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package bytes;
our $VERSION = '1.03';
$bytes::hint_bits = 0x00000008;
sub import {
$^H |= $bytes::hint_bits;
}
sub unimport {
$^H &= ~$bytes::hint_bits;
}
sub AUTOLOAD {
require "bytes_heavy.pl";
goto &$AUTOLOAD if defined &$AUTOLOAD;
require Carp;
Carp::croak("Undefined subroutine $AUTOLOAD called");
}
sub length (_);
sub chr (_);
sub ord (_);
sub substr ($$;$$);
sub index ($$;$);
sub rindex ($$;$);
1;
__END__
=head1 NAME
bytes - Perl pragma to force byte semantics rather than character semantics
=head1 SYNOPSIS
use bytes;
... chr(...); # or bytes::chr
... index(...); # or bytes::index
... length(...); # or bytes::length
... ord(...); # or bytes::ord
... rindex(...); # or bytes::rindex
... substr(...); # or bytes::substr
no bytes;
=head1 DESCRIPTION
The C<use bytes> pragma disables character semantics for the rest of the
lexical scope in which it appears. C<no bytes> can be used to reverse
the effect of C<use bytes> within the current lexical scope.
Perl normally assumes character semantics in the presence of character
data (i.e. data that has come from a source that has been marked as
being of a particular character encoding). When C<use bytes> is in
effect, the encoding is temporarily ignored, and each string is treated
as a series of bytes.
As an example, when Perl sees C<$x = chr(400)>, it encodes the character
in UTF-8 and stores it in $x. Then it is marked as character data, so,
for instance, C<length $x> returns C<1>. However, in the scope of the
C<bytes> pragma, $x is treated as a series of bytes - the bytes that make
up the UTF8 encoding - and C<length $x> returns C<2>:
$x = chr(400);
print "Length is ", length $x, "\n"; # "Length is 1"
printf "Contents are %vd\n", $x; # "Contents are 400"
{
use bytes; # or "require bytes; bytes::length()"
print "Length is ", length $x, "\n"; # "Length is 2"
printf "Contents are %vd\n", $x; # "Contents are 198.144"
}
chr(), ord(), substr(), index() and rindex() behave similarly.
For more on the implications and differences between character
semantics and byte semantics, see L<perluniintro> and L<perlunicode>.
=head1 LIMITATIONS
bytes::substr() does not work as an lvalue().
=head1 SEE ALSO
L<perluniintro>, L<perlunicode>, L<utf8>
=cut
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