comment on

Alright, in my Perl codings, I've done some work with respect to Wikipedia. One thing you'll find on Wikipedia is plenty of Unicode. Now unfortunately, I've come across some snags when trying to do some work. Since I'm not conversant with all the Black Magic(tm) with Character Encodings when I mention Unicode, I likely mean the UTF8 encoding of it.

Lets establish some facts:

Titles can be Unicode strings
Example title is: Rīga-Herson-Astrahan
This (should) escaped to: R%C4%ABga-Herson-Astrahan
When (not) marked as UTF8, it decodes correctly
When marked as UTF8, it decodes incorrectly

Stepping through the code I have provided below, you eventually to URI at line 77:

  DB<18> x $str
0  'http://en.wikipedia.org/w/api.php?prop=revisions&format=xml&titles
+=User:OverlordQ/R&#299;ga-Herson-Astrahan&action=query&rvlimit=20'
[download]

The first run through the regex, it eats a character:

  DB<20> p $1
▒
  DB<21> x unpack("U*",$1);
0  196

Odd, oh well, let us let the regex finish until we get to line 78. Now lets see what the url contains:

  DB<24> x $str
0  'http://en.wikipedia.org/w/api.php?prop=revisions&format=xml&titles
+=User:OverlordQ/R%C3%84%C2%ABga-Herson-Astrahan&action=query&rvlimit=
+20'
[download]

Hurm, not fun, that's not what we should have got. Bug? Or should I not be telling perl that these strings may contain utf8 characters. Example below. (It abuses the pre tag since the code tag eats the characters)

#!/usr/bin/perl
use strict;
use warnings;
use lib '/home/overlordq/lib';
use LWP::UserAgent;
use Data::Dumper;
use DBI;
use wikidb;

$|++;

my $ua = LWP::UserAgent->new();

my $dbh = DBI->connect("DBI:mysql:database=enwiki_p;host=sql-s1",$user
+,$password);
my $query = "SELECT page_title FROM page WHERE page_title LIKE 'Overlo
+rdQ%' AND page_id = '22325873'";
my $sth = $dbh->prepare($query);
$sth->execute();
my $title;
while(my $ref = $sth->fetchrow_hashref() ) {
        $title = $ref->{'page_title'};
}

print "Title: $title\n";
if( isUTF($title) ) {
        print "\tis UTF8\n";
} else {
        print "\tis not UTF8\n";
}

my $res = $ua->post('http://en.wikipedia.org/w/api.php?prop=revisions&
+format=xml&titles=User:' . $title . '&action=query&rvlimit=20');

my $uriUsed = $res->request->uri->as_string;

print "URI: $uriUsed\n";

if( isUTF($title) ) {
        print "\tis already UTF8\n";
} else {
        utf8::upgrade($title);
        if( isUTF($title) ) {

                print "$title\n\tis now UTF8\n";
        }
}

$res = $ua->post('http://en.wikipedia.org/w/api.php?prop=revisions&for
+mat=xml&titles=User:' . $title . '&action=query&rvlimit=20');

$uriUsed = $res->request->uri->as_string;

print "URI: $uriUsed\n";


print "Title: $title\n";

sub isUTF {
        my $string = shift;
        return utf8::is_utf8($string);
}
[download]

Output:

Title: OverlordQ/Rīga-Herson-Astrahan
        is not UTF8
URI: ... User:OverlordQ/R%C4%ABga-Herson-Astrahan&action=query&rvlimit=20
OverlordQ/Rīga-Herson-Astrahan
        is now UTF8
URI: ... User:OverlordQ/R%C3%84%C2%ABga-Herson-Astrahan&action=query&rvlimit=20
Title: OverlordQ/Rīga-Herson-Astrahan

Now for my revised node:

Update: Since it looks like reapage is out of the picture, I'll put back what I can reccollect from memory. Yes it (ab)uses pre since code eats the characters.

Now why is this thar LWP mangling my UTF8 strings? Here is mah source:

#!/usr/bin/perl
use strict;
use warnings;
use lib '/home/overlordq/lib';
use LWP::UserAgent;
use Data::Dumper;
use DBI;
use wikidb;

