size_t wcsrtombs(char *dest, const wchar_t **src,
size_t len, mbstate_t *ps);
If dest is not a NULL pointer, the wcsrtombs() function converts 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 wcr-
tomb(dest, *src, ps), as long as this call succeeds, and then incre-
menting dest by the number of bytes written and *src by one. The con-
version 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. 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 null wide character (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 terminat-
ing null byte ('\0'), is returned.
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 length limit exists.
In both of the above cases, if ps is a NULL pointer, a static anonymous
state known only to the wcsrtombs() function is used instead.
The programmer must ensure that there is room for at least len bytes at
The wcsrtombs() 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 con-
verted, (size_t) -1 is returned, and errno set to EILSEQ.
The behavior of wcsrtombs() depends on the LC_CTYPE category of the
GNU 2011-10-16 WCSRTOMBS(3)
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