MBRTOWC(3) BSD Library Functions Manual MBRTOWC(3)NAMEmbrtowc — converts a multibyte character to a wide character
(restartable)
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <wchar.h>
size_t
mbrtowc(wchar_t * restrict pwc, const char * restrict s, size_t n,
mbstate_t * restrict ps);
DESCRIPTION
The mbrtowc() usually converts the multibyte character pointed to by s to
a wide character, and stores the wide character to the wchar_t object
pointed to by pwc if pwc is non-NULL and s points to a valid character.
The conversion happens in accordance with, and changes the conversion
state described in the mbstate_t object pointed to by ps. This function
may examine at most n bytes of the array beginning from s.
If s points to a valid character and the character corresponds to a nul
wide character, then the mbrtowc() places the mbstate_t object pointed to
by ps to an initial conversion state.
Unlike mbtowc(3), the mbrtowc() may accept the byte sequence pointed to
by s not forming a complete multibyte character but which may be part of
a valid character. In this case, this function will accept all such
bytes and save them into the conversion state object pointed to by ps.
They will be used at subsequent calls of this function to restart the
conversion suspended.
The behaviour of mbrtowc() is affected by the LC_CTYPE category of the
current locale.
These are the special cases:
s == NULL mbrtowc() sets the conversion state object pointed to by ps
to an initial state and always returns 0. Unlike
mbtowc(3), the value returned does not indicate whether the
current encoding of the locale is state-dependent.
In this case, mbrtowc() ignores pwc and n, and is equiva‐
lent to the following call:
mbrtowc(NULL, "", 1, ps);
pwc == NULL The conversion from a multibyte character to a wide charac‐
ter has taken place and the conversion state may be
affected, but the resulting wide character is discarded.
ps == NULL mbrtowc() uses its own internal state object to keep the
conversion state, instead of ps mentioned in this manual
page.
Calling any other functions in Standard C Library (libc,
-lc) never changes the internal state of mbrtowc(), which
is initialized at startup time of the program.
RETURN VALUES
In the usual cases, mbrtowc() returns:
0 The next bytes pointed to by s form a nul character.
positive If s points to a valid character, mbrtowc() returns the
number of bytes in the character.
(size_t)-2 s points to a byte sequence which possibly contains part of
a valid multibyte character, but which is incomplete. When
n is at least MB_CUR_MAX, this case can only occur if the
array pointed to by s contains a redundant shift sequence.
(size_t)-1 s points to an illegal byte sequence which does not form a
valid multibyte character. In this case, mbrtowc() sets
errno to indicate the error.
ERRORSmbrtowc() may cause an error in the following case:
[EILSEQ] s points to an invalid or incomplete multibyte charac‐
ter.
[EINVAL] ps points to an invalid or uninitialized mbstate_t
object.
SEE ALSOmbrlen(3), mbtowc(3), setlocale(3)STANDARDS
The mbrtowc() function conforms to ISO/IEC 9899/AMD1:1995 (“ISO C90,
Amendment 1”). The restrict qualifier is added at ISO/IEC 9899:1999
(“ISO C99”).
BSD February 4, 2002 BSD