$|++;

my $ua = LWP::UserAgent->new();

my $dbh = DBI->connect("DBI:mysql:database=enwiki_p;host=sql-s1",$user
+,$password);
my $query = <<SQL;
SELECT
        p1.page_namespace AS namespace,
        p1.page_title AS title,
        rd_namespace,
        rd_title FROM redirect AS rd
JOIN
        page p1 ON
                (rd.rd_from=p1.page_id)
LEFT JOIN
        page AS p2 ON
                (rd_namespace=p2.page_namespace AND rd_title=p2.page_t
+itle)
WHERE
        rd_namespace >= 0
AND
        p2.page_namespace IS NULL
AND
        p1.page_title LIKE 'OverlordQ%'
SQL

my $sth = $dbh->prepare($query);
$sth->execute();
my $title;
while(my $ref = $sth->fetchrow_hashref() ) {
        $title = $ref->{'title'};

print "$title\n";

my $prefix = 'http://en.wikipedia.org/w/api.php?prop=revisions&format=
+json&titles=User:';
my $postfix = '&action=query&rvlimit=20';

if( isUTF($title) ) {
        print "\tis UTF8\n";
} else {
        print "\tis not UTF8\n";
}

my $res = $ua->get($prefix.$title.$postfix);

my $url = $res->request->uri->as_string;

print "URI: $url\n";

if( isUTF($title) ) {
        print "\tis already UTF8\n";
} else {
        utf8::upgrade($title);
        if( isUTF($title) ) {
                print "$title\n\tis now UTF8\n";
        }
}


$res = $ua->get($prefix.$title.$postfix);

$url = $res->request->uri->as_string;
print "URI: $url\n";

}

sub isUTF {
        my $string = shift;
        return utf8::is_utf8($string);
}
[download]

Output is:

OverlordQ/Rīga-Herson-Astrahan
        is not UTF8
URI: ... /R%C4%ABga-Herson-Astrahan&action=query&rvlimit=20
OverlordQ/Rīga-Herson-Astrahan
        is now UTF8
URI: ... /R%C3%84%C2%ABga-Herson-Astrahan&action=query&rvlimit=20

Of course what I should have done, had I not skimmed the Encode and perlunitut pages was I should have added:

binmode STDOUT, ':utf8';
[download]

Doesn't help that although my terminal handles utf8 that perl wont give it to me. So lets try add that at the top and see what we get:

OverlordQ/Rīga-Herson-Astrahan
        is not UTF8
URI: ... /R%C4%ABga-Herson-Astrahan&action=query&rvlimit=20
OverlordQ/Rīga-Herson-Astrahan
        is now UTF8
URI: ... /R%C3%84%C2%ABga-Herson-Astrahan&action=query&rvlimit=20

Ah hah, now we see why it's encoding to %C3%84%C2%AB instead of %C4%AB. Yay for character encoding, so lets finally throw in a

$title = decode('utf8',$title);
[download]

Underneath where it gets the title.

OverlordQ/Rīga-Herson-Astrahan
        is UTF8
URI: ... /R%C4%ABga-Herson-Astrahan&action=query&rvlimit=20
        is already UTF8
URI: ... /R%C4%ABga-Herson-Astrahan&action=query&rvlimit=20

So remember kids, flipping the flag without converting is bad, mkay.

Revised source:

#!/usr/bin/perl
use strict;
use warnings;
use lib '/home/overlordq/lib';
use LWP::UserAgent;
use Data::Dumper;
use DBI;
use Encode;
use wikidb;

$|++;
binmode STDOUT, ":utf8";

my $ua = LWP::UserAgent->new();

my $dbh = DBI->connect("DBI:mysql:database=enwiki_p;host=sql-s1",$user
+,$password);
my $query = <<SQL;
SELECT
        p1.page_namespace AS namespace,
        p1.page_title AS title,
        rd_namespace,
        rd_title FROM redirect AS rd
JOIN
        page p1 ON
                (rd.rd_from=p1.page_id)
LEFT JOIN
        page AS p2 ON
                (rd_namespace=p2.page_namespace AND rd_title=p2.page_t
+itle)
WHERE
        rd_namespace >= 0
AND
        p2.page_namespace IS NULL
AND
        p1.page_title LIKE 'OverlordQ%'
SQL

my $sth = $dbh->prepare($query);
$sth->execute();
my $title;
while(my $ref = $sth->fetchrow_hashref() ) {
        $title = $ref->{'title'};

$title = decode('utf8',$title);

print "$title\n";

my $prefix = 'http://en.wikipedia.org/w/api.php?prop=revisions&format=
+json&titles=User:';
my $postfix = '&action=query&rvlimit=20';

if( isUTF($title) ) {
        print "\tis UTF8\n";
} else {
        print "\tis not UTF8\n";
}

my $res = $ua->get($prefix.$title.$postfix);

my $url = $res->request->uri->as_string;

print "URI: $url\n";

if( isUTF($title) ) {
        print "\tis already UTF8\n";
} else {
        utf8::upgrade($title);
        if( isUTF($title) ) {
                print "$title\n\tis now UTF8\n";
        }
}


$res = $ua->get($prefix.$title.$postfix);

$url = $res->request->uri->as_string;
print "URI: $url\n";

}

sub isUTF {
        my $string = shift;
        return utf8::is_utf8($string);
}
[download]

In reply to URIs and UTF8 by OverlordQ

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		`&`
	<		`<`
	>		`>`
	[		`[`
	]		`]`

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.