MBTOWC(3) OpenBSD Programmer's Manual MBTOWC(3)NAMEmbtowc - converts a multibyte character to a wide character
SYNOPSIS
#include <stdlib.h>
int
mbtowc(wchar_t * restrict pwc, const char * restrict s, size_t n);
DESCRIPTION
The mbtowc() usually converts the multibyte character pointed to by s to
a wide character, and stores it in the wchar_t object pointed to by pwc
if pwc is non-null and s points to a valid character. This function may
inspect at most n bytes of the array beginning from s.
In state-dependent encodings, s may point to the special sequence bytes
to change the shift-state. Although such sequence bytes correspond to no
individual wide-character code, mbtowc() changes its own state by the
sequence bytes and treats them as if they are a part of the subsequence
multibyte character.
Unlike mbrtowc(3), the first n bytes pointed to by s need to form an
entire multibyte character. Otherwise, this function causes an error.
Calling any other functions in libc never change the internal state of
the mbtowc(), except for calling setlocale(3) with the LC_CTYPE category
changed to that of the current locale. Such setlocale(3) calls cause the
internal state of this function to be indeterminate.
The behaviour of mbtowc() is affected by the LC_CTYPE category of the
current locale.
These are the special cases:
s == NULL mbtowc() initializes its own internal state to an initial
state, and determines whether the current encoding is
state-dependent. This function returns 0 if the encoding
is state-independent, otherwise non-zero. In this case,
pwc is completely ignored.
pwc == NULL mbtowc() executes the conversion as if pwc is non-null, but
a result of the conversion is discarded.
n == 0 In this case, the first n bytes of the array pointed to by
s never form a complete character. Thus, the mbtowc()
always fails.
RETURN VALUES
Normally, mbtowc() returns:
0 s points to a null byte (`\0').
positive Number of bytes for the valid multibyte character pointed
to by s. There are no cases where the value returned is
greater than the value of the MB_CUR_MAX macro.
-1 s points to an invalid or an incomplete multibyte
character. The mbtowc() also sets errno to indicate the
error.
When s is equal to NULL, mbtowc() returns:
0 The current encoding is state-independent.
non-zero The current encoding is state-dependent.
ERRORSmbtowc() may cause an error in the following cases:
[EILSEQ] s points to an invalid or incomplete multibyte character.
SEE ALSOmblen(3), mbrtowc(3), setlocale(3)STANDARDS
The mbtowc() function conforms to ANSI X3.159-1989 (``ANSI C''). The
restrict qualifier is added at ISO/IEC 9899/1999 (``ISO C99'').
CAVEATS
On error, callers of mbtowc() cannot tell whether the multibyte character
was invalid or incomplete. To treat incomplete data differently from
invalid data the mbrtowc(3) function can be used instead.
OpenBSD 4.9 November 20, 2010 OpenBSD 4.9
