MBRTOWC(3) BSD Programmer's Manual MBRTOWC(3)
mbrtowc - converts a multibyte character to a wide character (restart-
able)
#include <wchar.h>
size_t
mbrtowc(wchar_t *pwc, const char *s, size_t n, mbstate_t *ps);
The mbrtowc() usually converts the multibyte character pointed to by s to
a wide character, and stores the wide character in 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 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 s.
If s points to a valid character and the character corresponds to a null
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 conver-
sion suspended.
The behaviour of the 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 charac-
ter has taken place and the conversion state may be affect-
ed, but the resultant 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 libc never change the inter-
nal state of mbrtowc(), which is initialized at startup
time of the program.
In the usual cases, mbrtowc() returns:
0 The next bytes pointed to by s form a null character.
positive If s points to a valid character, mbrtowc() returns the
number of bytes in the character.
(size_t)-2 s points to the byte sequence which possibly contains part
of a valid multibyte character, but which is incomplete.
When n is at least MB_CUR_MAX only occurs 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.
The mbrtowc() may causes 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), optu8to16(3), setlocale(3)
The mbrtowc() function conforms to ISO/IEC 9899/AMD1:1995 ("ISO C90,
Amendment 1").
MirBSD #10-current February 9, 2014 1