1package Encode::Unicode; 2 3use strict; 4use warnings; 5no warnings 'redefine'; 6 7our $VERSION = do { my @r = (q$Revision: 1.40 $ =~ /\d+/g); sprintf "%d."."%02d" x $#r, @r }; 8 9use XSLoader; 10XSLoader::load(__PACKAGE__,$VERSION); 11 12# 13# Object Generator 8 transcoders all at once! 14# 15 16require Encode; 17 18our %BOM_Unknown = map {$_ => 1} qw(UTF-16 UTF-32); 19 20for my $name (qw(UTF-16 UTF-16BE UTF-16LE 21 UTF-32 UTF-32BE UTF-32LE 22 UCS-2BE UCS-2LE)) 23{ 24 my ($size, $endian, $ucs2, $mask); 25 $name =~ /^(\w+)-(\d+)(\w*)$/o; 26 if ($ucs2 = ($1 eq 'UCS')){ 27 $size = 2; 28 }else{ 29 $size = $2/8; 30 } 31 $endian = ($3 eq 'BE') ? 'n' : ($3 eq 'LE') ? 'v' : '' ; 32 $size == 4 and $endian = uc($endian); 33 34 $Encode::Encoding{$name} = 35 bless { 36 Name => $name, 37 size => $size, 38 endian => $endian, 39 ucs2 => $ucs2, 40 } => __PACKAGE__; 41} 42 43use base qw(Encode::Encoding); 44 45sub renew { 46 my $self = shift; 47 $BOM_Unknown{$self->name} or return $self; 48 my $clone = bless { %$self } => ref($self); 49 $clone->{clone} = 1; # so the caller knows it is renewed. 50 return $clone; 51} 52 53# There used to be a perl implemntation of (en|de)code but with 54# XS version is ripe, perl version is zapped for optimal speed 55 56*decode = \&decode_xs; 57*encode = \&encode_xs; 58 591; 60__END__ 61 62=head1 NAME 63 64Encode::Unicode -- Various Unicode Transformation Formats 65 66=cut 67 68=head1 SYNOPSIS 69 70 use Encode qw/encode decode/; 71 $ucs2 = encode("UCS-2BE", $utf8); 72 $utf8 = decode("UCS-2BE", $ucs2); 73 74=head1 ABSTRACT 75 76This module implements all Character Encoding Schemes of Unicode that 77are officially documented by Unicode Consortium (except, of course, 78for UTF-8, which is a native format in perl). 79 80=over 4 81 82=item L<http://www.unicode.org/glossary/> says: 83 84I<Character Encoding Scheme> A character encoding form plus byte 85serialization. There are Seven character encoding schemes in Unicode: 86UTF-8, UTF-16, UTF-16BE, UTF-16LE, UTF-32 (UCS-4), UTF-32BE (UCS-4BE) and 87UTF-32LE (UCS-4LE), and UTF-7. 88 89Since UTF-7 is a 7-bit (re)encoded version of UTF-16BE, It is not part of 90Unicode's Character Encoding Scheme. It is separately implemented in 91Encode::Unicode::UTF7. For details see L<Encode::Unicode::UTF7>. 92 93=item Quick Reference 94 95 Decodes from ord(N) Encodes chr(N) to... 96 octet/char BOM S.P d800-dfff ord > 0xffff \x{1abcd} == 97 ---------------+-----------------+------------------------------ 98 UCS-2BE 2 N N is bogus Not Available 99 UCS-2LE 2 N N bogus Not Available 100 UTF-16 2/4 Y Y is S.P S.P BE/LE 101 UTF-16BE 2/4 N Y S.P S.P 0xd82a,0xdfcd 102 UTF-16LE 2 N Y S.P S.P 0x2ad8,0xcddf 103 UTF-32 4 Y - is bogus As is BE/LE 104 UTF-32BE 4 N - bogus As is 0x0001abcd 105 UTF-32LE 4 N - bogus As is 0xcdab0100 106 UTF-8 1-4 - - bogus >= 4 octets \xf0\x9a\af\8d 107 ---------------+-----------------+------------------------------ 108 109=back 110 111=head1 Size, Endianness, and BOM 112 113You can categorize these CES by 3 criteria: size of each character, 114endianness, and Byte Order Mark. 115 116=head2 by size 117 118UCS-2 is a fixed-length encoding with each character taking 16 bits. 119It B<does not> support I<surrogate pairs>. When a surrogate pair 120is encountered during decode(), its place is filled with \x{FFFD} 121if I<CHECK> is 0, or the routine croaks if I<CHECK> is 1. When a 122character whose ord value is larger than 0xFFFF is encountered, 123its place is filled with \x{FFFD} if I<CHECK> is 0, or the routine 124croaks if I<CHECK> is 1. 125 126UTF-16 is almost the same as UCS-2 but it supports I<surrogate pairs>. 127When it encounters a high surrogate (0xD800-0xDBFF), it fetches the 128following low surrogate (0xDC00-0xDFFF) and C<desurrogate>s them to 129form a character. Bogus surrogates result in death. When \x{10000} 130or above is encountered during encode(), it C<ensurrogate>s them and 131pushes the surrogate pair to the output stream. 132 133UTF-32 (UCS-4) is a fixed-length encoding with each character taking 32 bits. 134Since it is 32-bit, there is no need for I<surrogate pairs>. 