WCSRTOMBS(P) POSIX Programmer's Manual WCSRTOMBS(P)
wcsrtombs - convert a wide-character string to a character string (restartable)
size_t wcsrtombs(char *restrict dst, const wchar_t **restrict src,
size_t len, mbstate_t *restrict ps);
The wcsrtombs() function shall convert a sequence of wide characters from the array indi-
rectly 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 character
* 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() function.
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 char-
acter) 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. Other-
wise, the mbstate_t object pointed to by ps shall be used to completely describe the cur-
rent 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 func-
tions, 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
If conversion stops because a code is reached that does not correspond to a valid charac-
ter, 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 unde-
fined. Otherwise, it shall return the number of bytes in the resulting character sequence,
not including the terminating null (if any).
The wcsrtombs() function may fail if:
EINVAL ps points to an object that contains an invalid conversion state.
EILSEQ A wide-character code does not correspond to a valid character.
The following sections are informative.
mbsinit() , wcrtomb() , the Base Definitions volume of IEEE Std 1003.1-2001, <wchar.h>
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 orig-
inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 WCSRTOMBS(P)