MBRTOWC(3) BSD Library Functions Manual MBRTOWC(3)
mbrtowc -- converts a multibyte character to a wide character (restartable)
Standard C Library (libc, -lc)
mbrtowc(wchar_t * restrict pwc, const char * restrict s, size_t n, mbstate_t * restrict ps);
The mbrtowc() usually converts the multibyte character pointed to by s to a wide character, and stores the wide character to the wchar_t
object pointed to by pwc if pwc is non-NULL and s points to a valid character. The conversion happens in accordance with, and changes the
conversion state described in the mbstate_t object pointed to by ps. This function may examine at most n bytes of the array beginning from
If s points to a valid character and the character corresponds to a nul wide character, then the mbrtowc() places the mbstate_t object
pointed to by ps to an initial conversion state.
Unlike mbtowc(3), the mbrtowc() may accept the byte sequence pointed to by s not forming a complete multibyte character but which may be part
of a valid character. In this case, this function will accept all such bytes and save them into the conversion state object pointed to by
ps. They will be used at subsequent calls of this function to restart the conversion suspended.
The behaviour of mbrtowc() is affected by the LC_CTYPE category of the current locale.
These are the special cases:
s == NULL mbrtowc() sets the conversion state object pointed to by ps to an initial state and always returns 0. Unlike mbtowc(3), the
value returned does not indicate whether the current encoding of the locale is state-dependent.
In this case, mbrtowc() ignores pwc and n, and is equivalent to the following call:
mbrtowc(NULL, "", 1, ps);
pwc == NULL The conversion from a multibyte character to a wide character has taken place and the conversion state may be affected, but the
resulting wide character is discarded.
ps == NULL mbrtowc() uses its own internal state object to keep the conversion state, instead of ps mentioned in this manual page.
Calling any other functions in Standard C Library (libc, -lc) never changes the internal state of mbrtowc(), which is initial-
ized at startup time of the program.
In the usual cases, mbrtowc() returns:
0 The next bytes pointed to by s form a nul character.
positive If s points to a valid character, mbrtowc() returns the number of bytes in the character.
(size_t)-2 s points to a byte sequence which possibly contains part of a valid multibyte character, but which is incomplete. When n is at
least MB_CUR_MAX, this case can only occur if the array pointed to by s contains a redundant shift sequence.
(size_t)-1 s points to an illegal byte sequence which does not form a valid multibyte character. In this case, mbrtowc() sets errno to
indicate the error.
mbrtowc() may cause an error in the following case:
[EILSEQ] s points to an invalid or incomplete multibyte character.
[EINVAL] ps points to an invalid or uninitialized mbstate_t object.
mbrlen(3), mbtowc(3), setlocale(3)
The mbrtowc() function conforms to ISO/IEC 9899/AMD1:1995 (``ISO C90, Amendment 1''). The restrict qualifier is added at ISO/IEC 9899:1999
February 4, 2002 BSD