AIX Version 4.3 Differences Guide

wctomb()
wcswidth()
Table 48. Internal Locale Methods Called for Each Locale
Convert wide character to multi-byte character. All of the provided
wctomb() methods convert a Unicode value to the appropriate
multi-byte string. There are three different methods provided to
optimize performance of this operation based on the nature of the
multi-byte codeset:
• __wctomb_iso1() - Since ISO8859-1 is a proper subset of Unicode,
its data can be converted from Unicode by simply casting its 16-bit
value to an 8-bit value. This is the fastest method for converting
Unicode to ISO8859-1.
• __wctomb_utf() - UTF-8-based data can be converted from
Unicode by using a simple bit-shifting algorithm. This method
should be used for all UTF-8-based locales since it is faster than
the __wctomb_std() method listed below.
• __wctomb_std() - For all other codesets, the __wctomb_std()
method converts the multi-byte data from Unicode using the iconv()
interface. The conversion descriptor is defined as a static pointer so
that multiple calls to __wctomb_std() will not occur. Because this
locale method is dependent on libiconv, it has been placed into a
common locale method object in /usr/lib/nls/loc/methods/stdmeth.o
instead of the libc library to avoid creating an unnecessary
dependency between libc and libiconv.
Determine the display width of a wide character string. There is one
standard locale method, __wcswidth_std(), that loops through the
wide character string calling wcwidth() to determine the display
width of each character.
wcwidth() Determine the display width of a wide character. Since all wide
characters can be assumed to have the Unicode encoding, each
character's display width can be determined with a single locale
method.
• __wcwidth_std() - Determine the display width of a character based
on its Unicode value. Most characters that can be displayed have a
display width of 1; CJK ideographs and Hangul syllables will have a
display width of 2, and combining characters have a width of 0. The
assumption that the wide character encoding is Unicode allows for
a single wcwidth() method that is appropriate for all locales.
Localedef Command Impacts
The localedef command has a global method table that is defined
internally to the command and is used if the localedef command
user does not explicitly state the methods desired using the -m flag.
These tables will need to be modified and expanded to reflect the
newly-available methods.
Locale method Unicode locales ISO8859-1-based
locales
Single byte
non-ISO1-based
locales
Multi-byte locales
mblen() __mblen_utf() __mblen_sb() __mblen_sb() __mblen_std()
mbstopcs() __mbstopcs_std() __mbstopcs_std() __mbstopcs_std() __mbstopcs_std()
mbstowcs() __mbstowcs_std() __mbstowcs_std() __mbstowcs_std() __mbstowcs_std()
National Language Support 247