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| Current File : //usr/share/perl5/utf8.pm |
package utf8;
$utf8::hint_bits = 0x00800000;
our $VERSION = '1.09';
sub import {
$^H |= $utf8::hint_bits;
$enc{caller()} = $_[1] if $_[1];
}
sub unimport {
$^H &= ~$utf8::hint_bits;
}
sub AUTOLOAD {
require "utf8_heavy.pl";
goto &$AUTOLOAD if defined &$AUTOLOAD;
require Carp;
Carp::croak("Undefined subroutine $AUTOLOAD called");
}
1;
__END__
=head1 NAME
utf8 - Perl pragma to enable/disable UTF-8 (or UTF-EBCDIC) in source code
=head1 SYNOPSIS
use utf8;
no utf8;
# Convert the internal representation of a Perl scalar to/from UTF-8.
$num_octets = utf8::upgrade($string);
$success = utf8::downgrade($string[, FAIL_OK]);
# Change each character of a Perl scalar to/from a series of
# characters that represent the UTF-8 bytes of each original character.
utf8::encode($string); # "\x{100}" becomes "\xc4\x80"
utf8::decode($string); # "\xc4\x80" becomes "\x{100}"
$flag = utf8::is_utf8(STRING); # since Perl 5.8.1
$flag = utf8::valid(STRING);
=head1 DESCRIPTION
The C<use utf8> pragma tells the Perl parser to allow UTF-8 in the
program text in the current lexical scope (allow UTF-EBCDIC on EBCDIC based
platforms). The C<no utf8> pragma tells Perl to switch back to treating
the source text as literal bytes in the current lexical scope.
B<Do not use this pragma for anything else than telling Perl that your
script is written in UTF-8.> The utility functions described below are
directly usable without C<use utf8;>.
Because it is not possible to reliably tell UTF-8 from native 8 bit
encodings, you need either a Byte Order Mark at the beginning of your
source code, or C<use utf8;>, to instruct perl.
When UTF-8 becomes the standard source format, this pragma will
effectively become a no-op. For convenience in what follows the term
I<UTF-X> is used to refer to UTF-8 on ASCII and ISO Latin based
platforms and UTF-EBCDIC on EBCDIC based platforms.
See also the effects of the C<-C> switch and its cousin, the
C<$ENV{PERL_UNICODE}>, in L<perlrun>.
Enabling the C<utf8> pragma has the following effect:
=over 4
=item *
Bytes in the source text that have their high-bit set will be treated
as being part of a literal UTF-X sequence. This includes most
literals such as identifier names, string constants, and constant
regular expression patterns.
On EBCDIC platforms characters in the Latin 1 character set are
treated as being part of a literal UTF-EBCDIC character.
=back
Note that if you have bytes with the eighth bit on in your script
(for example embedded Latin-1 in your string literals), C<use utf8>
will be unhappy since the bytes are most probably not well-formed
UTF-X. If you want to have such bytes under C<use utf8>, you can disable
this pragma until the end the block (or file, if at top level) by
C<no utf8;>.
=head2 Utility functions
The following functions are defined in the C<utf8::> package by the
Perl core. You do not need to say C<use utf8> to use these and in fact
you should not say that unless you really want to have UTF-8 source code.
=over 4
=item * $num_octets = utf8::upgrade($string)
Converts in-place the internal representation of the string from an octet
sequence in the native encoding (Latin-1 or EBCDIC) to I<UTF-X>. The
logical character sequence itself is unchanged. If I<$string> is already
stored as I<UTF-X>, then this is a no-op. Returns the
number of octets necessary to represent the string as I<UTF-X>. Can be
used to make sure that the UTF-8 flag is on, so that C<\w> or C<lc()>
work as Unicode on strings containing characters in the range 0x80-0xFF
(on ASCII and derivatives).
B<Note that this function does not handle arbitrary encodings.>
Therefore Encode is recommended for the general purposes; see also
L<Encode>.
