MBRTOWC(3P) POSIX Programmer's Manual MBRTOWC(3P)PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the corresponding
Linux manual page for details of Linux behavior), or the interface may
not be implemented on Linux.
NAMEmbrtowc — 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
The functionality described on this reference page is aligned with the
ISO C standard. Any conflict between the requirements described here
and the ISO C standard is unintentional. This volume of POSIX.1‐2008
defers to the ISO C standard.
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 char‐
acter 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 con‐
version state of the associated character sequence. The implementation
shall behave as if no function defined in this volume of POSIX.1‐2008
calls mbrtowc().
The behavior of this function is affected by the LC_CTYPE category of
the current locale.
The mbrtowc() function need not be thread-safe if called with a NULL ps
argument.
The mbrtowc() function shall not change the setting of errno if suc‐
cessful.
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 poten‐
tially 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 implementa‐
tions 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 char‐
acter (no value is stored). In this case, [EILSEQ] shall be
stored in errno and the conversion state is undefined.
ERRORS
The mbrtowc() function shall fail if:
EILSEQ An invalid character sequence is detected.
The mbrtowc() function may fail if:
EINVAL ps points to an object that contains an invalid conversion
state.
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
None.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSOmbsinit(), mbsrtowcs()
The Base Definitions volume of POSIX.1‐2008, <wchar.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
cal and Electronics Engineers, Inc and The Open Group. (This is
POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the source
files to man page format. To report such errors, see https://www.ker‐
nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 MBRTOWC(3P)
