MBSRTOWCS(3)               POSIX Programmer's Manual              MBSRTOWCS(3)



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

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(3)
