Detect empty xml element tag - perl

Question

I have to parse an xml document , decode base64 values from specific elements and printout those fields and the corresponding decoded values. Some of the elements don't have value I want to print the name of the element and "no value" string or simply \n, but somehow I cannot match empty string '' or undefined value.
Example input file:
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<?xml-stylesheet href="ums_v1.xsl" type="text/xsl"?>
<ums>
<datatype>Report</datatype>
<reference><![CDATA[NDkxNzYwNDAyNjMwODAy]]></reference>
<sequence></sequence>
<calling-party><![CDATA[NDkxNzYwNDAyNjMwOA==]]></calling-party>
<IP></IP>
<called-party><![CDATA[NDk4OTI0NDI0Mzc0]]></called-party>
<start>26/02/14 09:28:55</start>
<settings></settings>
<direction><![CDATA[Z2VzZW5kZXQ=]]></direction>
<result><![CDATA[ZXJmb2xncmVpY2g=]]></result>
<fax-tif></fax-tif>
<fax-jpg></fax-jpg>
<fax-png></fax-png>
<audio-wav></audio-wav>
<audio-mp3></audio-mp3>
<sms></sms>
<mms></mms>
</ums>
My program:
#!/usr/bin/perl -w
use XML::Parser;
use MIME::Base64;
use feature qw/switch/;
my $message; # Hashref containing infos on a message
while ($file = shift(#ARGV)) {
print "========================================================\n";
print "file: $file \n";
print "========================================================\n";
my $parser = new XML::Parser ( Handlers => { # Creates parser object
Start => \&hdl_start,
End => \&hdl_end,
Char => \&hdl_char,
});
$parser->parsefile($file);
print "========================================================\n";
}
sub hdl_start{
my ($p, $elt, %atts) = #_;
$atts{'_str'} = '';
given ($elt) {
when ((/^reference/) || (/^sequence/) || (/^calling-party/) || (/^called-party/) || (/^settings/) || (/^direction/) || (/^sms/) || (/^result/)) {
$message = \%atts;
}
when (/^audio-mp3/) {
$message = \%atts;
}
when (/^audio-mp3/) {
$message = \%atts;
}
when (/^mms/) {
$message = \%atts;
}
}
}
sub hdl_end{
my ($p, $elt) = #_;
given ($elt) {
when ((/^reference/) || (/^sequence/) || (/^calling-party/) || (/^called-party/) || (/^settings/) || (/^direction/) || (/^sms/) || (/^result/)) {
print "$elt : " ;
format_message($message) if $message && $message->{'_str'} =~ /\S/;
}
when (/^audio-mp3/) {
print "audio content in $file\.mp3\n" ;
format_mp3($message) if $message && $message->{'_str'} =~ /\S/;
}
when (/^audio-wav/) {
print "audio content in $file\.wav\n" ;
format_wav($message) if $message && $message->{'_str'} =~ /\S/;
# print "$Audiowav->{'_str'}";
}
when (/^mms/) {
print "mms content in $file\.mms, depending on the mms content further processing may be needed\n" ;
format_mms($message) if $message && $message->{'_str'} =~ /\S/;
}
}
}
sub hdl_char {
my ($p, $str) = #_;
$message->{'_str'} .=$str;
}
sub hdl_def { } # We just throw everything else
sub format_message { # Helper sub to nicely format what we got from the XML and decode base64 values of the needed attributes
my $atts = shift;
$atts->{'_str'} =~ s/\n//g;
if (!defined($atts->{'_str'})) { print "\n"}
my $decoded = decode_base64($atts->{'_str'});
print " $decoded\n";
# if (!$decoded) {print "\n"}
undef $message;
}
sub format_mp3 { # decode base64 content and save to mp3 file - for the audio-mp3 tag
my $atts = shift;
open FILE, "> ./$file.mp3" or die $!;
$atts->{'_str'} =~ s/\n//g;
# print "mp3: $atts $atts->{'_str'}\n";
my $decoded = decode_base64($atts->{'_str'});
print FILE $decoded;
close FILE;
undef $message;
}
sub format_wav { # decode base64 content and save to wav file - for the audio-wav tag
my $atts = shift;
open FILE, "> ./$file.wav" or die $!;
$atts->{'_str'} =~ s/\n//g;
print "wav: $atts $atts->{'_str'}\n";
my $decoded = decode_base64($atts->{'_str'});
print "$decoded\n";
print FILE $decoded;
close FILE;
undef $message;
}
sub format_mms { # decode mms base64 content and save to file - depending on the content further processing may be needed
my $atts = shift;
open FILE, "> ./$file.wav" or die $!;
$atts->{'_str'} =~ s/\n//g;
print "wav: $atts $atts->{'_str'}\n";
my $decoded = decode_base64($atts->{'_str'});
print "$decoded\n";
print FILE $decoded;
close FILE;
undef $message;
}
I've tried in format_message subroutine different matches, I've tried also in the hdl_end - any idea?
thanks in advance

Answer 1

Using XML::LibXML:
use strict;
use warnings;
use XML::LibXML;
my $string = do { local $/; <DATA> };
my $dom = XML::LibXML->load_xml(string => $string);
for my $node ($dom->findnodes(q{//*})) {
if ($node->textContent() eq '') {
print $node->nodeName, "\n";
}
}
__DATA__
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<?xml-stylesheet href="ums_v1.xsl" type="text/xsl"?>
<ums>
<datatype>Report</datatype>
<reference><![CDATA[NDkxNzYwNDAyNjMwODAy]]></reference>
<sequence></sequence>
<calling-party><![CDATA[NDkxNzYwNDAyNjMwOA==]]></calling-party>
<IP></IP>
<called-party><![CDATA[NDk4OTI0NDI0Mzc0]]></called-party>
<start>26/02/14 09:28:55</start>
<settings></settings>
<direction><![CDATA[Z2VzZW5kZXQ=]]></direction>
<result><![CDATA[ZXJmb2xncmVpY2g=]]></result>
<fax-tif></fax-tif>
<fax-jpg></fax-jpg>
<fax-png></fax-png>
<audio-wav></audio-wav>
<audio-mp3></audio-mp3>
<sms></sms>
<mms></mms>
</ums>
Outputs:
sequence
IP
settings
fax-tif
fax-jpg
fax-png
audio-wav
audio-mp3
sms
mms

Answer 2

Solution is to test the empty tag in the end handler, like:
sub hdl_end{
my ($p, $elt) = #_;
given ($elt) {
when ((/^reference/) || (/^sequence/) || (/^calling-party/) || (/^called-party/) || (/^settings/) || (/^direction/) || (/^sms/) || (/^result/)) {
print "$elt : " ;
format_message($message) if $message && $message->{'_str'} =~ /\S/;
print "no value\n" if $message && $message->{'_str'} !~ /\S/;
}
when (/^audio-mp3/) {
print "audio content in $file\.mp3\n" if $message && $message->{'_str'} =~ /\S/;
format_mp3($message) if $message && $message->{'_str'} =~ /\S/;
}
when (/^audio-wav/) {
print "audio content in $file\.wav\n" if $message && $message->{'_str'} =~ /\S/ ;
format_wav($message) if $message && $message->{'_str'} =~ /\S/;
}
when (/^mms/) {
print "mms content in $file\.mms, depending on the mms content further processing may be needed\n" if $message && $message->{'_str'} =~ /\S/;
format_mms($message) if $message && $message->{'_str'} =~ /\S/;
}
}
}
So the if $message->{'_str'} !~ /\S/ is what I needed ... Thank you all for the effort!