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Re^3: Is there some universal Unicode+UTF8 switch?

by daxim (Curate)
on Sep 02, 2019 at 11:02 UTC ( #11105426=note: print w/replies, xml ) Need Help??


in reply to Re^2: Is there some universal Unicode+UTF8 switch?
in thread Is there some universal Unicode+UTF8 switch?

Your understanding of the topic is still inadequate. I am convinced that you already know "enough to be dangerous", but not enough to arrive at the correctly modelled solution that most other Perl programmers would implement. It's quite difficult to suss out the parts where you still need education or clearing up a misunderstanding, but I will try anyway.

One half of what the utf8 pragma does, is allowing to use non-ASCII character literals in the source code, for example you could simply write

use utf8; my $aufrom = "Барсучелло";
instead of the much more tedious
my $aufrom = "\N{CYRILLIC CAPITAL LETTER BE}\N{CYRILLIC SMALL LETTER A}\N{CYRILLIC SMALL LETTER ER}\N{CYRILLIC SMALL LETTER ES}\N{CYRILLIC SMALL LETTER U}\N{CYRILLIC SMALL LETTER CHE}\N{CYRILLIC SMALL LETTER IE}\N{CYRILLIC SMALL LETTER EL}\N{CYRILLIC SMALL LETTER EL}\N{CYRILLIC SMALL LETTER O}";
or unreadable
my $aufrom = "\N{U+0411}\N{U+0430}\N{U+0440}\N{U+0441}\N{U+0443}\N{U+0447}\N{U+0435}\N{U+043B}\N{U+043B}\N{U+043E}";

The other half of the utf8 pragma is that Perl expects the source code to be encoded in UTF-8. To be clear, that's the encoding option in the text editor. A hex dump of the file with the first example from above would correctly look like:

00000000  75 73 65 20 75 74 66 38  3b 20 6d 79 20 24 61 75 use utf8; my $au
00000010  66 72 6f 6d 20 3d 20 22  d0 91 d0 b0 d1 80 d1 81 from = "��
00000020  d1 83 d1 87 d0 b5 d0 bb  d0 bb d0 be 22 3b 0a    ��елло";␊
If you would mistakenly save the text as Windows-1251, the program would not work correctly anymore.
00000000  75 73 65 20 75 74 66 38  3b 20 6d 79 20 24 61 75 use utf8; my $au
00000010  66 72 6f 6d 20 3d 20 22  c1 e0 f0 f1 f3 f7 e5 eb from = "
00000020  eb ee 22 3b 0a                                   ";␊
# Malformed UTF-8 character: \xc1\xe0 (unexpected non-continuation byte 0xe0, immediately after start byte 0xc1; need 2 bytes, got 1) at 

Therefore the name utf8 for the pragma really is appropriate, and unicode is not.


> > what encoding is it in?
> It is in Unicode.
Unicode is not a valid encoding name for a JSON file or JSON HTTP response body. Again, if you look at the hex dump for both formatversion=1 and formatversion=2, you will see that both are octets encoded in UTF-8.
# formatversion=2
00000000  7b 22 62 61 74 63 68 63  6f 6d 70 6c 65 74 65 22 {"batchcomplete"
00000010  3a 74 72 75 65 2c 22 63  6f 6e 74 69 6e 75 65 22 :true,"continue"
00000020  3a 7b 22 61 75 66 72 6f  6d 22 3a 22 d0 91 d0 b0 :{"aufrom":"�а
00000030  d1 80 d1 81 d1 83 d1 87  d0 b5 d0 bb d0 bb d0 be ����елло

# formatversion=1
00000000  7b 22 62 61 74 63 68 63  6f 6d 70 6c 65 74 65 22 {"batchcomplete"
00000010  3a 22 22 2c 22 63 6f 6e  74 69 6e 75 65 22 3a 7b :"","continue":{
00000020  22 61 75 66 72 6f 6d 22  3a 22 5c 75 30 34 31 31 "aufrom":"\u0411
00000030  5c 75 30 34 33 30 5c 75  30 34 34 30 5c 75 30 34 \u0430\u0440\u04
00000040  34 31 5c 75 30 34 34 33  5c 75 30 34 34 37 5c 75 41\u0443\u0447\u
To be more precise, formatversion=2 is normal/boring/genuine UTF-8, and formatversion=1 is US-ASCII (which is a proper subset of UTF-8, this means any file in US-ASCII is also valid UTF-8). formatversion=1 achieves this goal by not using character literals in the encoded JSON, instead it uses the \u character escapes (which by design use octets from the US-ASCII repertoire only: the backslash, the small letter u, and digits 0 to 9).

