MBSRTOWCS(P) POSIX Programmer's Manual MBSRTOWCS(P)
mbsrtowcs - convert a character string to a wide-character string (restartable)
size_t mbsrtowcs(wchar_t *restrict dst, const char **restrict src,
size_t len, mbstate_t *restrict ps);
The mbsrtowcs() function shall convert a sequence of characters, beginning in the conver-
sion state described by the object pointed to by ps, from the array indirectly pointed to
by src into a sequence of corresponding wide characters. If dst is not a null pointer, the
converted characters shall be stored into the array pointed to by dst. Conversion contin-
ues up to and including a terminating null character, which shall also be stored. Conver-
sion shall stop early in either of the following cases:
* A sequence of bytes is encountered that does not form a valid character.
* len codes have been stored into the array pointed to by dst (and dst is not a null
Each conversion shall take place as if by a call to the mbrtowc() 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 character)
or the address just past the last character converted (if any). If conversion stopped due
to reaching a terminating null character, and if dst is not a null pointer, the resulting
state described shall be the initial conversion state.
If ps is a null pointer, the mbsrtowcs() 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 behaves as
if no function defined in this volume of IEEE Std 1003.1-2001 calls mbsrtowcs().
The behavior of this function shall be affected by the LC_CTYPE category of the current
If the input conversion encounters a sequence of bytes that do not form a valid character,
an encoding error occurs. In this case, the mbsrtowcs() function stores the value of the
macro [EILSEQ] in errno and shall return (size_t)-1; the conversion state is undefined.
Otherwise, it shall return the number of characters successfully converted, not including
the terminating null (if any).
The mbsrtowcs() function may fail if:
EINVAL ps points to an object that contains an invalid conversion state.
EILSEQ Invalid character sequence is detected.
The following sections are informative.
mbsinit() , mbrtowc() , 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 MBSRTOWCS(P)