# phpman > perldoc > Unicode::String ## NAME [Unicode::String](https://www.chedong.com/phpMan.php/perldoc/Unicode%3A%3AString/markdown) - String of Unicode characters (UTF-16BE) ## SYNOPSIS use [Unicode::String](https://www.chedong.com/phpMan.php/perldoc/Unicode%3A%3AString/markdown) qw(utf8 latin1 utf16be); $u = utf8("string"); $u = latin1("string"); $u = utf16be("\0s\0t\0r\0i\0n\0g"); print $u->utf32be; # 4 byte characters print $u->utf16le; # 2 byte characters + surrogates print $u->utf8; # 1-4 byte characters ## DESCRIPTION A "[Unicode::String](https://www.chedong.com/phpMan.php/perldoc/Unicode%3A%3AString/markdown)" object represents a sequence of Unicode characters. Methods are provided to convert between various external formats (encodings) and "[Unicode::String](https://www.chedong.com/phpMan.php/perldoc/Unicode%3A%3AString/markdown)" objects, and methods are provided for common string manipulations. The functions utf32be(), utf32le(), utf16be(), utf16le(), utf8(), utf7(), latin1(), uhex(), ### uchr initializing strings of the corresponding encoding. The "[Unicode::String](https://www.chedong.com/phpMan.php/perldoc/Unicode%3A%3AString/markdown)" objects overload various operators, which means that they in most cases can be treated like plain strings. Internally a "[Unicode::String](https://www.chedong.com/phpMan.php/perldoc/Unicode%3A%3AString/markdown)" object is represented by a string of 2 byte numbers in network byte order (big-endian). This representation is not visible by the API provided, but it might be useful to know in order to predict the efficiency of the provided methods. METHODS ### Class methods The following class methods are available: [Unicode::String](https://www.chedong.com/phpMan.php/perldoc/Unicode%3A%3AString/markdown)->stringify_as [Unicode::String](https://www.chedong.com/phpMan.php/perldoc/Unicode%3A%3AString/markdown)->stringify_as( $enc ) This method is used to specify which encoding will be used when "[Unicode::String](https://www.chedong.com/phpMan.php/perldoc/Unicode%3A%3AString/markdown)" objects are implicitly converted to and from plain strings. If an argument is provided it sets the current encoding. The argument should have one of the following: "ucs4", "utf32", "utf32be", "utf32le", "ucs2", "utf16", "utf16be", "utf16le", "utf8", "utf7", "latin1" or "hex". The default is "utf8". The stringify_as() method returns a reference to the current encoding function. $us = [Unicode::String](https://www.chedong.com/phpMan.php/perldoc/Unicode%3A%3AString/markdown)->new $us = [Unicode::String](https://www.chedong.com/phpMan.php/perldoc/Unicode%3A%3AString/markdown)->new( $initial_value ) This is the object constructor. Without argument, it creates an empty "[Unicode::String](https://www.chedong.com/phpMan.php/perldoc/Unicode%3A%3AString/markdown)" object. If an $initial_value argument is given, it is decoded according to the specified stringify_as() encoding, UTF-8 by default. In general it is recommended to import and use one of the encoding specific constructor functions instead of invoking this method. ### Encoding methods þÿ These methods get or set the value of the "Unicode::String" object by passing strings in the corresponding encoding. If a new value is passed as argument it will set the value of the "Unicode::String", and the previous value is returned. If no argument is passed then the current value is returned. To illustrate the encodings we show how the 2 character sample strin of "µm" (micro meter) is encoded for each one. =over =item $us->utf32be =item $us->utf32be( $newval The string passed should be in the UTF-32 encoding with bytes in big endian order. The sample "µm" is "\0\0\0\xB5\0\0\0m" in this encoding Alternative names for this method are utf32() and ucs4() =item $us->utf32le =item $us->utf32le( $newval The string passed should be in the UTF-32 encoding with bytes in littl endian order. The sample "µm" is is "\xB5\0\0\0m\0\0\0" in this encoding. =item $us->utf16be =item $us->utf16be( $newval The string passed should be in the UTF-16 encoding with bytes in big endian order. The sample "µm" is "\0\xB5\0m" in this encoding. Alternative names for this method are utf16() and ucs2() If the string passed to utf16be() starts with the Unicode byte order mark in little endian order, the result is as if utf16le() was calle instead. =item $us->utf16le =item $us->utf16le( $newval The string passed should be in the UTF-16 encoding with bytes in little endian order. The sample "µm" is is "\xB5\0m\0" in thi encoding. This is the encoding used by the Microsoft Windows API. If the string passed to utf16le() starts with the Unicode byte order mark in big endian order, the result is as if utf16le() was called instead. =item $us->utf =item $us->utf8( $newval The string passed