NAME

mbrtoc16, mbrtoc32 — convert a character to a Unicode character code (restartable)

SYNOPSIS

#include <uchar.h>

size_t mbrtoc16(char16_t *restrict pc16, const char *restrict s,
       size_t n, mbstate_t *restrict ps);
size_t mbrtoc32(char32_t *restrict pc32, const char *restrict s,
       size_t n, mbstate_t *restrict ps);


DESCRIPTION

^[CX] 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.1-2024 defers to the ISO C standard.

If s is a null pointer, the mbrtoc16() function shall be equivalent to the call:

mbrtoc16(NULL, "", 1, ps)

In this case, the values of the parameters pc16 and n are ignored.

If s is not a null pointer, the mbrtoc16() function shall inspect at most n bytes beginning with the byte pointed to by s to determine the number of bytes needed to complete the next character (including any shift sequences). If the function determines that the next character is complete and valid, it shall determine the values of the corresponding wide characters and then, if pc16 is not a null pointer, shall store the value of the first (or only) such character in the object pointed to by pc16. Subsequent calls shall store successive wide characters without consuming any additional input until all the characters have been stored. If the corresponding wide character is the null wide character, the resulting state described shall be the initial conversion state.

If ps is a null pointer, the mbrtoc16() function shall use its own internal mbstate_t object, which shall be 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 behavior of this function is affected by the LC_CTYPE category of the current locale.

The mbrtoc16() function shall not change the setting of errno if successful.

The mbrtoc32() function shall behave the same way as mbrtoc16() except that the first parameter shall point to an object of type char32_t instead of char16_t. References to pc16 in the above description shall apply as if they were pc32 when they are being read as describing mbrtoc32().

If called with a null ps argument, the mbrtoc16() function need not be thread-safe; however, such calls shall avoid data races with calls to mbrtoc16() with a non-null argument and with calls to all other functions.

If called with a null ps argument, the mbrtoc32() function need not be thread-safe; however, such calls shall avoid data races with calls to mbrtoc32() with a non-null argument and with calls to all other functions.

The implementation shall behave as if no function defined in this volume of POSIX.1-2024 calls mbrtoc16() or mbrtoc32() with a null pointer for ps.

RETURN VALUE

These functions shall return the first of the following that applies:

0

If the next n or fewer bytes complete the character that corresponds to the null wide character (which is the value stored).

between 1 and n inclusive

If the next n or fewer bytes complete a valid character (which is the value stored); the value returned shall be the number of bytes that complete the character.

(size_t)-3

If the next character resulting from a previous call has been stored, in which case no bytes from the input shall be consumed by the call.

(size_t)-2

If the next n bytes contribute to an incomplete but potentially valid character, and all n bytes have been processed (no value is stored). When n has at least the value of the {MB_CUR_MAX} macro, this case can only occur if s points at a sequence of redundant shift sequences (for implementations with state-dependent encodings).

(size_t)-1

If an encoding error occurs, in which case the next n or fewer bytes do not contribute to a complete and valid character (no value is stored). In this case, [EILSEQ] shall be stored in errno and the conversion state is undefined.

ERRORS

These functions shall fail if:

[EILSEQ]

An invalid character sequence is detected. ^[CX]  In the POSIX locale an [EILSEQ] error cannot occur since all byte values are valid characters.

These functions may fail if:

[EINVAL]

^[CX] ps points to an object that contains an invalid conversion state.

EXAMPLES

None.

APPLICATION USAGE

None.

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

c16rtomb

XBD <uchar.h>

CHANGE HISTORY

First released in Issue 8. Included for alignment with the ISO/IEC 9899:2018 standard.