NAME
mbtowc —
converts a multibyte character to a
wide character
LIBRARY
library “libc”
SYNOPSIS
#include
<stdlib.h>
int
mbtowc(wchar_t
* restrict pwc, const
char * restrict s, size_t
n);
DESCRIPTION
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
library “libc” never changes the
internal state of
mbtowc(),
except for calling
setlocale(3) with changing the LC_CTYPE
category of the current locale. Such
setlocale(3) call causes the internal state of this function to be
indeterminate.
The behaviour of
mbtowc()
is affected by the LC_CTYPE category of the current
locale.
There are 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, the mbtowc() returns:
- 0
- s points to a nul byte (‘\0’).
- positive
- Number of bytes for the valid multibyte character pointed to by
s. There are no cases that the value returned is
greater than the value of the
MB_CUR_MAXmacro. - -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.
ERRORS
mbtowc() may cause an error in the
following case:
- [
EILSEQ] - s points to an invalid or incomplete multibyte character.
SEE ALSO
STANDARDS
The mbtowc() function conforms to
ANSI X3.159-1989 (“ANSI C89”).
The restrict qualifier is added at ISO/IEC 9899:1999
(“ISO C99”).