /*----- Licensing notice --------------------------------------------------*
  11  *
  12  * This file is part of the mLib utilities library.
  13  *
  14  * mLib is free software; you can redistribute it and/or modify
  15  * it under the terms of the GNU Library General Public License as
  16  * published by the Free Software Foundation; either version 2 of the
  17  * License, or (at your option) any later version.
  18  *
  19  * mLib is distributed in the hope that it will be useful,
  20  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22  * GNU Library General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU Library General Public
  25  * License along with mLib; if not, write to the Free
  26  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  27  * MA 02111-1307, USA.
  28  */
  29
  30 #ifndef MLIB_LOCK_H
  31 #define MLIB_LOCK_H
  32
  33 #ifdef __cplusplus
  34   extern "C" {
  35 #endif
  36
  37 /*----- Magic constants ---------------------------------------------------*/
  38
  39 enum {
  40   LOCK_UNLOCK,                          /* Release a lock I obtained */
  41   LOCK_EXCL,                            /* Obtain an exclusive lock */
  42   LOCK_NONEXCL                          /* Obtain a nonexclusive lock */
  43 };
  44
  45 /*----- Functions provided ------------------------------------------------*/
  46
  47 /* --- @lock_file@ --- *
  48  *
  49  * Arguments:   @int fd@ = file descriptor to lock
  50  *              @unsigned how@ = type of lock required
  51  *
  52  * Returns:     0 if OK, -1 if it failed.
  53  *
  54  * Use:         Acquires a lock on the given file.  The value @how@
  55  *              specifies the type of lock to acquire: @LOCK_EXCL@ gets
  56  *              an exclusive (write) lock; @LOCK_NONEXCL@ gets a non-
  57  *              exclusive (read) lock and @LOCK_UNLOCK@ releases any locks.
  58  *              Acquiring a lock gets timed out after a while with an
  59  *              error.
  60  */
  61
  62 extern int lock_file(int /*fd*/, unsigned /*how*/);
  63
  64 /*----- That's all, folks -------------------------------------------------*/
  65
  66 #ifdef __cplusplus
  67   }
  68 #endif
  69
  70 #endif