should be in the UTF-8 encoding. The sample "µm" i "\xC2\xB5m" in this encoding =item $us->utf =item $us->utf7( $newval The string passed should be in the UTF-7 encoding. The sample "µm" i "+ALU-m" in this encoding. The UTF-7 encoding only use plain US-ASCII characters for th encoding. This makes it safe for transport through 8-bit strippin protocols. Characters outside the US-ASCII range are base64-encoded and '+' is used as an escape character. The UTF-7 encoding is described in RFC 1642. If the (global) variable $[Unicode::String::UTF7_OPTIONAL_DIRECT_CHAR](https://www.chedong.com/phpMan.php/perldoc/Unicode%3A%3AString%3A%3AUTF7OPTIONALDIRECTCHAR/markdown) is TRUE, then a wider range of characters are encoded as themselves. It is even TRUE by default. The characters affected by this are ! " # $ % & * ; < = > @ [ ] ^ _ ` { | } =item $us->latin =item $us->latin1( $newval The string passed should be in the ISO-8859-1 encoding. The sample "µm" is "\xB5m" in this encoding Characters outside the "\x00" .. "\xFF" range are simply removed fro the return value of the latin1() method. If you want more control over the mapping from Unicode to ISO-8859-1, use the C<[Unicode::Map8](https://www.chedong.com/phpMan.php/perldoc/Unicode%3A%3AMap8/markdown) class. This is also the way to deal with other 8-bit character sets =item $us->hex =item $us->hex( $newval The string passed should be plain ASCII where each Unicode character is represented by the "U+XXXX" string and separated by a single spac character. The "U+" prefix is optional when setting the value. The sample "µm" is "U+00b5 U+006d" in this encoding. =bac =head2 String Operations The following methods are available: =over =item $us->as_string Converts a C<[Unicode::String](https://www.chedong.com/phpMan.php/perldoc/Unicode%3A%3AString/markdown)> to a plain string according to the setting of stringify_as(). The default stringify_as() encoding is "utf8" =item $us->as_nu Converts a C<[Unicode::String](https://www.chedong.com/phpMan.php/perldoc/Unicode%3A%3AString/markdown)> to a number. Currently only the digit in the range 0x30 .. 0x39 are recognized. The plan is to eventually support all Unicode digit characters =item $us->as_bool Converts a C<[Unicode::String](https://www.chedong.com/phpMan.php/perldoc/Unicode%3A%3AString/markdown)> to a boolean value. Only the empt string is FALSE. A string consisting of only the character U+0030 i considered TRUE, even if Perl consider "0" to be FALSE =item $us->repeat( $count Returns a new C<[Unicode::String](https://www.chedong.com/phpMan.php/perldoc/Unicode%3A%3AString/markdown)> where the content of $us is repeate $count times. This operation is also overloaded as: $us x $count =item $us->concat( $other_string Concatenates the string $us and the string $other_string. I $other_string is not an C<[Unicode::String](https://www.chedong.com/phpMan.php/perldoc/Unicode%3A%3AString/markdown)> object, then it is firs passed to the [Unicode::String](https://www.chedong.com/phpMan.php/perldoc/Unicode%3A%3AString/markdown)->new constructor function. This operation is also overloaded as: $us . $other_strin =item $us->append( $other_string Appends the string $other_string to the value of $us. I $other_string is not an C<[Unicode::String](https://www.chedong.com/phpMan.php/perldoc/Unicode%3A%3AString/markdown)> object, then it is firs passed to the [Unicode::String](https://www.chedong.com/phpMan.php/perldoc/Unicode%3A%3AString/markdown)->new constructor function. This operation is also overloaded as: $us .= $other_string =item $us->cop Returns a copy of the current C<[Unicode::String](https://www.chedong.com/phpMan.php/perldoc/Unicode%3A%3AString/markdown)> object. This operation is overloaded as the assignment operator =item $us->lengt Returns the length of the C<[Unicode::String](https://www.chedong.com/phpMan.php/perldoc/Unicode%3A%3AString/markdown)>. Surrogate pairs are still counted as 2 =item $us->byteswa This method will swap the bytes in the internal representation of th C<[Unicode::String](https://www.chedong.com/phpMan.php/perldoc/Unicode%3A%3AString/markdown)> object. Unicode reserve the character U+FEFF character as a byte order mark. This works because the swapped character, U+FFFE, is reserved to not be valid. For strings that have the byte order mark as the firs character, we can guaranty to get the byte order right with th following code $ustr->byteswap if $ustr->ord == 0xFFFE =item $us->unpac Returns a list of integers each representing an UCS-2 character code =item $us->pack( @uchr Sets the value of $us as a sequence of UCS-2 characters with the characters codes given as parameter. =item $us->ord Returns the character code of the first character in $us. The ord() method deals with surrogate pairs, which gives us a result-range o 0x0 .. 