# std::mbrtoc8

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< cpp‎ | string‎ | multibyte

Defined in header `<cuchar>` |  |
std::size_t mbrtoc8( char8_t* pc8, const char* s, std::size_t n, std::mbstate_t* ps ); |  | (since C++20)

Converts a narrow multibyte character to UTF-8 encoding.

If s is not a null pointer, inspects at most n bytes of the multibyte character string, beginning with the byte pointed to by s to determine the number of bytes necessary to complete the next multibyte character (including any shift sequences). If the function determines that the next multibyte character in s is complete and valid, converts it to UTF-8 and stores the first UTF-8 code unit in *pc8 (if pc8 is not null).

If UTF-8 encoding of the multibyte character in *s consists of more than one UTF-8 code unit, then after the first call to this function, *ps is updated in such a way that the next call to `mbrtoc8` will write out the additional UTF-8 code units, without considering *s.

If s is a null pointer, the values of n and pc8 are ignored and the call is equivalent to std::mbrtoc8(nullptr, "", 1, ps).

If UTF-8 code unit produced is u8'\0', the conversion state *ps represents the initial shift state.

The multibyte encoding used by this function is specified by the currently active C locale.

### Parameters

pc8 | - | pointer to the location where the resulting UTF-8 code units will be written
s | - | pointer to the multibyte character string used as input
n | - | limit on the number of bytes in s that can be examined
ps | - | pointer to the conversion state object used when interpreting the multibyte string

### Return value

The first of the following that applies:

- ​0​ if the character converted from s (and stored in *pc8 if non-null) was the null character.
- the number of bytes [1...n] of the multibyte character successfully converted from s.
- static_cast<std::size_t>(-3) if the next UTF-8 code unit from a character whose encoding consists of multiple code units has now been written to *pc8. No bytes are processed from the input in this case.
- static_cast<std::size_t>(-2) if the next n bytes constitute an incomplete, but so far valid, multibyte character. Nothing is written to *pc8.
- static_cast<std::size_t>(-1) if encoding error occurs. Nothing is written to *pc8, the value EILSEQ is stored in errno and the value of *ps is unspecified.

### Example

| This section is incomplete Reason: no example

### See also

c8rtomb (C++20) | converts UTF-8 string to narrow multibyte encoding (function)

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