lib/perl5/5.8.8/utf8.pm

   1 package utf8;
   2
   3 $utf8::hint_bits = 0x00800000;
   4
   5 our $VERSION = '1.06';
   6
   7 sub import {
   8     $^H |= $utf8::hint_bits;
   9     $enc{caller()} = $_[1] if $_[1];
  10 }
  11
  12 sub unimport {
  13     $^H &= ~$utf8::hint_bits;
  14 }
  15
  16 sub AUTOLOAD {
  17     require "utf8_heavy.pl";
  18     goto &$AUTOLOAD if defined &$AUTOLOAD;
  19     require Carp;
  20     Carp::croak("Undefined subroutine $AUTOLOAD called");
  21 }
  22
  23 1;
  24 __END__
  25
  26 =head1 NAME
  27
  28 utf8 - Perl pragma to enable/disable UTF-8 (or UTF-EBCDIC) in source code
  29
  30 =head1 SYNOPSIS
  31
  32     use utf8;
  33     no utf8;
  34
  35     # Convert a Perl scalar to/from UTF-8.
  36     $num_octets = utf8::upgrade($string);
  37     $success    = utf8::downgrade($string[, FAIL_OK]);
  38
  39     # Change the native bytes of a Perl scalar to/from UTF-8 bytes.
  40     utf8::encode($string);
  41     utf8::decode($string);
  42
  43     $flag = utf8::is_utf8(STRING); # since Perl 5.8.1
  44     $flag = utf8::valid(STRING);
  45
  46 =head1 DESCRIPTION
  47
  48 The C<use utf8> pragma tells the Perl parser to allow UTF-8 in the
  49 program text in the current lexical scope (allow UTF-EBCDIC on EBCDIC based
  50 platforms).  The C<no utf8> pragma tells Perl to switch back to treating
  51 the source text as literal bytes in the current lexical scope.
  52
  53 This pragma is primarily a compatibility device.  Perl versions
  54 earlier than 5.6 allowed arbitrary bytes in source code, whereas
  55 in future we would like to standardize on the UTF-8 encoding for
  56 source text.
  57
  58 B<Do not use this pragma for anything else than telling Perl that your
  59 script is written in UTF-8.> The utility functions described below are
  60 useful for their own purposes, but they are not really part of the
  61 "pragmatic" effect.
  62
  63 Until UTF-8 becomes the default format for source text, either this
  64 pragma or the L<encoding> pragma should be used to recognize UTF-8
  65 in the source.  When UTF-8 becomes the standard source format, this
  66 pragma will effectively become a no-op.  For convenience in what
  67 follows the term I<UTF-X> is used to refer to UTF-8 on ASCII and ISO
  68 Latin based platforms and UTF-EBCDIC on EBCDIC based platforms.
  69
  70 See also the effects of the C<-C> switch and its cousin, the
  71 C<$ENV{PERL_UNICODE}>, in L<perlrun>.
  72
  73 Enabling the C<utf8> pragma has the following effect:
  74
  75 =over 4
  76
  77 =item *
  78
  79 Bytes in the source text that have their high-bit set will be treated
  80 as being part of a literal UTF-8 character.  This includes most
  81 literals such as identifier names, string constants, and constant
  82 regular expression patterns.
  83
  84 On EBCDIC platforms characters in the Latin 1 character set are
  85 treated as being part of a literal UTF-EBCDIC character.
  86
  87 =back
  88
  89 Note that if you have bytes with the eighth bit on in your script
  90 (for example embedded Latin-1 in your string literals), C<use utf8>
  91 will be unhappy since the bytes are most probably not well-formed
  92 UTF-8.  If you want to have such bytes and use utf8, you can disable
  93 utf8 until the end the block (or file, if at top level) by C<no utf8;>.
  94
  95 If you want to automatically upgrade your 8-bit legacy bytes to UTF-8,
  96 use the L<encoding> pragma instead of this pragma.  For example, if
  97 you want to implicitly upgrade your ISO 8859-1 (Latin-1) bytes to UTF-8
  98 as used in e.g. C<chr()> and C<\x{...}>, try this:
  99
 100     use encoding "latin-1";
 101     my $c = chr(0xc4);
 102     my $x = "\x{c5}";
 103
 104 In case you are wondering: yes, C<use encoding 'utf8';> works much
 105 the same as C<use utf8;>.
 106
 107 =head2 Utility functions
 108
 109 The following functions are defined in the C<utf8::> package by the
 110 Perl core.  You do not need to say C<use utf8> to use these and in fact
 111 you should not say that  unless you really want to have UTF-8 source code.
 112
 113 =over 4
 114
 115 =item * $num_octets = utf8::upgrade($string)
 116
 117 Converts in-place the octet sequence in the native encoding
 118 (Latin-1 or EBCDIC) to the equivalent character sequence in I<UTF-X>.
