mbtowc
Synopsis
#include <stdlib.h>
int mbtowc(wchar_t *restrict pwc, const char *restrict s, size_t n);
Status
Partially implemented
Conformance
IEEE Std 1003.1-2017
Description
If s is not a null pointer, mbtowc() shall determine the number of bytes that constitute the character pointed to
by s. It shall then determine the wide-character code for the value of type wchar_t that corresponds to that
character. (The value of the wide-character code corresponding to the null byte is 0.) If the character is valid
and pwc is not a null pointer, mbtowc() shall store the wide-character code in the object pointed to by pwc.
The behavior of this function is affected by the LC_CTYPE category of the current locale. For a state-dependent
encoding, this function is placed into its initial state by a call for which its character pointer argument, s, is
a null pointer.
Subsequent calls with s as other than a null pointer shall cause the internal state of the function to be altered
as necessary. A call with s as a null pointer shall cause this function to return a non-zero value if encodings
have state dependency, and 0 otherwise. If the implementation employs special bytes to change the shift state, these
bytes shall not produce separate wide-character codes, but shall be grouped with an adjacent character. Changing the
LC_CTYPE category causes the shift state of this function to be unspecified. At most n bytes of the array pointed
to by s shall be examined.
The implementation shall behave as if no function defined in this volume of POSIX.1-2017 calls mbtowc().
The mbtowc() function need not be thread-safe.
Return value
If s is a null pointer, mbtowc() shall return a non-zero or 0 value, if character encodings, respectively, do
or do not have state-dependent encodings. If s is not a null pointer, mbtowc() shall either return 0
(if s points to the null byte), or return the number of bytes that constitute the converted character
(if the next n or fewer bytes form a valid character), or return -1 and shall set errno to indicate
the error (if they do not form a valid character).
In no case shall the value returned be greater than n or the value of the MB_CUR_MAX macro.
Errors
The mbtowc() function shall fail if:
EILSEQ- An invalid character sequence is detected. In the POSIX locale anEILSEQerror cannot occur since all byte values are valid characters.
Tests
Untested
Known bugs
None