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 processed (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 undefined.

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, Copyright (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.opengroup.org/unix/online.html .