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String Correction and Non-Printable Characters Using XML :: Twig in Win32 Perl

This is a really weird problem. It took me almost all day to destroy it to a small executable script file that fully demonstrates the problem.

Summary of the problem: I use XML :: Twig to pull a piece of data from an XML file, then I stick to this piece of data in the middle of another piece of data, let me call it the parent data. Parent data has this weird non-printable character at the beginning when I start. The provider provided the data, so I can’t control it. My problem is that after I insert a piece of data in the middle of the parent data, the final product has its new non-printable character from the very beginning, in addition to the one it started from the beginning. This new non-printable character contained neither parent data nor a detailed piece of data. I do not know where it came from, or how it gets into my data.

I doubt this is an XML :: Twig error, because line damage occurs while reading a line from a file descriptor in a while loop, but I was unsuccessful at recreating my problem when deleting XML :: Twig in my scripts, so I had to leave it .

This is my first experience with non-printable characters in strings that I am trying to process. Do I need to do something special instead of treating them like regular strings or something else?

I am using ActiveState Perl 5.10.1 and XML :: Twig 3.32 (latest version) and the Eclipse 3.5.1 IDE on Windows XP.

Here is a script that demonstrates the problem:

use strict; 
use warnings; 
use XML::Twig; 

my $FALSE = 0;
my $TRUE = 1;
my $name = 'KurtsProgram';
my $task = 'MainTask';
my $hidden_char = "\xBF";
my $data = $hidden_char . 
'(*********************************************
  Data-File-Header-Junk
**********************************************)

    PROGRAM MainProgram ()
    END_PROGRAM

    TASK SecondaryTask ()
    END_TASK

    TASK MainTask ()
        MainProgram;
    END_TASK
';
my $new_data = insertProgram( $name, $task, $data );

# test to see if results start out as expected
if ( $new_data =~ m/^\Q$hidden_char\E/ ) {
    print "SUCCESS\n";
}
else {
    print STDERR "ERROR: What happened?\n";
    print STDERR "ORIGINAL: \n$data\n";
    print STDERR "MODIFIED: \n$new_data\n";
}

sub insertProgram {
    my ( $local_name, $local_task, $local_data ) = @_;

    # get program section from XML template
    my $twig = new XML::Twig;
    $twig->parse( '<?xml version="1.0"?>
<TemplateSet>
    <PROGRAM>PROGRAM <Name>ProgramNameGoesHere</Name> ()
    END_PROGRAM</PROGRAM>
    <TASK>TASK <Name>TaskNameGoesHere</Name> ()
    END_TASK</TASK>
</TemplateSet>
' );   
    my $program = $twig->root->first_child('PROGRAM');

    # replace program name in XML template
    $program->first_child('Name')->set_text($local_name);
    my $insert = $program->text();

    # stick modified program into data
    if ( $local_data =~ s/(\s+PROGRAM\s+[^\s]+\s+\()/\n\n    $insert $1/ ) {
        # found it and inserted new program
    }
    else {
        # not found
        return;
    }

    # add program name to task list
    my $added_program_to_task = $FALSE;
    my $found_start = $FALSE;
    my $found_end = $FALSE;
    my $new_data = "";
    # open string as a filehandle for line by line processing
    my $filehandle;
    open( $filehandle, '<', \$local_data )
        or die("Can't open string as a filehandle: $!");
    while (defined (my $line = <$filehandle>)) {
        # look for start of our task
        if ( 
               ( !$found_start ) &&
               ( $line =~ m/\s+TASK\s+\Q$local_task\E\s+\(/ )
            ) {
            # found the task!
            $found_start = $TRUE;
        }

        # look for end of our task
        if (
                ( $found_start ) && ( !$found_end ) &&
                ( $line =~ m/\s+END_TASK/ )
            )
        {
            # found the end tag for the task section!
            $found_end = $TRUE;

            # add the program name to the bottom of the list
            $line = "        " . $local_name . ";\n" . $line;
            $added_program_to_task = $TRUE;
        }

        # compile new data from processed line or original line
        $new_data = $new_data . $line;
    }
    close($filehandle);

    if ($added_program_to_task) {
        # success
    }
    else {
        # unable to find task
        return;
    }

    return $new_data;
}

When I run this script, I get the following output:

ERROR: What happened?
ORIGINAL: 
¿(*********************************************
      Data-File-Header-Junk
    **********************************************)

        PROGRAM MainProgram ()
        END_PROGRAM

        TASK SecondaryTask ()
        END_TASK

        TASK MainTask ()
            MainProgram;
        END_TASK

MODIFIED: 
¿(*********************************************
      Data-File-Header-Junk
    **********************************************)

        PROGRAM KurtsProgram ()
        END_PROGRAM 

        PROGRAM MainProgram ()
        END_PROGRAM

        TASK SecondaryTask ()
        END_TASK

        TASK MainTask ()
            MainProgram;
            KurtsProgram;
        END_TASK

You can see the extra character that has been added to the data front right below M in MODIFIED.

+5
2

ISO-8859-1 UTF-8 : \xBF → \xC2\xBF.

XML:: Twig UTF-8 (. ).

, Twig , keep_encoding ( . FAQ XML:: Twig: XML-/ , grok Unicode, XML:: Twig ?).

, , UTF-8 , , , , .

+7

, , , , , (. Unicode), XML, ? - xBF, UTF-8.

+1

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