135 136=head2 by endianness 137 138The first (and now failed) goal of Unicode was to map all character 139repertoires into a fixed-length integer so that programmers are happy. 140Since each character is either a I<short> or I<long> in C, you have to 141pay attention to the endianness of each platform when you pass data 142to one another. 143 144Anything marked as BE is Big Endian (or network byte order) and LE is 145Little Endian (aka VAX byte order). For anything not marked either 146BE or LE, a character called Byte Order Mark (BOM) indicating the 147endianness is prepended to the string. 148 149=over 4 150 151=item BOM as integer when fetched in network byte order 152 153 16 32 bits/char 154 ------------------------- 155 BE 0xFeFF 0x0000FeFF 156 LE 0xFFeF 0xFFFe0000 157 ------------------------- 158 159=back 160 161This modules handles the BOM as follows. 162 163=over 4 164 165=item * 166 167When BE or LE is explicitly stated as the name of encoding, BOM is 168simply treated as a normal character (ZERO WIDTH NO-BREAK SPACE). 169 170=item * 171 172When BE or LE is omitted during decode(), it checks if BOM is at the 173beginning of the string; if one is found, the endianness is set to 174what the BOM says. If no BOM is found, the routine dies. 175 176=item * 177 178When BE or LE is omitted during encode(), it returns a BE-encoded 179string with BOM prepended. So when you want to encode a whole text 180file, make sure you encode() the whole text at once, not line by line 181or each line, not file, will have a BOM prepended. 182 183=item * 184 185C<UCS-2> is an exception. Unlike others, this is an alias of UCS-2BE. 186UCS-2 is already registered by IANA and others that way. 187 188=back 189 190=head1 Surrogate Pairs 191 192To say the least, surrogate pairs were the biggest mistake of the 193Unicode Consortium. But according to the late Douglas Adams in I<The 194Hitchhiker's Guide to the Galaxy> Trilogy, C<In the beginning the 195Universe was created. This has made a lot of people very angry and 196been widely regarded as a bad move>. Their mistake was not of this 197magnitude so let's forgive them. 198 199(I don't dare make any comparison with Unicode Consortium and the 200Vogons here ;) Or, comparing Encode to Babel Fish is completely 201appropriate -- if you can only stick this into your ear :) 202 203Surrogate pairs were born when the Unicode Consortium finally 204admitted that 16 bits were not big enough to hold all the world's 205character repertoires. But they already made UCS-2 16-bit. What 206do we do? 207 208Back then, the range 0xD800-0xDFFF was not allocated. Let's split 209that range in half and use the first half to represent the C<upper 210half of a character> and the second half to represent the C<lower 211half of a character>. That way, you can represent 1024 * 1024 = 2121048576 more characters. Now we can store character ranges up to 213\x{10ffff} even with 16-bit encodings. This pair of half-character is 214now called a I<surrogate pair> and UTF-16 is the name of the encoding 215that embraces them. 216 217Here is a formula to ensurrogate a Unicode character \x{10000} and 218above; 219 220 $hi = ($uni - 0x10000) / 0x400 + 0xD800; 221 $lo = ($uni - 0x10000) % 0x400 + 0xDC00; 222 223And to desurrogate; 224 225 $uni = 0x10000 + ($hi - 0xD800) * 0x400 + ($lo - 0xDC00); 226 227Note this move has made \x{D800}-\x{DFFF} into a forbidden zone but 228perl does not prohibit the use of characters within this range. To perl, 229every one of \x{0000_0000} up to \x{ffff_ffff} (*) is I<a character>. 230 231 (*) or \x{ffff_ffff_ffff_ffff} if your perl is compiled with 64-bit 232 integer support! 233 234=head1 SEE ALSO 235 236L<Encode>, L<Encode::Unicode::UTF7>, L<http://www.unicode.org/glossary/>, 237L<http://www.unicode.org/unicode/faq/utf_bom.html>, 238 239RFC 2781 L<http://rfc.net/rfc2781.html>, 240 241The whole Unicode standard L<http://www.unicode.org/unicode/uni2book/u2.html> 242 243Ch. 15, pp. 403 of C<Programming Perl (3rd Edition)> 244by Larry Wall, Tom Christiansen, Jon Orwant; 245O'Reilly & Associates; ISBN 0-596-00027-8 246 247=cut 248