0x10FFFF. If the $us string is empty, undef is returned. =item $us->chr( $code Sets the value of $us to be a string containing the character assigned code $code. The argument $code must be an integer in the range 0x .. 0x10FFFF. If the code is greater than 0xFFFF then a surrogate pair created. =item $us->nam In scalar context returns the official Unicode name of the first character in $us. In array context returns the name of all characters in $us. Also see L<[Unicode::CharName](https://www.chedong.com/phpMan.php/perldoc/Unicode%3A%3ACharName/markdown)> =item $us->substr( $offset =item $us->substr( $offset, $length =item $us->substr( $offset, $length, $subst Returns a sub-string of $us. Works similar to the builtin substr( function =item $us->index( $other =item $us->index( $other, $pos Locates the position of $other within $us, possibly starting the search at position $pos. =item $us->cho Chops off the last character of $us and returns it (as a C<[Unicode::String](https://www.chedong.com/phpMan.php/perldoc/Unicode%3A%3AString/markdown)> object) =bac =head1 FUNCTIONS The following functions are provided. None of these are exported by default =over =item byteswap2( $str, ... This function will swap 2 and 2 bytes in the strings passed as arguments. If this function is called in void context then it will modify its arguments in-place. Otherwise, the swappe strings are returned =item byteswap4( $str, ... The byteswap4 function works similar to byteswap2, but will revers the order of 4 and 4 bytes =item latin1( $str =item utf7( $str =item utf8( $str =item utf16le( $str =item utf16be( $str =item utf32le( $str =item utf32be( $str Constructor functions for the various Unicode encodings. These return new C<[Unicode::String](https://www.chedong.com/phpMan.php/perldoc/Unicode%3A%3AString/markdown)> objects. The provided argument should be encoded correspondingly. =item uhex( $str Constructs a new C<[Unicode::String](https://www.chedong.com/phpMan.php/perldoc/Unicode%3A%3AString/markdown)> object from a string of he values. See hex() method above for description of the format. =item uchar( $num Constructs a new one character C<[Unicode::String](https://www.chedong.com/phpMan.php/perldoc/Unicode%3A%3AString/markdown)> object from Unicode character code. This works similar to perl's builtin chr( function =bac =head1 SEE ALS L<[Unicode::CharName](https://www.chedong.com/phpMan.php/perldoc/Unicode%3A%3ACharName/markdown)> L<[Unicode::Map8](https://www.chedong.com/phpMan.php/perldoc/Unicode%3A%3AMap8/markdown)> L<> L =head1 COPYRIGHT Copyright 1997-2000,2005 Gisle Aas This library is free software; you can redistribute it and/o modify it under the same terms as Perl itself. =cut # Some old code that is not used any more (because the methods are # now implemented as XS) and which I did not want to throw away yet. sub ucs4_inper my $self = shift unless (ref $self) { my $u = new [Unicode::String](https://www.chedong.com/phpMan.php/perldoc/Unicode%3A%3AString/markdown) $u->ucs4($self) return $u my $old = pack("N*", $self->ord) if (@_) $$self = "" for (unpack("N*", shift)) { $self->append(uchr($_)) } $old sub utf8_inper my $self = shift unless (ref $self) { # act as ctor my $u = new [Unicode::String](https://www.chedong.com/phpMan.php/perldoc/Unicode%3A%3AString/markdown) $u->utf8($self) return $u my $old; if (defined($$self) && defined wantarray) # encode UTF- my $uc; for $uc (unpack("n*", $$self)) if ($uc < 0x80) { # 1 byte representatio $old .= chr($uc) } elsif ($uc < 0x800) { # 2 byte representatio $old .= chr(0xC0 | ($uc >> 6)) . chr(0x80 | ($uc & 0x3F)) } else # 3 byte representatio $old .= chr(0xE0 | ($uc >> 12)) chr(0x80 | (($uc >> 6) & 0x3F)) chr(0x80 | ($uc & 0x3F)); } } if (@_) if (defined $_[0]) $$self = "" my $bytes = shift $bytes =~ s/^[\200-\277]+//; # can't start with 10xxxxxx while (length $bytes) { if ($bytes =~ s/^([\000-\177]+)//) { $$self .= pack("n*", unpack("C*", $1)) } elsif ($bytes =~ s/^([\300-\337])([\200-\277])//) my($b1,$b2) = (ord($1), ord($2)) $$self .= pack("n", (($b1 & 0x1F) << 6) | ($b2 & 0x3F)); } elsif ($bytes =~ s/^([\340-\357])([\200-\277])([\200-\277])//) { my($b1,$b2,$b3) = (ord($1), ord($2), ord($3)); $$self .= pack("n", (($b1 & 0x0F) << 12) | (($b2 & 0x3F) << 6) | ($b3 & 0x3F)) } else { croak "Bad UTF-8 data" } } else $$self = undef; } $old sub latin1_inper my $self = shift unless (ref $self) { # act as ctor my $u = new [Unicode::String](https://www.chedong.com/phpMan.php/perldoc/Unicode%3A%3AString/markdown) $u->latin1($self) return $u my $old; # XXX: should really check that none of the chars > 25 $old = pack("C*", unpack("n*", $$self)) if defined $$self; if (@_) # set the value if (defined $_[0]) $$self = pack("n*", unpack("C*", $_[0])); } else $$self = undef; } $old