PROLOG

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

NAME

       mbsnrtowcs, mbsrtowcs — convert a character string to a wide-character string (restartable)

SYNOPSIS

       #include <wchar.h>

       size_t mbsnrtowcs(wchar_t *restrict dst, const char **restrict src,
           size_t nmc, size_t len, mbstate_t *restrict ps);
       size_t mbsrtowcs(wchar_t *restrict dst, const char **restrict src,
           size_t len, mbstate_t *restrict ps);

DESCRIPTION

       For  mbsrtowcs():  The functionality described on this reference page is aligned with the ISO C standard.
       Any conflict between the requirements described here and the ISO C standard is unintentional. This volume
       of POSIX.1‐2017 defers to the ISO C standard.

       The mbsrtowcs() function shall convert a sequence  of  characters,  beginning  in  the  conversion  state
       described  by the object pointed to by ps, from the array indirectly pointed to by src into a sequence of
       corresponding wide characters. If dst is not a null pointer, the converted  characters  shall  be  stored
       into the array pointed to by dst.  Conversion continues up to and including a terminating null character,
       which shall also be stored. Conversion shall stop early in either of the following cases:

        *  A sequence of bytes is encountered that does not form a valid character.

        *  len codes have been stored into the array pointed to by dst (and dst is not a null pointer).

       Each conversion shall take place as if by a call to the mbrtowc() function.

       If  dst  is  not  a  null  pointer,  the pointer object pointed to by src shall be assigned either a null
       pointer (if conversion stopped due to reaching a terminating null character) or the address just past the
       last character converted (if any). If conversion stopped due to reaching a  terminating  null  character,
       and if dst is not a null pointer, the resulting state described shall be the initial conversion state.

       If  ps  is a null pointer, the mbsrtowcs() function shall use its own internal mbstate_t object, which is
       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 mbsnrtowcs() function shall be equivalent to the mbsrtowcs() function, except that the conversion  of
       characters  indirectly  pointed to by src is limited to at most nmc bytes (the size of the input buffer),
       and under conditions where mbsrtowcs() would assign the address just past the  last  character  converted
       (if any) to the pointer object pointed to by src, mbsnrtowcs() shall instead assign the address just past
       the  last  byte  processed  (if  any) to that pointer object. If the input buffer ends with an incomplete
       character, it is unspecified whether conversion stops at the end of the previous character (if  any),  or
       at  the  end  of  the  input  buffer. In the latter case, a subsequent call to mbsnrtowcs() with an input
       buffer that starts with the remainder of the incomplete character shall correctly complete the conversion
       of that character.

       The behavior of these functions shall be affected by the LC_CTYPE category of the current locale.

       The implementation shall behave as if no function defined in this  volume  of  POSIX.1‐2017  calls  these
       functions.

       The mbsnrtowcs() and mbsrtowcs() functions need not be thread-safe if called with a NULL ps argument.

       The mbsrtowcs() function shall not change the setting of errno if successful.

RETURN VALUE

       If  the  input  conversion encounters a sequence of bytes that do not form a valid character, an encoding
       error occurs. In this case, these functions shall store the value of the  macro  [EILSEQ]  in  errno  and
       shall  return (size_t)-1; the conversion state is undefined.  Otherwise, these functions shall return the
       number of characters successfully converted, not including the terminating null (if any).

ERRORS

       These functions shall fail if:

       EILSEQ An invalid character sequence is detected.  In the POSIX locale an  [EILSEQ]  error  cannot  occur
              since all byte values are valid characters.

       These functions may fail if:

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

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       None.

RATIONALE

       None.

FUTURE DIRECTIONS

       A  future  version  may  require that when the input buffer ends with an incomplete character, conversion
       stops at the end of the input buffer.

SEE ALSO

       iconv(), mbrtowc(), mbsinit()

       The Base Definitions volume of POSIX.1‐2017, <wchar.h>

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard
       for Information  Technology  --  Portable  Operating  System  Interface  (POSIX),  The  Open  Group  Base
       Specifications  Issue  7, 2018 Edition, Copyright (C) 2018 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 .

       Any  typographical  or formatting errors that appear in this page are most likely to have been introduced
       during  the  conversion  of  the  source  files  to  man  page  format.  To  report  such   errors,   see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                                   2017                                     MBSRTOWCS(3POSIX)