The wcsrtombs() function shall convert a sequence of wide characters from
the array indirectly pointed to by src into a sequence of corresponding
characters, beginning in the conversion state described by the object pointed
to by ps. If dst is not a null pointer, the converted characters
shall then be stored into the array pointed to by dst. Conversion
continues up to and including a terminating null wide character, which shall
also be stored. Conversion shall stop earlier in the following cases:
When a code is reached that does not correspond to a valid
When the next character would exceed the limit of
len total bytes to be stored in the array pointed to by dst
(and dst is not a null pointer)
Each conversion shall take place as if by a call to the wcrtomb()
If dst is not a null pointer, the pointer object pointed to by src
shall be assigned either a null pointer (if conversion stopped due to reaching
a terminating null wide character) or the address just past the last wide
character converted (if any). If conversion stopped due to reaching a
terminating null wide character, the resulting state described shall be the
initial conversion state.
If ps is a null pointer, the wcsrtombs() function shall use its
own internal mbstate_t object, which is initialized at program start-up
to the initial conversion state. Otherwise, the mbstate_t object
pointed to by ps shall be used to completely describe the current
conversion state of the associated character sequence. The implementation
shall behave as if no function defined in this volume of
IEEE Std 1003.1-2001 calls wcsrtombs().
If the application uses any of the _POSIX_THREAD_SAFE_FUNCTIONS or
_POSIX_THREADS functions, the application shall ensure that the
wcsrtombs() function is called with a non-NULL ps argument.
The behavior of this function shall be affected by the LC_CTYPE category
of the current locale.
If conversion stops because a code is reached that does not correspond to a
valid character, an encoding error occurs. In this case, the
wcsrtombs() function shall store the value of the macro [EILSEQ] in
errno and return ( size_t)-1; the conversion state is undefined.
Otherwise, it shall return the number of bytes in the resulting character
sequence, not including the terminating null (if any).
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html