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package bytes; |
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our $VERSION = '1.02'; |
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$bytes::hint_bits = 0x00000008; |
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sub import { |
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$^H |= $bytes::hint_bits; |
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} |
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sub unimport { |
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$^H &= ~$bytes::hint_bits; |
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} |
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sub AUTOLOAD { |
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require "bytes_heavy.pl"; |
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goto &$AUTOLOAD if defined &$AUTOLOAD; |
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require Carp; |
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Carp::croak("Undefined subroutine $AUTOLOAD called"); |
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} |
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sub length ($); |
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sub chr ($); |
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sub ord ($); |
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sub substr ($$;$$); |
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sub index ($$;$); |
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sub rindex ($$;$); |
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1; |
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__END__ |
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=head1 NAME |
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bytes - Perl pragma to force byte semantics rather than character semantics |
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=head1 SYNOPSIS |
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use bytes; |
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... chr(...); # or bytes::chr |
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... index(...); # or bytes::index |
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... length(...); # or bytes::length |
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... ord(...); # or bytes::ord |
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... rindex(...); # or bytes::rindex |
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... substr(...); # or bytes::substr |
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no bytes; |
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=head1 DESCRIPTION |
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The C<use bytes> pragma disables character semantics for the rest of the |
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lexical scope in which it appears. C<no bytes> can be used to reverse |
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the effect of C<use bytes> within the current lexical scope. |
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Perl normally assumes character semantics in the presence of character |
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data (i.e. data that has come from a source that has been marked as |
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being of a particular character encoding). When C<use bytes> is in |
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effect, the encoding is temporarily ignored, and each string is treated |
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as a series of bytes. |
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As an example, when Perl sees C<$x = chr(400)>, it encodes the character |
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in UTF-8 and stores it in $x. Then it is marked as character data, so, |
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for instance, C<length $x> returns C<1>. However, in the scope of the |
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C<bytes> pragma, $x is treated as a series of bytes - the bytes that make |
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up the UTF8 encoding - and C<length $x> returns C<2>: |
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$x = chr(400); |
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print "Length is ", length $x, "\n"; # "Length is 1" |
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printf "Contents are %vd\n", $x; # "Contents are 400" |
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{ |
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use bytes; # or "require bytes; bytes::length()" |
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print "Length is ", length $x, "\n"; # "Length is 2" |
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printf "Contents are %vd\n", $x; # "Contents are 198.144" |
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} |
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chr(), ord(), substr(), index() and rindex() behave similarly. |
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For more on the implications and differences between character |
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semantics and byte semantics, see L<perluniintro> and L<perlunicode>. |
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=head1 LIMITATIONS |
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bytes::substr() does not work as an lvalue(). |
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=head1 SEE ALSO |
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L<perluniintro>, L<perlunicode>, L<utf8> |
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=cut |
