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#!/usr/bin/perl
#
# Copyright (C) 1996-2010, OFFIS e.V.
# All rights reserved. See COPYRIGHT file for details.
#
# This software and supporting documentation were developed by
#
# OFFIS e.V.
# R&D Division Health
# Escherweg 2
# D-26121 Oldenburg, Germany
#
# for CEN/TC251/WG4 as a contribution to the Computer Assisted Radiology
# (CAR) 1996 DICOM Demonstration.
#
#
# Module: dcmwlm (WWW Component)
#
# Author: Marco Eichelberg
#
# Purpose:
# This module contains perl procedures which allow to set/unset
# read and write locks on one certain file (which is stored in a
# global variable).
# The procedures use the perl fcntl() call instead of flock() in order
# to be "compatible" with the dcmtk Basic Worklist Management components
# written in C++, on both BSD and System V platforms.
# Since the "struct flock" required for fcntl() is defined differently
# on every system, this perl script relies on a C program "preplock" which
# initialises the flock structure from <fcntl.h> and passes the result
# to perl.
#
# Last Update: $Author: joergr $
# Update Date: $Date: 2010-10-14 13:02:01 $
# CVS/RCS Revision: $Revision: 1.2 $
# Status: $State: Exp $
#
# CVS/RCS Log
# $Log: lock.ph,v $
# Revision 1.2 2010-10-14 13:02:01 joergr
# Updated copyright header. Added reference to COPYRIGHT file.
#
# Revision 1.1 2002/12/03 12:16:06 wilkens
# Added files und functionality from the dcmtk/wlisctn folder to dcmtk/dcmwlm
# so that dcmwlm can now completely replace wlistctn in the public domain part
# of dcmtk. Pertaining to this replacement requirement, another optional return
# key attribute was integrated into the wlm utilities.
#
#
#
require 'prefs.ph';
$fcntldata=`$prefs{'preplock'}`;
eval $fcntldata;
$fd_inuse=0; # 0=no_lock, 1=read_lock, 2=write_lock
#
# usage: &set_readlock('pathname');
# returns 1 if successful, 0 upon failure.
# modifies the global variable $fd_inuse and the file descriptor fd.
#
sub set_readlock
{
local($lockname, $last, $fcntldata);
if ((@_ != 1)||($_[0] eq ''))
{
printf(stderr "error: NULL path not allowed\n");
return 0;
}
$lockname = $_[0];
if ($fd_inuse ne 0)
{
printf(stderr "error: nested read locks not allowed!\n");
return 0;
}
$last = chop($lockname);
if ($last eq '/')
{
$lockname = join('','+<',$lockname,$last,$prefs{'lockfile'});
} else {
$lockname = join('','+<',$lockname,$last,'/',$prefs{'lockfile'});
}
if (!open(fd, $lockname))
{
$fd_inuse = 0;
printf(stderr "error: cannot open file %s\n",$lockname);
return 0;
} else {
$fd_inuse=1;
}
$fcntldata = $const_RDLCK_STRUCT;
if (-1 eq fcntl(fd,$const_F_SETLKW, $fcntldata))
{
printf(stderr "error: cannot set read lock on file %s\n",$lockname);
close(fd);
$fd_inuse = 0;
return 0;
}
return 1;
}
#
# usage: &set_writelock('pathname');
# returns 1 if successful, 0 upon failure.
# modifies the global variable $fd_inuse and the file descriptor fd.
#
sub set_writelock
{
local($lockname, $last, $fcntldata);
if ((@_ != 1)||($_[0] eq ''))
{
printf(stderr "error: NULL path not allowed\n");
return 0;
}
$lockname = $_[0];
if ($fd_inuse eq 2)
{
printf(stderr "error: nested write locks not allowed!\n");
return 0;
}
$last = chop($lockname);
if ($last eq '/')
{
$lockname = join('','+<',$lockname,$last,$prefs{'lockfile'});
} else {
$lockname = join('','+<',$lockname,$last,'/',$prefs{'lockfile'});
}
if ($fd_inuse eq 0)
{
if (!open(fd, $lockname))
{
$fd_inuse = 0;
printf(stderr "error: cannot open file %s\n",$lockname);
return 0;
}
}
$fcntldata = $const_WRLCK_STRUCT;
if (-1 eq fcntl(fd,$const_F_SETLKW, $fcntldata))
{
printf(stderr "error: cannot set write lock on file %s\n",$lockname);
close(fd);
$fd_inuse = 0;
return 0;
}
$fd_inuse=2;
return 1;
}
#
# usage: &release_lock;
# returns 1 if successful, 0 upon failure.
# modifies the global variable $fd_inuse and the file descriptor fd.
#
sub release_lock
{
local($lockname, $last, $fcntldata);
if ($fd_inuse eq 0)
{
printf(stderr "error: no lock to release!\n");
return 0;
}
$fcntldata = $const_UNLCK_STRUCT;
if (-1 eq fcntl(fd,$const_F_SETLKW, $fcntldata))
{
printf(stderr "error: cannot release lock.\n");
close(fd);
$fd_inuse = 0;
return 0;
}
$fd_inuse = 0;
return 1;
}
1;
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