std::mbrtowc

 

C++

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External libraries

 

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Primitive numeric conversions

to_chars (C++17) to_chars_result (C++17) from_chars (C++17) from_chars_result (C++17) chars_format (C++17)

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text_encoding (C++26)

 

Null-terminated multibyte strings

Functions Wide/multibyte examination mblen mbrlen mbsinit Multibyte/wide conversions mbtowc mbstowcs btowc mbrtowc mbsrtowcs    wctomb wcstombs wctob wcrtomb wcsrtombs mbrtoc8 (C++20) mbrtoc16 (C++11) mbrtoc32 (C++11) c8rtomb (C++20) c16rtomb (C++11) c32rtomb (C++11)

Types

mbstate_t

Macros

MB_LEN_MAX MB_CUR_MAX __STDC_UTF_16__ __STDC_UTF_32__ (C++11)(C++11)

 

Defined in header <cwchar>
std::size_t mbrtowc(wchar_t* pwc,                      constchar* s,                      std::size_t n,                      std::mbstate_t* ps );

Converts a narrow multibyte character to a wide character.

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 the corresponding wide character and stores it in *pwc (if pwc is not null).

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

If the wide character produced is the null character, the conversion state stored in *ps is the initial shift state.

Parameters

pwc	-	pointer to the location where the resulting wide character 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 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 pwc 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>(-2) if the next n bytes constitute an incomplete, but so far valid, multibyte character. Nothing is written to *pwc.
• static_cast<std::size_t>(-1) if encoding error occurs. Nothing is written to *pwc, the value EILSEQ is stored in errno and the value of *ps is left unspecified.

Example

Run this code

#include <clocale>#include <cstring>#include <cwchar>#include <iostream>   void print_mb(constchar* ptr){std::mbstate_t state =std::mbstate_t();// initial stateconstchar* end = ptr +std::strlen(ptr);int len;wchar_t wc;while((len = std::mbrtowc(&wc, ptr, end-ptr, &state))>0){std::wcout<<"Next "<< len <<" bytes are the character "<< wc <<'\n'; ptr += len;}}   int main(){std::setlocale(LC_ALL, "en_US.utf8");// UTF-8 narrow multibyte encodingconstchar* str ="z\u00df\u6c34\U0001d10b";// or u8"zß水𝄋"// or "\x7a\xc3\x9f\xe6\xb0\xb4\xf0\x9d\x84\x8b"; print_mb(str);}

Output:

Next 1 bytes are the character z Next 2 bytes are the character ß Next 3 bytes are the character 水 Next 4 bytes are the character 𝄋

See also

mbtowc	converts the next multibyte character to wide character (function)
wcrtomb	converts a wide character to its multibyte representation, given state (function)
do_in [virtual]	converts a string from ExternT to InternT, such as when reading from file (virtual protected member function of std::codecvt<InternT,ExternT,StateT>)
C documentation for mbrtowc