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   1  package bytes;
   2  
   3  our $VERSION = '1.03';
   4  
   5  $bytes::hint_bits = 0x00000008;
   6  
   7  sub import {
   8      $^H |= $bytes::hint_bits;
   9  }
  10  
  11  sub unimport {
  12      $^H &= ~$bytes::hint_bits;
  13  }
  14  
  15  sub AUTOLOAD {
  16      require  "bytes_heavy.pl";
  17      goto &$AUTOLOAD if defined &$AUTOLOAD;
  18      require Carp;
  19      Carp::croak("Undefined subroutine $AUTOLOAD called");
  20  }
  21  
  22  sub length (_);
  23  sub chr (_);
  24  sub ord (_);
  25  sub substr ($$;$$);
  26  sub index ($$;$);
  27  sub rindex ($$;$);
  28  
  29  1;
  30  __END__
  31  
  32  =head1 NAME
  33  
  34  bytes - Perl pragma to force byte semantics rather than character semantics
  35  
  36  =head1 SYNOPSIS
  37  
  38      use bytes;
  39      ... chr(...);       # or bytes::chr
  40      ... index(...);     # or bytes::index
  41      ... length(...);    # or bytes::length
  42      ... ord(...);       # or bytes::ord
  43      ... rindex(...);    # or bytes::rindex
  44      ... substr(...);    # or bytes::substr
  45      no bytes;
  46  
  47  
  48  =head1 DESCRIPTION
  49  
  50  The C<use bytes> pragma disables character semantics for the rest of the
  51  lexical scope in which it appears.  C<no bytes> can be used to reverse
  52  the effect of C<use bytes> within the current lexical scope.
  53  
  54  Perl normally assumes character semantics in the presence of character
  55  data (i.e. data that has come from a source that has been marked as
  56  being of a particular character encoding). When C<use bytes> is in
  57  effect, the encoding is temporarily ignored, and each string is treated
  58  as a series of bytes. 
  59  
  60  As an example, when Perl sees C<$x = chr(400)>, it encodes the character
  61  in UTF-8 and stores it in $x. Then it is marked as character data, so,
  62  for instance, C<length $x> returns C<1>. However, in the scope of the
  63  C<bytes> pragma, $x is treated as a series of bytes - the bytes that make
  64  up the UTF8 encoding - and C<length $x> returns C<2>:
  65  
  66      $x = chr(400);
  67      print "Length is ", length $x, "\n";     # "Length is 1"
  68      printf "Contents are %vd\n", $x;         # "Contents are 400"
  69      { 
  70          use bytes; # or "require bytes; bytes::length()"
  71          print "Length is ", length $x, "\n"; # "Length is 2"
  72          printf "Contents are %vd\n", $x;     # "Contents are 198.144"
  73      }
  74  
  75  chr(), ord(), substr(), index() and rindex() behave similarly.
  76  
  77  For more on the implications and differences between character
  78  semantics and byte semantics, see L<perluniintro> and L<perlunicode>.
  79  
  80  =head1 LIMITATIONS
  81  
  82  bytes::substr() does not work as an lvalue().
  83  
  84  =head1 SEE ALSO
  85  
  86  L<perluniintro>, L<perlunicode>, L<utf8>
  87  
  88  =cut