 119 I<$string> already encoded as characters does no harm.
 120 Returns the number of octets necessary to represent the string as I<UTF-X>.
 121 Can be used to make sure that the UTF-8 flag is on,
 122 so that C<\w> or C<lc()> work as Unicode on strings
 123 containing characters in the range 0x80-0xFF (on ASCII and
 124 derivatives).
 125
 126 B<Note that this function does not handle arbitrary encodings.>
 127 Therefore I<Encode.pm> is recommended for the general purposes.
 128
 129 Affected by the encoding pragma.
 130
 131 =item * $success = utf8::downgrade($string[, FAIL_OK])
 132
 133 Converts in-place the character sequence in I<UTF-X>
 134 to the equivalent octet sequence in the native encoding (Latin-1 or EBCDIC).
 135 I<$string> already encoded as octets does no harm.
 136 Returns true on success. On failure dies or, if the value of
 137 C<FAIL_OK> is true, returns false.
 138 Can be used to make sure that the UTF-8 flag is off,
 139 e.g. when you want to make sure that the substr() or length() function
 140 works with the usually faster byte algorithm.
 141
 142 B<Note that this function does not handle arbitrary encodings.>
 143 Therefore I<Encode.pm> is recommended for the general purposes.
 144
 145 B<Not> affected by the encoding pragma.
 146
 147 B<NOTE:> this function is experimental and may change
 148 or be removed without notice.
 149
 150 =item * utf8::encode($string)
 151
 152 Converts in-place the character sequence to the corresponding octet sequence
 153 in I<UTF-X>.  The UTF-8 flag is turned off.  Returns nothing.
 154
 155 B<Note that this function does not handle arbitrary encodings.>
 156 Therefore I<Encode.pm> is recommended for the general purposes.
 157
 158 =item * utf8::decode($string)
 159
 160 Attempts to convert in-place the octet sequence in I<UTF-X>
 161 to the corresponding character sequence.  The UTF-8 flag is turned on
 162 only if the source string contains multiple-byte I<UTF-X> characters.
 163 If I<$string> is invalid as I<UTF-X>, returns false; otherwise returns true.
 164
 165 B<Note that this function does not handle arbitrary encodings.>
 166 Therefore I<Encode.pm> is recommended for the general purposes.
 167
 168 B<NOTE:> this function is experimental and may change
 169 or be removed without notice.
 170
 171 =item * $flag = utf8::is_utf8(STRING)
 172
 173 (Since Perl 5.8.1)  Test whether STRING is in UTF-8.  Functionally
 174 the same as Encode::is_utf8().
 175
 176 =item * $flag = utf8::valid(STRING)
 177
 178 [INTERNAL] Test whether STRING is in a consistent state regarding
 179 UTF-8.  Will return true is well-formed UTF-8 and has the UTF-8 flag
 180 on B<or> if string is held as bytes (both these states are 'consistent').
 181 Main reason for this routine is to allow Perl's testsuite to check
 182 that operations have left strings in a consistent state.  You most
 183 probably want to use utf8::is_utf8() instead.
 184
 185 =back
 186
 187 C<utf8::encode> is like C<utf8::upgrade>, but the UTF8 flag is
 188 cleared.  See L<perlunicode> for more on the UTF8 flag and the C API
 189 functions C<sv_utf8_upgrade>, C<sv_utf8_downgrade>, C<sv_utf8_encode>,
 190 and C<sv_utf8_decode>, which are wrapped by the Perl functions
 191 C<utf8::upgrade>, C<utf8::downgrade>, C<utf8::encode> and
 192 C<utf8::decode>.  Note that in the Perl 5.8.0 and 5.8.1 implementation
 193 the functions utf8::is_utf8, utf8::valid, utf8::encode, utf8::decode,
 194 utf8::upgrade, and utf8::downgrade are always available, without a
 195 C<require utf8> statement-- this may change in future releases.
 196
 197 =head1 BUGS
 198
 199 One can have Unicode in identifier names, but not in package/class or
 200 subroutine names.  While some limited functionality towards this does
 201 exist as of Perl 5.8.0, that is more accidental than designed; use of
 202 Unicode for the said purposes is unsupported.
 203
 204 One reason of this unfinishedness is its (currently) inherent
 205 unportability: since both package names and subroutine names may need
 206 to be mapped to file and directory names, the Unicode capability of
 207 the filesystem becomes important-- and there unfortunately aren't
 208 portable answers.
 209
 210 =head1 SEE ALSO
 211
 212 L<perluniintro>, L<encoding>, L<perlrun>, L<bytes>, L<perlunicode>
 213
 214 =cut