On Wed, 7 Dec 2011, Junio C Hamano wrote:
> Jakub Narebski <jnareb@xxxxxxxxx> writes:
>
> > But doing this would change gitweb behavior. Currently when
> > encountering something (usually line of output) that is not valid
> > UTF-8, we decode it (to UTF-8) using $fallback_encoding, by default
> > 'latin1'. Note however that this value is per gitweb installation,
> > not per repository.
>
> I think we added and you acked 00f429a (gitweb: Handle non UTF-8 text
> better, 2007-06-03) for a good reason, and I think the above argues that
> whatever issue the commit tried to address is a non-issue. Is it really
> true?
Actually... the change in
00f429a (gitweb: Handle non UTF-8 text better, 2007-06-03)
worked correctly, but since
e5d3de5 (gitweb: use Perl built-in utf8 function for UTF-8 decoding., 2007-12-04)
it was changed to a NON-WORKING version - and *nobody* protested.
sub to_utf8 {
my $str = shift;
- my $res;
- eval { $res = decode_utf8($str, Encode::FB_CROAK); };
- if (defined $res) {
- return $res;
+ if (utf8::valid($str)) {
+ utf8::decode($str);
+ return $str;
} else {
return decode($fallback_encoding, $str, Encode::FB_DEFAULT);
}
Well, it works for utf8 and latin1 _only_ (with $fallback_encoding being
set to 'latin1' by default), and for latin1 by historical accident... that
might be why nobody noticed. $fallback_encoding != 'latin1' or 'utf8'
didn't work.
utf8::valid(STRING) is an internal function that tests whether STRING is
in a consistent state regarding UTF-8. It returns true is well-formed
UTF-8 and has the UTF-8 flag on _or_ if string is held as bytes (both
these states are 'consistent'). For gitweb the second option was true.
Note that utf8:decode(STRING) returns false if STRING is invalid as UTF-8.
What makes it all work is the fact that utf8:decode(STRING) turns on UTF-8
flag only if source string is valid UTF-8 and contains multi-byte UTF-8
characters... and that if string doesn't have UTF-8 flag set it is treated
as in native Perl encoding, i.e. 'latin1' / 'iso-8859-1' (unless it is EBCDIC).
It is ':utf8' layer that actually convert 'latin1' to 'utf8'.
-- >8 --
Subject: [PATCH] gitweb: Fix fallback mode of to_utf8 subroutine
e5d3de5 (gitweb: use Perl built-in utf8 function for UTF-8 decoding.,
2007-12-04) was meant to make gitweb faster by using Perl's internals
(see subsection "Messing with Perl's Internals" in Encode(3pm) manpage)
Simple benchmark confirms that (old = 00f429a, new = this version):
old new
old -- -65%
new 189% --
Unfortunately it made fallback mode of to_utf8 do not work... except
for default value 'latin1' of $fallback_encoding ('latin1' is Perl
native encoding), which is why it was not noticed for such long time.
utf8::valid(STRING) is an internal function that tests whether STRING
is in a _consistent state_ regarding UTF-8. It returns true is
well-formed UTF-8 and has the UTF-8 flag on _*or*_ if string is held
as bytes (both these states are 'consistent'). For gitweb the second
option was true, as output from git commands is opened without ':utf8'
layer.
What made it work at all for STRING in 'latin1' encoding is the fact
that utf8:decode(STRING) turns on UTF-8 flag only if source string is
valid UTF-8 and contains multi-byte UTF-8 characters... and that if
string doesn't have UTF-8 flag set it is treated as in native Perl
encoding, i.e. 'latin1' / 'iso-8859-1' (unless native encoding it is
EBCDIC ;-)). It was ':utf8' layer that actually converted 'latin1'
(no UTF-8 flag == native == 'latin1) to 'utf8'.
Let's make use of the fact that utf8:decode(STRING) returns false if
STRING is invalid as UTF-8 to check whether to enable fallback mode.
Signed-off-by: Jakub Narebski <jnareb@xxxxxxxxx>
---
I'm sorry for overly wordy commit message...
gitweb/gitweb.perl | 3 +--
1 files changed, 1 insertions(+), 2 deletions(-)
diff --git a/gitweb/gitweb.perl b/gitweb/gitweb.perl
index d24763b..75b0970 100755
--- a/gitweb/gitweb.perl
+++ b/gitweb/gitweb.perl
@@ -1443,8 +1443,7 @@ sub validate_refname {
sub to_utf8 {
my $str = shift;
return undef unless defined $str;
- if (utf8::valid($str)) {
- utf8::decode($str);
+ if (utf8::valid($str) && utf8::decode($str)) {
return $str;
} else {
return decode($fallback_encoding, $str, Encode::FB_DEFAULT);
--
1.7.6
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