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Fix internal links in POD.
[perl5.git] / lib / utf8.pm
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1package utf8;
2
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3$utf8::hint_bits = 0x00800000;
4
612cfdf2 5our $VERSION = '1.05';
b75c8c73 6
a0ed51b3 7sub import {
d5448623 8 $^H |= $utf8::hint_bits;
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9 $enc{caller()} = $_[1] if $_[1];
10}
11
12sub unimport {
d5448623 13 $^H &= ~$utf8::hint_bits;
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14}
15
16sub AUTOLOAD {
17 require "utf8_heavy.pl";
daf4d4ea 18 goto &$AUTOLOAD if defined &$AUTOLOAD;
bd7017d3 19 require Carp;
daf4d4ea 20 Carp::croak("Undefined subroutine $AUTOLOAD called");
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21}
22
231;
24__END__
25
26=head1 NAME
27
b3419ed8 28utf8 - Perl pragma to enable/disable UTF-8 (or UTF-EBCDIC) in source code
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29
30=head1 SYNOPSIS
31
32 use utf8;
33 no utf8;
34
2c9359a2 35 # Convert a Perl scalar to/from UTF-8.
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36 $num_octets = utf8::upgrade($string);
37 $success = utf8::downgrade($string[, FAIL_OK]);
38
2c9359a2 39 # Change the native bytes of a Perl scalar to/from UTF-8 bytes.
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40 utf8::encode($string);
41 utf8::decode($string);
42
786c9463 43 $flag = utf8::is_utf8(STRING); # since Perl 5.8.1
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44 $flag = utf8::valid(STRING);
45
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46=head1 DESCRIPTION
47
393fec97 48The C<use utf8> pragma tells the Perl parser to allow UTF-8 in the
b3419ed8 49program text in the current lexical scope (allow UTF-EBCDIC on EBCDIC based
70122e76 50platforms). The C<no utf8> pragma tells Perl to switch back to treating
b3419ed8 51the source text as literal bytes in the current lexical scope.
a0ed51b3 52
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53This pragma is primarily a compatibility device. Perl versions
54earlier than 5.6 allowed arbitrary bytes in source code, whereas
55in future we would like to standardize on the UTF-8 encoding for
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56source text.
57
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58B<Do not use this pragma for anything else than telling Perl that your
59script is written in UTF-8.> The utility functions described below are
60useful for their own purposes, but they are not really part of the
61"pragmatic" effect.
62
63708e74 63Until UTF-8 becomes the default format for source text, either this
0f414b95 64pragma or the L<encoding> pragma should be used to recognize UTF-8
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65in the source. When UTF-8 becomes the standard source format, this
66pragma will effectively become a no-op. For convenience in what
67follows the term I<UTF-X> is used to refer to UTF-8 on ASCII and ISO
68Latin based platforms and UTF-EBCDIC on EBCDIC based platforms.
a0ed51b3 69
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70See also the effects of the C<-C> switch and its cousin, the
71C<$ENV{PERL_UNICODE}>, in L<perlrun>.
72
ad0029c4 73Enabling the C<utf8> pragma has the following effect:
a0ed51b3 74
4ac9195f 75=over 4
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76
77=item *
78
393fec97 79Bytes in the source text that have their high-bit set will be treated
ad0029c4 80as being part of a literal UTF-8 character. This includes most
c20e2abd 81literals such as identifier names, string constants, and constant
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82regular expression patterns.
83
84On EBCDIC platforms characters in the Latin 1 character set are
85treated as being part of a literal UTF-EBCDIC character.
a0ed51b3 86
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87=back
88
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89Note 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>
91will be unhappy since the bytes are most probably not well-formed
92UTF-8. If you want to have such bytes and use utf8, you can disable
93utf8 until the end the block (or file, if at top level) by C<no utf8;>.
94
63708e74 95If you want to automatically upgrade your 8-bit legacy bytes to UTF-8,
0f414b95 96use the L<encoding> pragma instead of this pragma. For example, if
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97you want to implicitly upgrade your ISO 8859-1 (Latin-1) bytes to UTF-8
98as 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
104In case you are wondering: yes, C<use encoding 'utf8';> works much
105the same as C<use utf8;>.
106
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107=head2 Utility functions
108
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109The following functions are defined in the C<utf8::> package by the
110Perl core. You do not need to say C<use utf8> to use these and in fact
19b49582 111you should not say that unless you really want to have UTF-8 source code.
