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String(3) User Contributed Perl Documentation String(3)
NAME
Unicode::String - String of Unicode characters (UCS2/UTF16)
SYNOPSIS
use Unicode::String qw(utf8 latin1 utf16);
$u = utf8("The Unicode Standard is a fixed-width, uniform ");
$u .= utf8("encoding scheme for written characters and text");
# convert to various external formats
print $u->ucs4; # 4 byte characters
print $u->utf16; # 2 byte characters + surrogates
print $u->utf8; # 1-4 byte characters
print $u->utf7; # 7-bit clean format
print $u->latin1; # lossy
print $u->hex; # a hexadecimal string
# all these can be used to set string value or as constructor
$u->latin1(" vre eller ikke vre");
$u = utf16("\0\0 \0v\0\0r\0e");
# string operations
$u2 = $u->copy;
$u->append($u2);
$u->repeat(2);
$u->chop;
$u->length;
$u->index($other);
$u->index($other, $pos);
$u->substr($offset);
$u->substr($offset, $length);
$u->substr($offset, $length, $substitute);
# overloading
$u .= "more";
$u = $u x 100;
print "$u\n";
# string <--> array of numbers
@array = $u->unpack;
$u->pack(@array);
# misc
$u->ord;
$u = uchr($num);
DESCRIPTION
A Unicode::String object represents a sequence of Unicode characters. The Unicode Stan-
dard is a fixed-width, uniform encoding scheme for written characters and text. This
encoding treats alphabetic characters, ideographic characters, and symbols identically,
which means that they can be used in any mixture and with equal facility. Unicode is mod-
eled on the ASCII character set, but uses a 16-bit encoding to support full multilingual
text.
Internally a Unicode::String object is a string of 2 byte values in network byte order
(big-endian). The class provide various methods to convert from and to various external
formats, and all string manipulations are made on strings in this the internal 16-bit for-
mat.
The functions utf16(), utf8(), utf7(), ucs2(), ucs4(), latin1(), uchr() can be imported
from the Unicode::String module and will work as constructors initializing strings of the
corresponding encoding. The ucs2() and utf16() are really aliases for the same function.
The Unicode::String objects overload various operators, so they will normally work like
plain 8-bit strings in Perl. This includes conversions to strings, numbers and booleans
as well as assignment, concatenation and repetition.
METHODS
The following methods are available:
Unicode::String->stringify_as( [$enc] )
This class method specify which encoding will be used when Unicode::String objects are
implicitly converted to and from plain strings. It define which encoding to assume
for the argument of the Unicode::String constructor new(). Without an encoding argu-
ment, stringify_as() returns the current encoding ctor function. The encoding argu-
ment ($enc) is a string with one of the following values: "ucs4", "ucs2", "utf16",
"utf8", "utf7", "latin1", "hex". The default is "utf8".
$us = Unicode::String->new( [$initial_value] )
This is the customary object constructor. Without argument, it creates an empty Uni-
code::String object. If an $initial_value argument is given, it is decoded according
to the specified stringify_as() encoding and used to initialize the newly created
object.
Normally you create Unicode::String objects by importing some of the encoding methods
below as functions into your namespace and calling them with an appropriate encoded
argument.
$us->ucs4( [$newval] )
The UCS-4 encoding use 32 bits per character. The main benefit of this encoding is
that you don't have to deal with surrogate pairs. Encoded as a Perl string we use
4-bytes in network byte order for each character.
The ucs4() method always return the old value of $us and if given an argument decodes
the UCS-4 string and set this as the new value of $us. The characters in $newval must
be in the range 0x0 .. 0x10FFFF. Characters outside this range is ignored.
$us->ucs2( [$newval] )
$us->utf16( [$newval] )
The ucs2() and utf16() are really just different names for the same method. The UCS-2
encoding use 16 bits per character. The UTF-16 encoding is identical to UCS-2, but
includes the use of surrogate pairs. Surrogates make it possible to encode characters
in the range 0x010000 .. 0x10FFFF with the use of two consecutive 16-bit chars.
Encoded as a Perl string we use 2-bytes in network byte order for each character (or
surrogate code).
The ucs2() method always return the old value of $us and if given an argument set this
as the new value of $us.
$us->utf8( [$newval] )
The UTF-8 encoding use 8-bit for the encoding of characters in the range 0x0 .. 0x7F,
16-bit for the encoding of characters in the range 0x80 .. 0x7FF, 24-bit for the
encoding of characters in the range 0x800 .. 0xFFFF and 32-bit for characters in the
range 0x01000 .. 0x10FFFF. Americans like this encoding, because plain US-ASCII char-
acters are still US-ASCII. Another benefit is that the character '\0' only occurs as
the encoding of 0x0, thus the normal NUL-terminated strings (popular in the C program-
ming language) can still be used.
The utf8() method always return the old value of $us encoded using UTF-8 and if given
an argument decodes the UTF-8 string and set this as the new value of $us.
