std::wstring_convert<Codecvt,Elem,Wide_alloc,Byte_alloc>::from_bytes (3) - Linux Manuals

std::wstring_convert<Codecvt,Elem,Wide_alloc,Byte_alloc>::from_bytes: std::wstring_convert<Codecvt,Elem,Wide_alloc,Byte_alloc>::from_bytes


std::wstring_convert<Codecvt,Elem,Wide_alloc,Byte_alloc>::from_bytes - std::wstring_convert<Codecvt,Elem,Wide_alloc,Byte_alloc>::from_bytes


Defined in header <locale>
wide_string from_bytes( char byte ); (1)
wide_string from_bytes( const char* ptr ); (2)
wide_string from_bytes( const byte_string& str ); (3)
wide_string from_bytes( const char* first, const char* last); (4)

Performs multibyte to wide conversion, using the codecvt facet supplied at construction.
1) Converts byte as if it was a string of length 1 to wide_string
2) Converts the null-terminated multibyte character sequence beginning at the character pointed to by ptr to wide_string
3) Converts the narrow string str to wide_string.
4) Converts the narrow multibyte character sequence [first, last) to wide_string
In all cases, the conversion begins in initial shift state, unless non-initial starting state was provided to this wstring_convert constructor. The number of characters converted and the final value of the conversion state are remembered and can be accessed with state() and converted()

Return value

A wide_string object containing the results of multibyte to wide conversion. If the conversion failed and there was a user-supplied wide-error string provided to the constructor of this wstring_convert, returns that wide-error string.


If this wstring_convert object was constructed without a user-supplied wide-error string, throws std::range_error on conversion failure.


// Run this code

  #include <iostream>
  #include <string>
  #include <locale>
  #include <codecvt>

  int main()
      std::string utf8 = u8"z\u00df\u6c34\U0001d10b"; // or u8"zß水𝄋"
                          // or "\x7a\xc3\x9f\xe6\xb0\xb4\xf0\x9d\x84\x8b";

      // the UTF-8 / UTF-16 standard conversion facet
      std::u16string utf16 = std::wstring_convert<std::codecvt_utf8_utf16<char16_t>, char16_t>{}.from_bytes(;
      std::cout << "UTF16 conversion produced " << utf16.size() << " code units:\n";
      for (char16_t c : utf16)
          std::cout << std::hex << std::showbase << c << '\n';

      // the UTF-8 / UTF-32 standard conversion facet
      std::u32string utf32 = std::wstring_convert<std::codecvt_utf8<char32_t>, char32_t>{}.from_bytes(utf8);
      std::cout << "UTF32 conversion produced " << std::dec << utf32.size() << " code units:\n";
      for (char32_t c : utf32)
          std::cout << std::hex << std::showbase << c << '\n';


  UTF16 conversion produced 5 code units:
  UTF32 conversion produced 4 code units:

See also

          converts a wide string into a byte string
to_bytes (public member function)
          converts a narrow multibyte character string to wide string, given state
mbsrtowcs (function)

do_in converts a string from externT to internT, such as when reading from file
          (virtual protected member function of std::codecvt<InternT,ExternT,State>)