1 | package bytes;
|
---|
2 |
|
---|
3 | our $VERSION = '1.02';
|
---|
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
|
---|