selfforum-cgi/shared/Lock/Exclusive.pm

   1 package Lock::Exclusive;
   2
   3 ################################################################################
   4 #                                                                              #
   5 # File:        shared/Lock/Exclusive.pm                                        #
   6 #                                                                              #
   7 # Authors:     André Malo <nd@o3media.de>                                      #
   8 #                                                                              #
   9 # Description: Locking and Filehandle class                                    #
  10 #              using O_EXCL and lock files                                     #
  11 #                                                                              #
  12 ################################################################################
  13
  14 use strict;
  15 use Fcntl;
  16
  17 ################################################################################
  18 #
  19 # Version check
  20 #
  21 # last modified:
  22 #    $Date$ (GMT)
  23 # by $Author$
  24 #
  25 sub VERSION {(q$Revision$ =~ /([\d.]+)\s*$/)[0] or '0.0'}
  26
  27 ### _simple_lock () ############################################################
  28 #
  29 # simple file lock
  30 # (create lock file)
  31 #
  32 # Params: $filename - file to lock
  33 #         $timeout  - timeout
  34 #
  35 # Return: success (boolean)
  36 #
  37 sub _simple_lock {
  38   my ($self, $fh) = @_;
  39
  40   sysopen ($fh, $fh->filename, O_CREAT | O_EXCL | O_WRONLY)
  41     and close $fh
  42     and return 1;
  43
  44   return;
  45 }
  46
  47 ### _simple_unlock () ##########################################################
  48 #
  49 # simple file unlock
  50 # (unlink lock file)
  51 #
  52 # Params: $filename - lockfile name
  53 #                     ^^^^^^^^
  54 #
  55 # Return: success (boolean)
  56 #
  57 sub _simple_unlock {
  58   my ($self, $filename) = @_;
  59
  60   return 1 if (!-f $filename or unlink $filename);
  61
  62   # not able to unlink lock file, hmmm...
  63   #
  64   return;
  65 }
  66
  67 ### _reftime () ################################################################
  68 #
  69 # determine reference time for violent unlock
  70 #
  71 # Params: ~none~
  72 #
  73 # Return: time or zero, if no reference file found
  74 #
  75 sub _reftime {
  76   my $self = shift;
  77   my ($time, $reffile) = 0;
  78
  79   if (-f ($reffile = $self -> filename)) {
  80     $time = (stat $reffile)[9];}
  81
  82   elsif (-f ($reffile = $self -> lockfile)) {
  83     $time = (stat $reffile)[9];}
  84
  85   $time;
  86 }
  87
  88 ### masterlocked () ############################################################
  89 #
  90 # check on master lock status of the file
  91 #
  92 # Params: ~none~
  93 #
  94 # Return: status (boolean)
  95 #
  96 sub masterlocked {-f shift -> masterlock}
  97
  98 ### excl_announced () ##########################################################
  99 #
 100 # check on exclusive lock announced status of the file
 101 #
 102 # Params: ~none~
 103 #
 104 # Return: status (boolean)
 105 #
 106 sub excl_announced {-f shift -> lockfile}
 107
 108 ### exsh_announced () ##########################################################
 109 #
 110 # check on exclusive shared lock status of the file
 111 #
 112 # Params: ~none~
 113 #
 114 # Return: status (boolean)
 115 #
 116 sub exsh_announced {-f shift -> exshlock}
 117
 118 ### purge () ###################################################################
 119 #
 120 # cover our traces after a file was removed
 121 #
 122 # Params: ~none~
 123 #
 124 # Return: ~none~
 125 #
 126 sub purge {
 127   shift -> release;
 128 }
 129
 130 # keep 'require' happy
 131 1;
 132
 133 #
 134 #
 135 ### end of Lock::Exclusive #####################################################