Got that? There are two layers of encoding at play here. Both files/responses are UTF-8, therefore the use of the decode_json function, which expects UTF-8 octets as input, is appropriate for both. The function first decodes UTF-8 octets into Perl characters, but it then also decodes JSON \u character escapes into Perl characters.

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Re^4: Is there some universal Unicode+UTF8 switch?
by VK (Novice) on Sep 02, 2019 at 11:21 UTC

    > I am convinced that you already know "enough to be dangerous", but not enough to arrive at the correctly modelled solution that most other Perl programmers would implement.
    I have to agree on that. The last time I extensively programmed something fully by myself and in Perl - in was one week before the capitulation in the Browser War, November 1998. I am actually surprised by myself to be able to write a working program in 2 days - 20 years after. It is amazing how much stuff can be kept at the backdoor of the mind... I'm fully fluent in Javascript though.
    I'll do break the code into minimum test cases to check all spelled advises and corrections.
    It is rather offtop for the initial question "Is there some universal Unicode+UTF8 switch?" - but if it's ok to continue in the same thread then I will continue here.

      if it's ok to continue in the same thread then I will continue here
      Thread drift is allowed. For good netiquette, also change the title in the reply form.

        >Thread drift is allowed. For good netiquette, also change the title in the reply form.
        OK then. So and first of all I am not a staff developer of Wikipedia, just one of volunteer editors. We needed a script for a set of users willing to get notifications about upcoming internal elections, acting like a daemon (checking every 24 hrs some place and notify if there is something).
        tools.wmflabs.org gives you anything of your choice (Perl, PHP, Python, C#, you name it) in latest stable versions. I don't like Python, have no idea about C#, remember something about Perl - so I did Perl.

        This is to make it clear that the list=allusers query has nothing to do with the actual task. It is only to show the exact data format to query and to expect. The full MediaWiki API help is here: https://ru.wikipedia.org/w/api.php?action=help&uselang=en

        Now... The script has to be able to handle Unicode/UTF-8/whatever literals in the code: so I needed use utf8; It also has to output it in HTML- so I needed binmode STDOUT, ':utf8';
        It also has to receive JSON, decode it, slice it, string compare/replace and all other thing - all with Cyrillic in them. I dropped all (en|de)coding things called in this thread unnecessary so came to:

        #!/usr/bin/perl
        
        use strict;
        use warnings;
        
        use utf8;
        use Encode;
        
        use LWP::UserAgent;
        use HTTP::Request::Common;
        use HTTP::Cookies;
        
        use JSON;
        
        my $browser = LWP::UserAgent->new;
        
        # they ask to use descriptive user-agent - not LWP defaults
        # w:ru:User:Bot_of_the_Seven = https://ru.wikipedia.org/wiki/Участник:Bot_of_the_Seven
        $browser->agent('w:ru:User:Bot_of_the_Seven (LWP like Gecko) We come in peace');
        
        # I need cookies exchange enabled for auth
        # here is doesn't matter but to give full LWP picture:
        $browser->cookie_jar({});
        
        # a very few queries can be done by GET - most of MediaWiki require POST
        # so I do POST all around rather then remember where GET is allowed or not:
        my $response = $browser->request(POST 'https://ru.wikipedia.org/w/api.php',
                {
                    'format' => 'json',
                    'formatversion' => 2,
                    'errorformat' => 'bc',
                        
                    'action' => 'query',
                    'list' => 'allusers',
                    'auactiveusers' => 1,
                    'aulimit' => 10,
                    'aufrom' => 'Б'
                }
            );
        
        my $data = decode_json($response->content);
        
        my $test_scalar = $data->{query}->{allusers}[0]->{name};
        
        my @test_array = @{$data->{query}->{allusers}}[0..2];
        
        display_html($test_array[1]->{name});
        
        
        sub display_html {
        
            my @html = (
                '<!DOCTYPE html>',
                '<html>',
                '<head>',
                '<meta charset="UTF-8">',
                '<title>Мой тест</title>',
                '</head>',
                '<body>',
                shift // 'Статус  ОК', # soft OR: 0 and empty string accepted
                '</body>',
                '</html>'
            );
            
            # to avoid "wide character" warnings:
            binmode STDOUT, ':utf8';
            
            print "Content-Type: text/html; charset=utf-8\n\n";
            
            print join("\n", @html);
        }
        

        Is there anything that might go badly wrong concerning Cyrillic in Unicode/UTF-8?

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