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<concept xml:lang="en" id="GUID-95954813-A4BC-5557-9E42-EB1AB1A6F381"><title>Unicode support</title><prolog><metadata><keywords/></metadata></prolog><conbody><p>This section describes the Unicode support to the STDLIB. </p> <p>The Unicode changes for STDLIB are categorised into groups: </p> <ul><li id="GUID-BDAD96FD-2EF9-5284-A5FA-2D867003B600"><p>Impact on the existing "<codeph>char*</codeph> " interfaces. </p> </li> <li id="GUID-F7CCA015-3B25-553C-B0CD-834AEDACF340"><p>Addition of new "<codeph>wchar_t*</codeph> " functions which use Unicode directly. </p> </li> </ul> <section><title>Impact on existing interfaces</title> <p>Symbian platform is a Unicode-based operating system. Hence, all operating system services which use <i>text</i> require that text to be presented in the 16-bit Unicode character encoding known as UCS-2. For STDLIB on Symbian platform, this is most significant in dealing with the names of files and directories, all of which are now Unicode sequences. </p> <p>To minimise the impact of this change on existing <i>narrow</i> C code, the STDLIB has adopted the policy that all such names in <i>char*</i> interfaces will be interpreted using the UTF-8 standard for encoding Unicode strings as 8-byte sequences. UTF-8 is a <i>no surprises</i> encoding and matches the 7-bit ASCII encoding for character codes 0 to 127. Hence, the existing string handling code will work without modification. </p> </section> <section><title>New interfaces</title> <p>The <codeph>wchar_t</codeph> type is defined and ISO-C standard wide character constants are supported. The <codeph>wchar_t</codeph> definition chosen is unsigned short to match the use of UCS-2, and a range of relevant functions now have wide character analogues which use <codeph>wchar_t*</codeph> in place of <codeph>char*</codeph>, for example: </p> <codeblock id="GUID-6AEF4AFD-D78C-54B2-9CB5-D4A8A56ECB45" xml:space="preserve">FILE *    fopen( const char *_name, const char *_type );</codeblock> <codeblock id="GUID-025E581B-1D28-5AA6-9999-7A1C89280487" xml:space="preserve">FILE *    wfopen( const wchar_t *_name, const wchar_t *_type );</codeblock> <p>and </p> <codeblock id="GUID-CEECB833-4C5F-5708-BF3A-C68975A3C58F" xml:space="preserve">DIR * opendir( const char * );</codeblock> <codeblock id="GUID-4491BF3F-A755-5ED9-B633-3D6960C3D501" xml:space="preserve">WDIR *    wopendir( const wchar_t * );</codeblock> <p>When such a pair of functions exist, the <codeph>char*</codeph> interface is implemented by converting the UTF-8 parameters to Unicode and calling the matching <codeph>wchar_t*</codeph> interface. </p> <p>The <codeph>mbtowc</codeph> family of conversion functions is provided to convert between UTF8 and Unicode, but there is no additional support for locales or other forms of multibyte encoding; to convert from encodings such as Shift-JIS, programmers are recommended to use the CHARCONV conversion routines via C++ wrapper functions callable from C. </p> <p>There are no implementations of <codeph>wchar_t*</codeph> versions of STDIO functions such as <codeph>fputc</codeph>. </p> </section> </conbody></concept>