$us->utf7( [$newval] )
The UTF-7 encoding only use plain US-ASCII characters for the encoding. This makes it
safe for transport through 8-bit stripping protocols. Characters outside the US-ASCII
range are base64-encoded and '+' is used as an escape character. The UTF-7 encoding
is described in RFC1642.
The utf7() method always return the old value of $us encoded using UTF-7 and if given
an argument decodes the UTF-7 string and set this as the new value of $us.
If the (global) variable $Unicode::String::UTF7_OPTIONAL_DIRECT_CHARS is TRUE, then a
wider range of characters are encoded as themselves. It is even TRUE by default. The
characters affected by this are:
! " # $ % & * ; < = > @ [ ] ^ _ ` { | }
$us->latin1( [$newval] )
The first 256 codes of Unicode is identical to the ISO-8859-1 8-bit encoding, also
known as Latin-1. The latin1() method always return the old value of $us and if given
an argument set this as the new value of $us. Characters outside the 0x0 .. 0xFF
range are ignored when returning a Latin-1 string. If you want more control over the
mapping from Unicode to Latin-1, use the Unicode::Map8 class. This is also the way to
deal with other 8-bit character sets.
$us->hex( [$newval] )
This method() return a plain ASCII string where each Unicode character is represented
by the "U+XXXX" string and separated by a single space character. This format can
also be used to set the value of $us (in which case the "U+" is optional).
$us->as_string;
Converts a Unicode::String to a plain string according to the setting of
stringify_as(). The default stringify_as() method is "utf8".
$us->as_num;
Converts a Unicode::String to a number. Currently only the digits in the range 0x30
.. 0x39 are recognized. The plan is to eventually support all Unicode digit charac-
ters.
$us->as_bool;
Converts a Unicode::String to a boolean value. Only the empty string is FALSE. A
string consisting of only the character U+0030 is considered TRUE, even if Perl con-
sider "0" to be FALSE.
$us->repeat( $count );
Returns a new Unicode::String where the content of $us is repeated $count times. This
operation is also overloaded as:
$us x $count
$us->concat( $other_string );
Concatenates the string $us and the string $other_string. If $other_string is not an
Unicode::String object, then it is first passed to the Unicode::String->new construc-
tor function. This operation is also overloaded as:
$us . $other_string
$us->append( $other_string );
Appends the string $other_string to the value of $us. If $other_string is not an Uni-
code::String object, then it is first passed to the Unicode::String->new constructor
function. This operation is also overloaded as:
$us .= $other_string
$us->copy;
Returns a copy of the current Unicode::String object. This operation is overloaded as
the assignment operator.
$us->length;
Returns the length of the Unicode::String. Surrogate pairs are still counted as 2.
$us->byteswap;
This method will swap the bytes in the internal representation of the Unicode::String
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 first character, we can guaranty to get the byte order
right with the following code:
$ustr->byteswap if $ustr->ord == 0xFFFE;
$us->unpack;
Returns a list of integers each representing an UTF-16 character code.
$us->pack( @uchr );
Sets the value of $us as a sequence of UTF-16 characters with the characters codes
given as parameter.
$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 of 0x0 .. 0x10FFFF. If the $us string
is empty, undef is returned.
$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 0x0 .. 0x10FFFF. If the code is
greater than 0xFFFF then a surrogate pair created.
$us->name
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 Unicode::CharName.
$us->substr( $offset, [$length, [$subst]] )
Returns a sub-string of $us. Works similar to the builtin substr function, but
because we can't make LVALUE subs yet, you have to pass the string you want to assign
to the sub-string as the 3rd parameter.
$us->index( $other, [$pos] );
Locates the position of $other within $us, possibly starting the search at position
$pos.
$us->chop;
Chops off the last character of $us and returns it (as a Unicode::String object).
FUNCTIONS
The following utility functions are provided. They will be exported on request.
byteswap2($str, ...)
This function will swap 2 and 2 bytes in the strings passed as arguments. This can be
used to fix up UTF-16 or UCS-2 strings from litle-endian systems. If this function is
called in void context, then it will modify its arguments in-place. Otherwise, then
swapped strings are returned.
byteswap4($str, ...)
The byteswap4 function works similar to byteswap2, but will reverse the order of 4 and
4 bytes. Can be used to fix litle-endian UCS-4 strings.
SEE ALSO
Unicode::CharName, Unicode::Map8, http://www.unicode.org/
COPYRIGHT
Copyright 1997-2000 Gisle Aas.
This library is free software; you can redistribute it and/or modify it under the same
terms as Perl itself.
perl v5.8.0 2003-03-10 String(3)
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On Apache/2.0.61 (Unix) PHP/4.4.7 mod_ssl/2.0.61 OpenSSL/0.9.7e mod_fastcgi/2.4.2 DAV/2 SVN/1.4.2
Under GNU General Public License
2009-01-06 21:13 @38.103.63.57 Crawled by CCBot/1.0 (+http://www.commoncrawl.org/bot.html)