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Diffstat (limited to 'Master/perltl/lib/bytes.pm')
-rw-r--r-- | Master/perltl/lib/bytes.pm | 68 |
1 files changed, 68 insertions, 0 deletions
diff --git a/Master/perltl/lib/bytes.pm b/Master/perltl/lib/bytes.pm new file mode 100644 index 00000000000..cd82abc75b5 --- /dev/null +++ b/Master/perltl/lib/bytes.pm @@ -0,0 +1,68 @@ +package bytes; + +our $VERSION = '1.00'; + +$bytes::hint_bits = 0x00000008; + +sub import { + $^H |= $bytes::hint_bits; +} + +sub unimport { + $^H &= ~$bytes::hint_bits; +} + +sub AUTOLOAD { + require "bytes_heavy.pl"; + goto &$AUTOLOAD; +} + +sub length ($); + +1; +__END__ + +=head1 NAME + +bytes - Perl pragma to force byte semantics rather than character semantics + +=head1 SYNOPSIS + + use bytes; + 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; + print "Length is ", length $x, "\n"; # "Length is 2" + printf "Contents are %vd\n", $x; # "Contents are 198.144" + } + +For more on the implications and differences between character +semantics and byte semantics, see L<perlunicode>. + +=head1 SEE ALSO + +L<perlunicode>, L<utf8> + +=cut |