From cppreference.com
intwctomb(char*s,wchar_twc);Converts a wide character wc to multibyte encoding and stores it (including any shift sequences) in the char array whose first element is pointed to by s. No more than MB_CUR_MAX characters are stored. The conversion is affected by the current locale's LC_CTYPE category.
If wc is the null character, the null byte is written to s, preceded by any shift sequences necessary to restore the initial shift state.
If s is a null pointer, resets the global conversion state and determines whether shift sequences are used.
Parameters
s - pointer to the character array for output wc - wide character to convert Return value
If s is not a null pointer, returns the number of bytes that are contained in the multibyte representation of wc or -1 if wc is not a valid character.
If s is a null pointer, resets its internal conversion state to represent the initial shift state and returns 0 if the current multibyte encoding is not state-dependent (does not use shift sequences) or a non-zero value if the current multibyte encoding is state-dependent (uses shift sequences).
Notes
Each call to wctomb updates the internal global conversion state (a static object of type
, only known to this function). If the multibyte encoding uses shift states, this function is not reentrant. In any case, multiple threads should not call wctomb without synchronization:
may be used instead.
Example
Run this code
#include<clocale>#include<cstdlib>#include<iomanip>#include<iostream>#include<string>voidprint_wide(conststd::wstring&wstr){boolshifts=std::wctomb(nullptr,0);// reset the conversion statestd::cout<<"shift sequences are "<<(shifts?"":"not")<<" used\n"<<std::uppercase<<std::setfill('0');for(constwchar_twc:wstr){std::stringmb(MB_CUR_MAX,'\0');constintret=std::wctomb(&mb[0],wc);constchar*s=ret>1?"s":"";std::cout<<"multibyte char '"<<mb<<"' is "<<ret<<" byte"<<s<<": ["<<std::hex;for(inti{0};i!=ret;++i){constintc=0xFF&mb[i];std::cout<<(i?" ":"")<<std::setw(2)<<c;}std::cout<<"]\n"<<std::dec;}}intmain(){std::setlocale(LC_ALL,"en_US.utf8");// UTF-8 narrow multibyte encodingstd::wstringwstr=L"z\u00df\u6c34\U0001d10b";// or L"zß水𝄋"print_wide(wstr);}Output:
shift sequences are not used multibyte char 'z' is 1 byte: [7A] multibyte char 'ß' is 2 bytes: [C3 9F] multibyte char '水' is 3 bytes: [E6 B0 B4] multibyte char '𝄋' is 4 bytes: [F0 9D 84 8B] See also
converts the next multibyte character to wide character
(function)
converts a wide character to its multibyte representation, given state
(function)
[virtual]
converts a string from InternT to ExternT, such as when writing to file
(virtual protected member function of std::codecvt<InternT,ExternT,StateT>)