MirOS Manual: mbtowc(3)

MBTOWC(3)                  BSD Programmer's Manual                   MBTOWC(3)


     mbtowc - converts a multibyte character to a wide character


     #include <stdlib.h>

     mbtowc(wchar_t *pwc, const char *s, size_t n);


     The mbtowc() usually converts the multibyte character pointed to by s to
     a wide character, and stores it in the wchar_t object pointed to by pwc
     if pwc is non-null and s points to a valid character. This function may
     inspect at most n bytes of the array beginning from s.

     In state-dependent encodings, s may point to the special sequence bytes
     to change the shift-state. Although such sequence bytes correspond to no
     individual wide-character code, mbtowc() changes its own state by the se-
     quence bytes and treats them as if they are a part of the subsequence
     multibyte character.

     Unlike mbrtowc(3), the first n bytes pointed to by s need to form an en-
     tire multibyte character. Otherwise, this function causes an error.

     Calling any other functions in libc never change the internal state of
     the mbtowc(), except for calling setlocale(3) with the LC_CTYPE category
     changed to that of the current locale. Such setlocale(3) calls cause the
     internal state of this function to be indeterminate.

     The behaviour of mbtowc() is affected by the LC_CTYPE category of the
     current locale.

     These are the special cases:

     s == NULL     mbtowc() initializes its own internal state to an initial
                   state, and determines whether the current encoding is
                   state-dependent. This function returns 0 if the encoding is
                   state-independent, otherwise non-zero. In this case, pwc is
                   completely ignored.

     pwc == NULL   mbtowc() executes the conversion as if pwc is non-null, but
                   a result of the conversion is discarded.

     n == 0        In this case, the first n bytes of the array pointed to by
                   s never form a complete character. Thus, the mbtowc() al-
                   ways fails.


     Normally, mbtowc() returns:

     0             s points to a null byte ('\0').

     positive      Number of bytes for the valid multibyte character pointed
                   to by s. There are no cases where the value returned is
                   greater than the value of the MB_CUR_MAX macro.

     -1            s points to an invalid or an incomplete multibyte charac-
                   ter. The mbtowc() also sets errno to indicate the error.

     When s is equal to NULL, mbtowc() returns:

     0           The current encoding is state-independent.

     non-zero    The current encoding is state-dependent.


     mbtowc() may cause an error in the following cases:

     [EILSEQ]      s points to an invalid or incomplete multibyte character.


     mblen(3), mbrtowc(3), setlocale(3)


     The mbtowc() function conforms to ANSI X3.159-1989 ("ANSI C").

MirOS BSD #10-current          February 3, 2002                              1

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