=item * $success = utf8::downgrade($string[, FAIL_OK])
Converts in-place the internal representation of the string from
I<UTF-X> to the equivalent octet sequence in the native encoding (Latin-1
or EBCDIC). The logical character sequence itself is unchanged. If
I<$string> is already stored as native 8 bit, then this is a no-op. Can
be used to
make sure that the UTF-8 flag is off, e.g. when you want to make sure
that the substr() or length() function works with the usually faster
byte algorithm.
Fails if the original I<UTF-X> sequence cannot be represented in the
native 8 bit encoding. On failure dies or, if the value of C<FAIL_OK> is
true, returns false.
Returns true on success.
B<Note that this function does not handle arbitrary encodings.>
Therefore Encode is recommended for the general purposes; see also
L<Encode>.
=item * utf8::encode($string)
Converts in-place the character sequence to the corresponding octet
sequence in I<UTF-X>. That is, every (possibly wide) character gets
replaced with a sequence of one or more characters that represent the
individual I<UTF-X> bytes of the character. The UTF8 flag is turned off.
Returns nothing.
my $a = "\x{100}"; # $a contains one character, with ord 0x100
utf8::encode($a); # $a contains two characters, with ords 0xc4 and 0x80
B<Note that this function does not handle arbitrary encodings.>
Therefore Encode is recommended for the general purposes; see also
L<Encode>.
=item * $success = utf8::decode($string)
Attempts to convert in-place the octet sequence in I<UTF-X> to the
corresponding character sequence. That is, it replaces each sequence of
characters in the string whose ords represent a valid UTF-X byte
sequence, with the corresponding single character. The UTF-8 flag is
turned on only if the source string contains multiple-byte I<UTF-X>
characters. If I<$string> is invalid as I<UTF-X>, returns false;
otherwise returns true.
my $a = "\xc4\x80"; # $a contains two characters, with ords 0xc4 and 0x80
utf8::decode($a); # $a contains one character, with ord 0x100
B<Note that this function does not handle arbitrary encodings.>
Therefore Encode is recommended for the general purposes; see also
L<Encode>.
=item * $flag = utf8::is_utf8(STRING)
(Since Perl 5.8.1) Test whether STRING is in UTF-8 internally.
Functionally the same as Encode::is_utf8().
=item * $flag = utf8::valid(STRING)
[INTERNAL] Test whether STRING is in a consistent state regarding
UTF-8. Will return true is well-formed UTF-8 and has the UTF-8 flag
on B<or> if string is held as bytes (both these states are 'consistent').
Main reason for this routine is to allow Perl's testsuite to check
that operations have left strings in a consistent state. You most
probably want to use utf8::is_utf8() instead.
=back
C<utf8::encode> is like C<utf8::upgrade>, but the UTF8 flag is
cleared. See L<perlunicode> for more on the UTF8 flag and the C API
functions C<sv_utf8_upgrade>, C<sv_utf8_downgrade>, C<sv_utf8_encode>,
and C<sv_utf8_decode>, which are wrapped by the Perl functions
C<utf8::upgrade>, C<utf8::downgrade>, C<utf8::encode> and
C<utf8::decode>. Also, the functions utf8::is_utf8, utf8::valid,
utf8::encode, utf8::decode, utf8::upgrade, and utf8::downgrade are
actually internal, and thus always available, without a C<require utf8>
statement.
=head1 BUGS
One can have Unicode in identifier names, but not in package/class or
subroutine names. While some limited functionality towards this does
exist as of Perl 5.8.0, that is more accidental than designed; use of
Unicode for the said purposes is unsupported.
One reason of this unfinishedness is its (currently) inherent
unportability: since both package names and subroutine names may need
to be mapped to file and directory names, the Unicode capability of
the filesystem becomes important-- and there unfortunately aren't
portable answers.
=head1 SEE ALSO
L<perlunitut>, L<perluniintro>, L<perlrun>, L<bytes>, L<perlunicode>
=cut