5 $bytes::hint_bits = 0x00000008;
8 $^H |= $bytes::hint_bits;
12 $^H &= ~$bytes::hint_bits;
16 require "bytes_heavy.pl";
17 goto &$AUTOLOAD if defined &$AUTOLOAD;
19 Carp::croak("Undefined subroutine $AUTOLOAD called");
34 bytes - Perl pragma to expose the individual bytes of characters
38 Because the bytes pragma breaks encapsulation (i.e. it exposes the innards of
39 how the perl executable currently happens to store a string), the byte values
40 that result are in an unspecified encoding.
42 B<Use of this module for anything other than debugging purposes is
43 strongly discouraged.> If you feel that the functions here within
44 might be useful for your application, this possibly indicates a
45 mismatch between your mental model of Perl Unicode and the current
46 reality. In that case, you may wish to read some of the perl Unicode
47 documentation: L<perluniintro>, L<perlunitut>, L<perlunifaq> and
53 ... chr(...); # or bytes::chr
54 ... index(...); # or bytes::index
55 ... length(...); # or bytes::length
56 ... ord(...); # or bytes::ord
57 ... rindex(...); # or bytes::rindex
58 ... substr(...); # or bytes::substr
64 Perl's characters are stored internally as sequences of one or more bytes.
65 This pragma allows for the examination of the individual bytes that together
68 Originally the pragma was designed for the loftier goal of helping incorporate
69 Unicode into Perl, but the approach that used it was found to be defective,
70 and the one remaining legitimate use is for debugging when you need to
71 non-destructively examine characters' individual bytes. Just insert this
72 pragma temporarily, and remove it after the debugging is finished.
74 The original usage can be accomplished by explicit (rather than this pragma's
75 implict) encoding using the L<Encode> module:
77 use Encode qw/encode/;
79 my $utf8_byte_string = encode "UTF8", $string;
80 my $latin1_byte_string = encode "Latin1", $string;
82 Or, if performance is needed and you are only interested in the UTF-8
87 utf8::encode(my $utf8_byte_string = $string);
89 C<no bytes> can be used to reverse the effect of C<use bytes> within the
90 current lexical scope.
92 As an example, when Perl sees C<$x = chr(400)>, it encodes the character
93 in UTF-8 and stores it in C<$x>. Then it is marked as character data, so,
94 for instance, C<length $x> returns C<1>. However, in the scope of the
95 C<bytes> pragma, C<$x> is treated as a series of bytes - the bytes that make
96 up the UTF8 encoding - and C<length $x> returns C<2>:
99 print "Length is ", length $x, "\n"; # "Length is 1"
100 printf "Contents are %vd\n", $x; # "Contents are 400"
102 use bytes; # or "require bytes; bytes::length()"
103 print "Length is ", length $x, "\n"; # "Length is 2"
104 printf "Contents are %vd\n", $x; # "Contents are 198.144 (on
108 C<chr()>, C<ord()>, C<substr()>, C<index()> and C<rindex()> behave similarly.
110 For more on the implications, see L<perluniintro> and L<perlunicode>.
112 C<bytes::length()> is admittedly handy if you need to know the
113 B<byte length> of a Perl scalar. But a more modern way is:
116 length(encode('UTF-8', $scalar))
120 C<bytes::substr()> does not work as an I<lvalue()>.
124 L<perluniintro>, L<perlunicode>, L<utf8>, L<Encode>