mbrtowc - convert a multibyte sequence to a wide character
#include <wchar.h>
size_t mbrtowc(wchar_t *pwc, const char *s, size_t n, mbstate_t *ps);
The main case for this function is when
s is not NULL and
pwc is
not NULL. In this case, the
mbrtowc() function inspects at most
n bytes of the multibyte string starting at
s, extracts the next
complete multibyte character, converts it to a wide character and stores it at
*pwc. It updates the shift state
*ps. If the converted wide
character is not L'\0' (the null wide character), it returns the number of
bytes that were consumed from
s. If the converted wide character is
L'\0', it resets the shift state
*ps to the initial state and returns
0.
If the
n bytes starting at
s do not contain a complete multibyte
character,
mbrtowc() returns
(size_t) -2. This can happen
even if
n >=
MB_CUR_MAX, if the multibyte string contains
redundant shift sequences.
If the multibyte string starting at
s contains an invalid multibyte
sequence before the next complete character,
mbrtowc() returns
(size_t) -1 and sets
errno to
EILSEQ. In this
case, the effects on
*ps are undefined.
A different case is when
s is not NULL but
pwc is NULL. In this
case, the
mbrtowc() function behaves as above, except that it does not
store the converted wide character in memory.
A third case is when
s is NULL. In this case,
pwc and
n are
ignored. If the conversion state represented by
*ps denotes an
incomplete multibyte character conversion, the
mbrtowc() function
returns
(size_t) -1, sets
errno to
EILSEQ, and
leaves
*ps in an undefined state. Otherwise, the
mbrtowc()
function puts
*ps in the initial state and returns 0.
In all of the above cases, if
ps is NULL, a static anonymous state known
only to the
mbrtowc() function is used instead. Otherwise,
*ps
must be a valid
mbstate_t object. An
mbstate_t object
a
can be initialized to the initial state by zeroing it, for example using
memset(&a, 0, sizeof(a));
The
mbrtowc() function returns the number of bytes parsed from the
multibyte sequence starting at
s, if a non-L'\0' wide character was
recognized. It returns 0, if a L'\0' wide character was recognized. It returns
(size_t) -1 and sets
errno to
EILSEQ, if an
invalid multibyte sequence was encountered. It returns
(size_t) -2 if it couldn't parse a complete multibyte character,
meaning that
n should be increased.
For an explanation of the terms used in this section, see
attributes(7).
Interface |
Attribute |
Value |
mbrtowc () |
Thread safety |
MT-Unsafe race:mbrtowc/!ps |
POSIX.1-2001, POSIX.1-2008, C99.
The behavior of
mbrtowc() depends on the
LC_CTYPE category of the
current locale.
mbsinit(3),
mbsrtowcs(3)