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112
113=over 4
114
973655a8 115=item * $num_octets = utf8::upgrade($string)
1b026014 116
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117Converts in-place the octet sequence in the native encoding
118(Latin-1 or EBCDIC) to the equivalent character sequence in I<UTF-X>.
119I<$string> already encoded as characters does no harm.
120Returns the number of octets necessary to represent the string as I<UTF-X>.
121Can be used to make sure that the UTF-8 flag is on,
122so that C<\w> or C<lc()> work as Unicode on strings
123containing characters in the range 0x80-0xFF (on ASCII and
124derivatives).
125
126B<Note that this function does not handle arbitrary encodings.>
127Therefore I<Encode.pm> is recommended for the general purposes.
128
129Affected by the encoding pragma.
1b026014 130
973655a8 131=item * $success = utf8::downgrade($string[, FAIL_OK])
1b026014 132
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133Converts in-place the character sequence in I<UTF-X>
134to the equivalent octet sequence in the native encoding (Latin-1 or EBCDIC).
135I<$string> already encoded as octets does no harm.
136Returns true on success. On failure dies or, if the value of
137C<FAIL_OK> is true, returns false.
138Can be used to make sure that the UTF-8 flag is off,
139e.g. when you want to make sure that the substr() or length() function
140works with the usually faster byte algorithm.
141
142B<Note that this function does not handle arbitrary encodings.>
143Therefore I<Encode.pm> is recommended for the general purposes.
144
145B<Not> affected by the encoding pragma.
146
147B<NOTE:> this function is experimental and may change
148or be removed without notice.
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149
150=item * utf8::encode($string)
151
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152Converts in-place the character sequence to the corresponding octet sequence
153in I<UTF-X>. The UTF-8 flag is turned off. Returns nothing.
154
155B<Note that this function does not handle arbitrary encodings.>
156Therefore I<Encode.pm> is recommended for the general purposes.
094ce63c 157
973655a8 158=item * utf8::decode($string)
1b026014 159
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160Attempts to convert in-place the octet sequence in I<UTF-X>
161to the corresponding character sequence. The UTF-8 flag is turned on
162only if the source string contains multiple-byte I<UTF-X> characters.
163If I<$string> is invalid as I<UTF-X>, returns false; otherwise returns true.
164
165B<Note that this function does not handle arbitrary encodings.>
166Therefore I<Encode.pm> is recommended for the general purposes.
167
168B<NOTE:> this function is experimental and may change
169or be removed without notice.
1b026014 170
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171=item * $flag = utf8::is_utf8(STRING)
172
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173(Since Perl 5.8.1) Test whether STRING is in UTF-8. Functionally
174the same as Encode::is_utf8().
8800c35a 175
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176=item * $flag = utf8::valid(STRING)
177
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178[INTERNAL] Test whether STRING is in a consistent state regarding
179UTF-8. Will return true is well-formed UTF-8 and has the UTF-8 flag
180on B<or> if string is held as bytes (both these states are 'consistent').
181Main reason for this routine is to allow Perl's testsuite to check
182that operations have left strings in a consistent state. You most
183probably want to use utf8::is_utf8() instead.
70122e76 184
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185=back
186
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187C<utf8::encode> is like C<utf8::upgrade>, but the UTF8 flag is
188cleared. See L<perlunicode> for more on the UTF8 flag and the C API
189functions C<sv_utf8_upgrade>, C<sv_utf8_downgrade>, C<sv_utf8_encode>,
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190and C<sv_utf8_decode>, which are wrapped by the Perl functions
191C<utf8::upgrade>, C<utf8::downgrade>, C<utf8::encode> and
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192C<utf8::decode>. Note that in the Perl 5.8.0 and 5.8.1 implementation
193the functions utf8::is_utf8, utf8::valid, utf8::encode, utf8::decode,
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194utf8::upgrade, and utf8::downgrade are always available, without a
195C<require utf8> statement-- this may change in future releases.
f1e62f77 196
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197=head1 BUGS
198
199One can have Unicode in identifier names, but not in package/class or
200subroutine names. While some limited functionality towards this does
201exist as of Perl 5.8.0, that is more accidental than designed; use of
202Unicode for the said purposes is unsupported.
203
204One reason of this unfinishedness is its (currently) inherent
205unportability: since both package names and subroutine names may need
206to be mapped to file and directory names, the Unicode capability of
207the filesystem becomes important-- and there unfortunately aren't
208portable answers.
209
393fec97 210=head1 SEE ALSO
a0ed51b3 211
a74e8b45 212L<perluniintro>, L<encoding>, L<perlrun>, L<bytes>, L<perlunicode>
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213
214=cut