字符编码转换c++库

Introduction to libiconv

For historical reasons, international text is often encoded using a language or country dependent character encoding. With the advent of the internet and the frequent exchange of text across countries - even the viewing of a web page from a foreign country is a "text exchange" in this context -, conversions between these encodings have become important. They have also become a problem, because many characters which are present in one encoding are absent in many other encodings. To solve this mess, the Unicode encoding has been created. It is a super-encoding of all others and is therefore the default encoding for new text formats like XML.

Still, many computers still operate in locale with a traditional (limited) character encoding. Some programs, like mailers and web browsers, must be able to convert between a given text encoding and the user's encoding. Other programs internally store strings in Unicode, to facilitate internal processing, and need to convert between internal string representation (Unicode) and external string representation (a traditional encoding) when they are doing I/O. GNU libiconv is a conversion library for both kinds of applications.

Details

This library provides an iconv() implementation, for use on systems which don't have one, or whose implementation cannot convert from/to Unicode.

It provides support for the encodings:

European languages

ASCII, ISO-8859-{1,2,3,4,5,7,9,10,13,14,15,16}, KOI8-R, KOI8-U, KOI8-RU, CP{1250,1251,1252,1253,1254,1257}, CP{850,866,1131}, Mac{Roman,CentralEurope,Iceland,Croatian,Romania}, Mac{Cyrillic,Ukraine,Greek,Turkish}, Macintosh

Semitic languages

ISO-8859-{6,8}, CP{1255,1256}, CP862, Mac{Hebrew,Arabic}

Japanese

EUC-JP, SHIFT_JIS, CP932, ISO-2022-JP, ISO-2022-JP-2, ISO-2022-JP-1

Chinese

EUC-CN, HZ, GBK, CP936, GB18030, EUC-TW, BIG5, CP950, BIG5-HKSCS, BIG5-HKSCS:2004, BIG5-HKSCS:2001, BIG5-HKSCS:1999, ISO-2022-CN, ISO-2022-CN-EXT

Korean

EUC-KR, CP949, ISO-2022-KR, JOHAB

Armenian

ARMSCII-8

Georgian

Georgian-Academy, Georgian-PS

Tajik

KOI8-T

Kazakh

PT154, RK1048

Thai

ISO-8859-11, TIS-620, CP874, MacThai

Laotian

MuleLao-1, CP1133

Vietnamese

VISCII, TCVN, CP1258

Platform specifics

HP-ROMAN8, NEXTSTEP

Full Unicode

UTF-8 
UCS-2, UCS-2BE, UCS-2LE 
UCS-4, UCS-4BE, UCS-4LE 
UTF-16, UTF-16BE, UTF-16LE 
UTF-32, UTF-32BE, UTF-32LE 
UTF-7 
C99, JAVA

Full Unicode, in terms of uint16_t or uint32_t (with machine dependent endianness and alignment)

UCS-2-INTERNAL, UCS-4-INTERNAL

Locale dependent, in terms of `char' or `wchar_t' (with machine dependent endianness and alignment, and with OS and locale dependent semantics)

char, wchar_t 
The empty encoding name "" is equivalent to "char": it denotes the locale dependent character encoding.

When configured with the option --enable-extra-encodings, it also provides support for a few extra encodings:

European languages

CP{437,737,775,852,853,855,857,858,860,861,863,865,869,1125}

Semitic languages

CP864

Japanese

EUC-JISX0213, Shift_JISX0213, ISO-2022-JP-3

Chinese

BIG5-2003 (experimental)

Turkmen

TDS565

Platform specifics

ATARIST, RISCOS-LATIN1

It can convert from any of these encodings to any other, through Unicode conversion.

It has also some limited support for transliteration, i.e. when a character cannot be represented in the target character set, it can be approximated through one or several similarly looking characters. Transliteration is activated when "//TRANSLIT" is appended to the target encoding name.

libiconv is for you if your application needs to support multiple character encodings, but that support lacks from your system.

Installation

As usual for GNU packages:

$ ./configure --prefix=/usr/local$ make$ make install

After installing GNU libiconv for the first time, it is recommended to recompile and reinstall GNU gettext, so that it can take advantage of libiconv.

On systems other than GNU/Linux, the iconv program will be internationalized only if GNU gettext has been built and installed before GNU libiconv. This means that the first time GNU libiconv is installed, we have a circular dependency between the GNU libiconv and GNU gettext packages, which can be resolved by building and installing either

• first libiconv, then gettext, then libiconv again,

or (on systems supporting shared libraries, excluding AIX)

• first gettext, then libiconv, then gettext again.

Recall that before building a package for the second time, you need to erase the traces of the first build by running "make distclean".

This library can be built and installed in two variants:

• The library mode. This works on all systems, and uses a library libiconv.so and a header file <iconv.h>. (Both are installed through "make install".)

  To use it, simply #include <iconv.h> and use the functions.

  To use it in an autoconfiguring package:

  • If you don't use automake, append m4/iconv.m4 to your aclocal.m4 file.
  • If you do use automake, add m4/iconv.m4 to your m4 macro repository.
  • Add to the link command line of libraries and executables that use the functions the placeholder @LIBICONV@ (or, if using libtool for the link, @LTLIBICONV@). If you use automake, the right place for these additions are the *_LDADD variables.
  Note that iconv.m4 is also part of the GNU gettext package, which installs it in /usr/local/share/aclocal/iconv.m4.

• The libc plug/override mode. This works on GNU/Linux, Solaris and OSF/1 systems only. It is a way to get good iconv support without having glibc-2.1. It installs a librarypreloadable_libiconv.so. This library can be used with LD_PRELOAD, to override the iconv* functions present in the C library.
  • On GNU/Linux and Solaris:

    $ export LD_PRELOAD=/usr/local/lib/preloadable_libiconv.so

  • On OSF/1:

    $ export _RLD_LIST=/usr/local/lib/preloadable_libiconv.so:DEFAULT

  A program's source need not be modified, the program need not even be recompiled. Just set the LD_PRELOAD environment variable, that's it!

Copyright

The libiconv and libcharset libraries and their header files are under LGPL.

The iconv program is under GPL.

Downloading libiconv

libiconv can be found on in the subdirectory /pub/gnu/libiconv/ on your favorite GNU mirror. For other ways to obtain libiconv, please read How to get GNU Software.

The latest release is http://ftp.gnu.org/pub/gnu/libiconv/libiconv-1.14.tar.gz

The latest development sources can be obtained through the savannah project.

Documentation

Below are the links for the online documentation.

The iconv program

iconv.1.html

The library functions

iconv_open.3.html 
iconv.3.html 
iconv_close.3.html 
iconvctl.3.html 
iconv_open_into.3.html