NAME¶
Encode::Alias - alias definitions to encodings
SYNOPSIS¶
use Encode;
use Encode::Alias;
define_alias( "newName" => ENCODING);
define_alias( qr/.../ => ENCODING);
define_alias( sub { return ENCODING if ...; } );
DESCRIPTION¶
Allows newName to be used as an alias for ENCODING. ENCODING may be either the
name of an encoding or an encoding object (as described in Encode).
Currently the first argument to
define_alias() can be specified in the
following ways:
- As a simple string.
- As a qr// compiled regular expression, e.g.:
-
define_alias( qr/^iso8859-(\d+)$/i => '"iso-8859-$1"' );
In this case, if ENCODING is not a reference, it is
"eval"-ed in order to allow $1 etc. to be substituted. The
example is one way to alias names as used in X11 fonts to the MIME names
for the iso-8859-* family. Note the double quotes inside the single
quotes.
(or, you don't have to do this yourself because this example is predefined)
If you are using a regex here, you have to use the quotes as shown or it
won't work. Also note that regex handling is tricky even for the
experienced. Use this feature with caution.
- As a code reference, e.g.:
-
define_alias( sub {shift =~ /^iso8859-(\d+)$/i ? "iso-8859-$1" : undef } );
The same effect as the example above in a different way. The coderef takes
the alias name as an argument and returns a canonical name on success or
undef if not. Note the second argument is ignored if provided. Use this
with even more caution than the regex version.
Changes in code reference aliasing
As of Encode 1.87, the older form
define_alias( sub { return /^iso8859-(\d+)$/i ? "iso-8859-$1" : undef } );
no longer works.
Encode up to 1.86 internally used "local $_" to implement this older
form. But consider the code below;
use Encode;
$_ = "eeeee" ;
while (/(e)/g) {
my $utf = decode('aliased-encoding-name', $1);
print "position:",pos,"\n";
}
Prior to Encode 1.86 this fails because of "local $_".
Alias overloading¶
You can override predefined aliases by simply applying
define_alias().
The new alias is always evaluated first, and when necessary,
define_alias() flushes the internal cache to make the new definition
available.
# redirect SHIFT_JIS to MS/IBM Code Page 932, which is a
# superset of SHIFT_JIS
define_alias( qr/shift.*jis$/i => '"cp932"' );
define_alias( qr/sjis$/i => '"cp932"' );
If you want to zap all predefined aliases, you can use
Encode::Alias->undef_aliases;
to do so. And
Encode::Alias->init_aliases;
gets the factory settings back.
Note that
define_alias() will not be able to override the canonical name
of encodings. Encodings are first looked up by canonical name before potential
aliases are tried.
SEE ALSO¶
Encode, Encode::Supported