NAME
mbsrtowcs —
converts a multibyte character string
to a wide-character string (restartable)
LIBRARY
library “libc”
SYNOPSIS
#include
<wchar.h>
size_t
mbsrtowcs(wchar_t
* restrict pwcs, const
char ** restrict s,
size_t n,
mbstate_t * restrict
ps);
DESCRIPTION
Thembsrtowcs()
converts the multibyte character string indirectly pointed to by
s to the corresponding wide-character string, and stores
it in the array pointed to by pwcs. The conversion stops
due to the following reasons:
- The conversion reaches a nul byte. In this case, the nul byte is also converted.
- The
mbsrtowcs() has already stored n wide characters. - The conversion encounters an invalid character.
Each character will be converted as if mbrtowc(3) is continuously called.
After conversion, if pwcs is not a null pointer, the pointer object pointed to by s is a null pointer (if the conversion is stopped due to reaching a nul byte) or the first byte of the character just after the last character converted.
If pwcs is not a null
pointer and the conversion is stopped due to reaching a nul byte, the
mbsrtowcs()
places the state object pointed to by ps to an initial
state after the conversion has taken place.
The behaviour of
mbsrtowcs()
is affected by the LC_CTYPE category of the current
locale.
These are the special cases:
- s == NULL || *s == NULL
- Undefined (may cause the program to crash).
- pwcs == NULL
- The conversion has taken place, but the resulting wide-character string was discarded. In this case, the pointer object pointed to by s is not modified and n is ignored.
- ps == NULL
- The
mbsrtowcs() uses its own internal state object to keep the conversion state, instead of ps mentioned in this manual page.Calling any other functions in library “libc” never changes the internal state of
mbsrtowcs(), which is initialized at startup time of the program.
RETURN VALUES
mbsrtowcs() returns:
- 0 or positive
- The value returned is the number of elements stored in the array pointed
to by pwcs, except for a terminating nul wide
character (if any). If pwcs is not
NULLand the value returned is equal to n, the wide-character string pointed to by pwcs is not nul-terminated. If pwcs is a null pointer, the value returned is the number of elements to contain the whole string converted, except for a terminating nul wide character. - (size_t)-1
- The array indirectly pointed to by s contains a byte
sequence forming invalid character. In this case,
mbsrtowcs() sets errno to indicate the error.
ERRORS
mbsrtowcs() may cause an error in the
following case:
- [
EILSEQ] - The pointer pointed to by s points to an invalid or incomplete multibyte character.
- [
EINVAL] - ps points to an invalid or uninitialized mbstate_t object.
SEE ALSO
STANDARDS
The mbsrtowcs() function conforms to
ISO/IEC 9899/AMD1:1995 (“ISO C90, Amendment
1”). The restrict qualifier is added at
ISO/IEC 9899:1999
(“ISO C99”).