MBRTOWC(3P)                                         POSIX Programmer's Manual                                        MBRTOWC(3P)



PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (con-
       sult the corresponding Linux manual page for details of Linux behavior), or the  interface  may  not  be  implemented  on
       Linux.

NAME
       mbrtowc - convert a character to a wide-character code (restartable)

SYNOPSIS
       #include <wchar.h>

       size_t mbrtowc(wchar_t *restrict pwc, const char *restrict s,
              size_t n, mbstate_t *restrict ps);


DESCRIPTION
       If s is a null pointer, the mbrtowc() function shall be equivalent to the call:


              mbrtowc(NULL, "", 1, ps)

       In this case, the values of the arguments pwc and n are ignored.

       If s is not a null pointer, the mbrtowc() function shall inspect at most n bytes beginning at the byte pointed to by s to
       determine the number of bytes needed to complete the next character (including any  shift  sequences).  If  the  function
       determines  that  the  next  character is completed, it shall determine the value of the corresponding wide character and
       then, if pwc is not a null pointer, shall store that value in the object pointed to by pwc.  If  the  corresponding  wide
       character is the null wide character, the resulting state described shall be the initial conversion state.

       If  ps  is a null pointer, the mbrtowc() function shall use its own internal mbstate_t object, which shall be initialized
       at program start-up to the initial conversion state. Otherwise, the mbstate_t object pointed to by ps shall  be  used  to
       completely describe the current conversion state of the associated character sequence. The implementation shall behave as
       if no function defined in this volume of IEEE Std 1003.1-2001 calls mbrtowc().

       The behavior of this function is affected by the LC_CTYPE category of the current locale.

RETURN VALUE
       The mbrtowc() function shall return the first of the following that applies:

       0      If the next n or fewer bytes complete the character that corresponds to the null  wide  character  (which  is  the
              value stored).

       between 1 and n inclusive

              If  the  next n or fewer bytes complete a valid character (which is the value stored); the value returned shall be
              the number of bytes that complete the character.

       (size_t)-2
              If the next n bytes contribute to an incomplete but potentially valid character, and all n bytes  have  been  pro-
              cessed  (no value is stored). When n has at least the value of the {MB_CUR_MAX} macro, this case can only occur if
              s points at a sequence of redundant shift sequences (for implementations with state-dependent encodings).

       (size_t)-1
              If an encoding error occurs, in which case the next n or fewer bytes do not contribute to  a  complete  and  valid
              character  (no value is stored). In this case, [EILSEQ] shall be stored in errno and the conversion state is unde-
              fined.


ERRORS
       The mbrtowc() function may fail if:

       EINVAL ps points to an object that contains an invalid conversion state.

       EILSEQ Invalid character sequence is detected.


       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       None.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       mbsinit(), the Base Definitions volume of IEEE Std 1003.1-2001, <wchar.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003  Edition,  Standard  for
       Information  Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copy-
       right (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any
       discrepancy  between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group
       Standard  is  the  referee   document.   The   original   Standard   can   be   obtained   online   at   http://www.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                   MBRTOWC(3P)