mbsrtowcs - convert a multibyte string to a wide-character string
Standard C library (
libc,
-lc)
#include <wchar.h>
size_t mbsrtowcs(wchar_t dest[restrict .len], const char **restrict src,
size_t len, mbstate_t *restrict ps);
If
dest is not NULL, the
mbsrtowcs() function converts the
multibyte string
*src to a wide-character string starting at
dest. At most
len wide characters are written to
dest.
The shift state
*ps is updated. The conversion is effectively performed
by repeatedly calling
mbrtowc(dest, *src, n, ps) where
n is some
positive number, as long as this call succeeds, and then incrementing
dest by one and
*src by the number of bytes consumed. The
conversion can stop for three reasons:
- •
- An invalid multibyte sequence has been encountered. In this
case, *src is left pointing to the invalid multibyte sequence,
(size_t) -1 is returned, and errno is set to
EILSEQ.
- •
-
len non-L'\0' wide characters have been stored at
dest. In this case, *src is left pointing to the next
multibyte sequence to be converted, and the number of wide characters
written to dest is returned.
- •
- The multibyte string has been completely converted,
including the terminating null wide character ('\0'), which has the side
effect of bringing back *ps to the initial state. In this case,
*src is set to NULL, and the number of wide characters written to
dest, excluding the terminating null wide character, is
returned.
If
dest is NULL,
len is ignored, and the conversion proceeds as
above, except that the converted wide characters are not written out to
memory, and that no length limit exists.
In both of the above cases, if
ps is NULL, a static anonymous state known
only to the
mbsrtowcs() function is used instead.
The programmer must ensure that there is room for at least
len wide
characters at
dest.
The
mbsrtowcs() function returns the number of wide characters that make
up the converted part of the wide-character string, not including the
terminating null wide character. If an invalid multibyte sequence was
encountered,
(size_t) -1 is returned, and
errno set to
EILSEQ.
For an explanation of the terms used in this section, see
attributes(7).
Interface |
Attribute |
Value |
mbsrtowcs () |
Thread safety |
MT-Unsafe race:mbsrtowcs/!ps |
POSIX.1-2001, POSIX.1-2008, C99.
The behavior of
mbsrtowcs() depends on the
LC_CTYPE category of
the current locale.
Passing NULL as
ps is not multithread safe.
iconv(3),
mbrtowc(3),
mbsinit(3),
mbsnrtowcs(3),
mbstowcs(3)