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PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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MBSRTOWCS(3P) POSIX Programmer's Manual MBSRTOWCS(3P)
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.
mbsnrtowcs, mbsrtowcs — convert a character string to a wide-
character string (restartable)
#include <wchar.h>
size_t mbsnrtowcs(wchar_t *restrict dst, const char **restrict src,
size_t nmc, size_t len, mbstate_t *restrict ps);
size_t mbsrtowcs(wchar_t *restrict dst, const char **restrict src,
size_t len, mbstate_t *restrict ps);
For mbsrtowcs(): 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.1‐2017 defers to the ISO C
standard.
The mbsrtowcs() function shall convert a sequence of characters,
beginning in the conversion 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 continues up to and including a
terminating null character, which shall also be stored. Conversion
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 pointer).
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. 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 mbsnrtowcs() function shall be equivalent to the mbsrtowcs()
function, except that the conversion of characters indirectly
pointed to by src is limited to at most nmc bytes (the size of the
input buffer), and under conditions where mbsrtowcs() would assign
the address just past the last character converted (if any) to the
pointer object pointed to by src, mbsnrtowcs() shall instead
assign the address just past the last byte processed (if any) to
that pointer object. If the input buffer ends with an incomplete
character, it is unspecified whether conversion stops at the end
of the previous character (if any), or at the end of the input
buffer. In the latter case, a subsequent call to mbsnrtowcs() with
an input buffer that starts with the remainder of the incomplete
character shall correctly complete the conversion of that
character.
The behavior of these functions shall be affected by the LC_CTYPE
category of the current locale.
The implementation shall behave as if no function defined in this
volume of POSIX.1‐2017 calls these functions.
The mbsnrtowcs() and mbsrtowcs() functions need not be thread-safe
if called with a NULL ps argument.
The mbsrtowcs() function shall not change the setting of errno if
successful.
If the input conversion encounters a sequence of bytes that do not
form a valid character, an encoding error occurs. In this case,
these functions shall store the value of the macro [EILSEQ] in
errno and shall return (size_t)-1; the conversion state is
undefined. Otherwise, these functions shall return the number of
characters successfully converted, not including the terminating
null (if any).
These functions shall fail if:
EILSEQ An invalid character sequence is detected. In the POSIX
locale an [EILSEQ] error cannot occur since all byte values
are valid characters.
These functions may fail if:
EINVAL ps points to an object that contains an invalid conversion
state.
The following sections are informative.
None.
None.
None.
A future version may require that when the input buffer ends with
an incomplete character, conversion stops at the end of the input
buffer.
iconv(3p), mbrtowc(3p), mbsinit(3p)
The Base Definitions volume of POSIX.1‐2017, wchar.h(0p)
Portions of this text are reprinted and reproduced in electronic
form from IEEE Std 1003.1-2017, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The
Open Group Base Specifications Issue 7, 2018 Edition, Copyright
(C) 2018 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 .
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.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2017 MBSRTOWCS(3P)
Pages that refer to this page: wchar.h(0p), iconv(3p), mbrtowc(3p), mbsinit(3p)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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