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Re^3: DBD::Pg encodes Perlstring to UTF-8 bytes instead of WIN1252 regardless client encoding

by ikegami (Pope)
on Mar 27, 2014 at 19:10 UTC ( #1079979=note: print w/replies, xml ) Need Help??


in reply to Re^2: DBD::Pg encodes Perlstring to UTF-8 bytes instead of WIN1252 regardless client encoding
in thread DBD::Pg encodes Perlstring to UTF-8 bytes instead of WIN1252 regardless client encoding

I've looked at DBD::mysql code and I cannot see anything that explains your "it's as if you actually passed".

Does it use SvPV(sv) without checking separate handling based on SvUTF8(sv)? It might do by using the default char* typemap (e.g. void xsfunc(char* s) { ... }).

As you can see, the following C function is equivalent to that code:

use strict; use warnings; use Test::More; use Encode qw( is_utf8 encode_utf8 ); use Inline C => <<'__EOC__'; void candidate(SV* sv) { dXSARGS; STRLEN len; char* buf = SvPV(sv, len); SP[0] = sv_2mortal(newSVpvn(buf, len)); XSRETURN(1); } __EOC__ sub baseline { is_utf8($_[0]) ? encode_utf8($_[0]) : $_[0] } sub _u { my ($s) = @_; utf8::upgrade($s); $s } sub _d { my ($s) = @_; utf8::downgrade($s); $s } sub printable { sprintf("%v04X", $_[0]) } my @tests = ( [ '00-7F', "a" ], [ '80-FF,UTF8=0', _d(chr(0xE9)) ], [ '80-FF,UTF8=1', _u(chr(0xE9)) ], [ '>FF', chr(0x2660) ], ); plan tests => 0+@tests; for (@tests) { my ($test_name, $input) = @$_; my $got = candidate($input); my $expected = baseline($input); #is($got, $expected, $test_name); is(printable($got), printable($expected), $test_name); }
1..4 ok 1 - 00-7F ok 2 - 80-FF,UTF8=0 ok 3 - 80-FF,UTF8=1 ok 4 - >FF

I'm really interested in this from the point of another DBD maintainer.

Using the same configuration for all tests, can you roundtrip all of the strings mentioned earlier (as verified by is or eq)?

my @tests = ( [ '00-7F', "a" ], [ '80-FF,UTF8=0', _d(chr(0xE9)) ], [ '80-FF,UTF8=1', _u(chr(0xE9)) ], [ '>FF', chr(0x2660) ], ); plan tests => 0+@tests; my $dbh = ... connect and setup as you wish ... my $sth = $dbh->prepare('SELECT ?'); for (@tests) { my ($test_name, $input) = @$_; $sth->execute($input) or die; my $row = $sth->fetch() or die; $sth->finish() or die if $row; my $got = $row->[0]; is(printable($got), printable($input), $test_name); }
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[Eily]: you could tie a variable into not having the same value each time, if you like to make people who try to debug your code facepalm
[Corion]: perl -wle 'package o; use overload q("") => sub {warn "str"; ""}, bool => sub{warn "bool"; 1}; package main; my $o={}; bless $o => o; print "Yay" if ($o && !length($o))'
[Corion]: But people writing such code should document the objects they construct and why it makes sense for an object to be invisible as string while being true in a boolean context
[hippo]: That's equal parts clever and horrendous.
[Eily]: the overload version wouldn't return true with "$x" && !length $x though, I guess
[hippo]: The more I look at this code, the more $x is a plain old scalar and the more this condition will never be true. I'm calling it a bug at this point.
[hippo]: Thanks for your input which has soothed my sanity (a little)
[Corion]: Eily: Sure - if you force both things into stringy things, then you break that magic. But that would also mean that you changed the expression, as now $x = 0.00 will be true instead of false as it were before
[Corion]: Ah no, at least in my feeble experiments that doesn't change the meaning
[Corion]: We sell sanity in small packages ;)

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