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

Converts a byte sequence to a wide string using the facet pointed to by cvtptr .

Before the conversion begins, if * this was not constructed with constructor overload (3) , cvtstate will be set to its default value (the initial conversion state).

The number of input elements successfully converted will be stored in cvtcount .

Return value

If the conversion succeeds, returns the conversion result. Otherwise, if * this is constructed with constructor overload (4) , returns wide_err_string .

Exceptions

If the conversion fails and * this was not constructed with constructor overload (4) , throws std::range_error .

Example

#include <codecvt>
#include <cstdint>
#include <iostream>
#include <locale>
#include <string>
 
int main()
{
    std::string utf8 = "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(utf8.data());
    std::cout << "UTF-16 conversion produced " << utf16.size()
              << " code units: " << std::showbase;
    for (char16_t c : utf16)
        std::cout << std::hex << static_cast<std::uint16_t>(c) << ' ';
 
    // 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 << "\nUTF-32 conversion produced " << std::dec
              << utf32.size() << " code units: ";
    for (char32_t c : utf32)
        std::cout << std::hex << static_cast<std::uint32_t>(c) << ' ';
    std::cout << '\n';
}

UTF-16 conversion produced 5 code units: 0x7a 0xdf 0x6c34 0xd834 0xdd0b
UTF-32 conversion produced 4 code units: 0x7a 0xdf 0x6c34 0x1d10b

See also