selfforum-cgi/shared/Lock/Symlink.pm

   1 package Lock::Symlink;
   2
   3 ################################################################################
   4 #                                                                              #
   5 # File:        shared/Lock/Symlink.pm                                          #
   6 #                                                                              #
   7 # Authors:     André Malo <nd@o3media.de>                                      #
   8 #                                                                              #
   9 # Description: Locking and Filehandle class                                    #
  10 #              using symlinks                                                  #
  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   symlink $self->filename, $fh->filename and return 1;
  41
  42   return;
  43 }
  44
  45 ### _simple_unlock () ##########################################################
  46 #
  47 # simple file unlock
  48 # (unlink lock file)
  49 #
  50 # Params: $filename - lockfile name
  51 #                     ^^^^^^^^
  52 #
  53 # Return: success (boolean)
  54 #
  55 sub _simple_unlock {
  56   my ($self, $filename) = @_;
  57
  58   return 1 if (!-l $filename or unlink $filename);
  59
  60   # not able to unlink symlink, hmmm...
  61   #
  62   return;
  63 }
  64
  65 ### _reftime () ################################################################
  66 #
  67 # determine reference time for violent unlock
  68 #
  69 # Params: ~none~
  70 #
  71 # Return: time or zero, if no reference file found
  72 #
  73 sub _reftime {
  74   my $self = shift;
  75   my ($time, $reffile) = 0;
  76
  77   if (-f ($reffile = $self -> filename)) {
  78     $time = (stat $reffile)[9];}
  79
  80   elsif (-l ($reffile = $self -> lockfile)) {
  81     $time = (lstat $reffile)[9];}
  82
  83   $time;
  84 }
  85
  86 ### masterlocked () ############################################################
  87 #
  88 # check on master lock status of the file
  89 #
  90 # Params: ~none~
  91 #
  92 # Return: status (boolean)
  93 #
  94 sub masterlocked {-l shift -> masterlock}
  95
  96 ### excl_announced () ##########################################################
  97 #
  98 # check on exclusive lock announced status of the file
  99 #
 100 # Params: ~none~
 101 #
 102 # Return: status (boolean)
 103 #
 104 sub excl_announced {-l shift -> lockfile}
 105
 106 ### exsh_announced () ##########################################################
 107 #
 108 # check on exclusive shared lock status of the file
 109 #
 110 # Params: ~none~
 111 #
 112 # Return: status (boolean)
 113 #
 114 sub exsh_announced {-l shift -> exshlock}
 115
 116 ### purge () ###################################################################
 117 #
 118 # cover our traces after a file was removed
 119 #
 120 # Params: ~none~
 121 #
 122 # Return: ~none~
 123 #
 124 sub purge {
 125   shift -> release;
 126 }
 127
 128 # keep 'require' happy
 129 1;
 130
 131 #
 132 #
 133 ### end of Lock::Symlink #######################################################