std::wstring_convert::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.

Exceptions

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

Example

Run this code

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

int main()
{
    std::string utf8 =  u8"z\u00df\u6c34\U0001d10b"; // or u8"z"
                        // 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 << "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';
}

Output:

UTF16 conversion produced 5 code units:
0x7a
0xdf
0x6c34
0xd834
0xdd0b
UTF32 conversion produced 4 code units:
0x7a
0xdf
0x6c34
0x1d10b

Language
Headers
Freestanding and hosted implementations
Named requirements
Language support library
Concepts library (C++20)
Diagnostics library
Utilities library
Strings library
Containers library
Algorithms library
Iterators library
Numerics library
Input/output library
Localizations library
Regular expressions library (C++11)
Atomic operations library (C++11)
Thread support library (C++11)
Filesystem library (C++17)
Technical Specifications

Member functions
wstring_convert::wstring_convert
wstring_convert::~wstring_convert
wstring_convert::from_bytes
wstring_convert::to_bytes
wstring_convert::converted
wstring_convert::state

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

std::wstring_convert::from_bytes

Return value

Exceptions

Example

See also