NAME¶

std::wstring_convert::from_bytes - std::wstring_convert::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 <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';
}

Output:¶

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¶

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 converts a string from ExternT to InternT, such as when reading from file
[virtual] (virtual protected member function of
std::codecvt<InternT,ExternT,StateT>)