std::wstring_convert::from_bytes (3) Linux Manual Page

NAME

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

SYNOPSIS

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"zß水\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 << "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

See also

to_bytes (public member function)

converts a wide string into a byte string

mbsrtowcs (function)

converts a narrow multibyte character string to wide string, given state

do_in (virtual protected member function of std::codecvt<InternT,ExternT,State>)

converts a string from externT to internT, such as when reading from file

Index