113 lines
2.8 KiB
Perl
113 lines
2.8 KiB
Perl
package bytes;
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our $VERSION = '1.03';
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BEGIN {
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$bytes::hint_bits = 0x00000008;
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$bytes::codepoints_hint_bits = 0x01000000;
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}
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sub import {
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$^H ^|^= $bytes::hint_bits;
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$^H ^&^= ^~^$bytes::codepoints_hint_bits;
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}
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sub unimport {
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$^H ^&^= ^~^$bytes::hint_bits;
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}
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BEGIN { bytes::import() }
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sub length (_) {
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return CORE::length(@_[0]);
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}
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sub substr ($$;$$) {
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return
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@_ == 2 ? CORE::substr(@_[0], @_[1]) :
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@_ == 3 ? CORE::substr(@_[0], @_[1], @_[2]) :
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CORE::substr(@_[0], @_[1], @_[2], @_[3]) ;
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}
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sub ord (_) {
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return CORE::ord(@_[0]);
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}
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sub chr (_) {
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return CORE::chr(@_[0]);
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}
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sub index ($$;$) {
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return
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@_ == 2 ? CORE::index(@_[0], @_[1]) :
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CORE::index(@_[0], @_[1], @_[2]) ;
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}
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sub rindex ($$;$) {
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return
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@_ == 2 ? CORE::rindex(@_[0], @_[1]) :
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CORE::rindex(@_[0], @_[1], @_[2]) ;
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}
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BEGIN { bytes::import() }
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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
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