mbrtowc(3p) — Linux manual page


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

PROLOG         top

       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         top

       mbrtowc — convert a character to a wide-character code

SYNOPSIS         top

       #include <wchar.h>

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

DESCRIPTION         top

       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.

       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 POSIX.1‐2017 calls mbrtowc().

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

       The mbrtowc() function need not be thread-safe if called with a
       NULL ps argument.

       The mbrtowc() function shall not change the setting of errno if

RETURN VALUE         top

       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         top

       The mbrtowc() function 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.

       The mbrtowc() function may fail if:

       EINVAL ps points to an object that contains an invalid conversion

       The following sections are informative.

EXAMPLES         top




RATIONALE         top




SEE ALSO         top

       mbsinit(3p), mbsrtowcs(3p)

       The Base Definitions volume of POSIX.1‐2017, wchar.h(0p)

COPYRIGHT         top

       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                       MBRTOWC(3P)

Pages that refer to this page: wchar.h(0p)fwprintf(3p)mbrlen(3p)mbsinit(3p)mbsrtowcs(3p)