trusty (3) mbrtowc.3posix.gz

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 .