lib/perl5/5.6.1/bytes.pm

   1 package bytes;
   2
   3 $bytes::hint_bits = 0x00000008;
   4
   5 sub import {
   6     $^H |= $bytes::hint_bits;
   7 }
   8
   9 sub unimport {
  10     $^H &= ~$bytes::hint_bits;
  11 }
  12
  13 sub AUTOLOAD {
  14     require "bytes_heavy.pl";
  15     goto &$AUTOLOAD;
  16 }
  17
  18 sub length ($);
  19
  20 1;
  21 __END__
  22
  23 =head1 NAME
  24
  25 bytes - Perl pragma to force byte semantics rather than character semantics
  26
  27 =head1 SYNOPSIS
  28
  29     use bytes;
  30     no bytes;
  31
  32 =head1 DESCRIPTION
  33
  34 WARNING: The implementation of Unicode support in Perl is incomplete.
  35 See L<perlunicode> for the exact details.
  36
  37 The C<use bytes> pragma disables character semantics for the rest of the
  38 lexical scope in which it appears.  C<no bytes> can be used to reverse
  39 the effect of C<use bytes> within the current lexical scope.
  40
  41 Perl normally assumes character semantics in the presence of character
  42 data (i.e. data that has come from a source that has been marked as
  43 being of a particular character encoding). When C<use bytes> is in
  44 effect, the encoding is temporarily ignored, and each string is treated
  45 as a series of bytes.
  46
  47 As an example, when Perl sees C<$x = chr(400)>, it encodes the character
  48 in UTF8 and stores it in $x. Then it is marked as character data, so,
  49 for instance, C<length $x> returns C<1>. However, in the scope of the
  50 C<bytes> pragma, $x is treated as a series of bytes - the bytes that make
  51 up the UTF8 encoding - and C<length $x> returns C<2>:
  52
  53     $x = chr(400);
  54     print "Length is ", length $x, "\n";     # "Length is 1"
  55     printf "Contents are %vd\n", $x;         # "Contents are 400"
  56     {
  57         use bytes;
  58         print "Length is ", length $x, "\n"; # "Length is 2"
  59         printf "Contents are %vd\n", $x;     # "Contents are 198.144"
  60     }
  61
  62 For more on the implications and differences between character
  63 semantics and byte semantics, see L<perlunicode>.
  64
  65 =head1 SEE ALSO
  66
  67 L<perlunicode>, L<utf8>
  68
  69 =cut