wcsnrtombs - convert a wide character string to a multibyte string
size_t wcsnrtombs (char *dest, const wchar_t **src, size_t nwc,
size_t len, mbstate_t *ps);
The wcsnrtombs function is like the wcsrtombs function, except that the
number of wide characters to be converted, starting at *src, is limited
If dest is not a NULL pointer, the wcsnrtombs function converts at most
nwc wide characters from the wide-character string *src to a multibyte
string starting at dest. At most len bytes are written to dest. The
shift state *ps is updated. The conversion is effectively performed by
repeatedly calling wcrtomb(dest,*src,ps), as long as this call succeeds,
and then incrementing dest by the number of bytes written and
*src by one. The conversion can stop for three reasons:
1. A wide character has been encountered that can not be represented as
a multibyte sequence (according to the current locale). In this case
*src is left pointing to the invalid wide character, (size_t)(-1) is
returned, and errno is set to EILSEQ.
2. nwc wide characters have been converted without encountering a
L'\0', or the length limit forces a stop. In this case *src is left
pointing to the next wide character to be converted, and the number of
bytes written to dest is returned.
3. The wide-character string has been completely converted, including
the terminating L'\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 bytes written to dest, excluding the terminating '\0' byte, is
If dest is NULL, len is ignored, and the conversion proceeds as above,
except that the converted bytes are not written out to memory, and that
no destination length limit exists.
In both of the above cases, if ps is a NULL pointer, a static anonymous
state only known to the wcsnrtombs function is used instead.
The programmer must ensure that there is room for at least len bytes at
The wcsnrtombs function returns the number of bytes that make up the
converted part of multibyte sequence, not including the terminating
null byte. If a wide character was encountered which could not be converted,
(size_t)(-1) is returned, and errno set to EILSEQ.
This function is a GNU extension.
The behaviour of wcsnrtombs depends on the LC_CTYPE category of the
Passing NULL as ps is not multi-thread safe.
GNU 1999-07-25 WCSNRTOMBS(3)
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