NAME
mbrtowc - convert a character to a wide-character code (restartable)
SYNOPSIS
#include <wchar.h>
size_t mbrtowc(wchar_t *restrict pwc, const char *restrict s,
size_t n, mbstate_t *restrict ps);
DESCRIPTION
If s is a null pointer, the mbrtowc() function shall be equivalent to
the call:
mbrtowc(NULL, "", 1, ps)
In this case, the values of the arguments pwc and n are ignored.
If s is not a null pointer, the mbrtowc() function shall inspect at
most n bytes beginning at the byte pointed to by s to determine the
number of bytes needed to complete the next character (including any
shift sequences). If the function determines that the next character is
completed, it shall determine the value of the corresponding wide
character and then, if pwc is not a null pointer, shall store that
value in the object pointed to by pwc. If the corresponding wide
character is the null wide character, the resulting state described
shall be the initial conversion state.
If ps is a null pointer, the mbrtowc() function shall use its own
internal mbstate_t object, which shall be 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 mbrtowc().
The behavior of this function is affected by the LC_CTYPE category of
the current locale.
RETURN VALUE
The mbrtowc() function shall return the first of the following that
applies:
0 If the next n or fewer bytes complete the character that
corresponds to the null wide character (which is the value
stored).
between 1 and n inclusive
If the next n or fewer bytes complete a valid character (which
is the value stored); the value returned shall be the number of
bytes that complete the character.
(size_t)-2
If the next n bytes contribute to an incomplete but potentially
valid character, and all n bytes have been processed (no value
is stored). When n has at least the value of the {MB_CUR_MAX}
macro, this case can only occur if s points at a sequence of
redundant shift sequences (for implementations with state-
dependent encodings).
(size_t)-1
If an encoding error occurs, in which case the next n or fewer
bytes do not contribute to a complete and valid character (no
value is stored). In this case, [EILSEQ] shall be stored in
errno and the conversion state is undefined.
ERRORS
The mbrtowc() 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.
EXAMPLES
None.
APPLICATION USAGE
None.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
mbsinit() , the Base Definitions volume of IEEE Std 1003.1-2001,
<wchar.h>
COPYRIGHT
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 .