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

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Technical specifications

Symbols index

External libraries

 

Localizations library

Locales and facets
Locales
has_facet use_facet	locale
Facet category base classes
ctype_base codecvt_base messages_base	time_base money_base
ctype facets
ctype ctype_byname ctype<char>	codecvt codecvt_byname
numeric facets
num_get num_put	numpunct numpunct_byname
collate facets
collate	collate_byname
time facets
time_get time_get_byname	time_put time_put_byname
monetary facets
money_get money_put	moneypunct moneypunct_byname
messages facets
messages	messages_byname
Character classification and conversion
Character classification
isspace isblank (C++11) iscntrl isupper islower isalpha	isdigit ispunct isxdigit isalnum isprint isgraph
Conversions
toupper tolower	wstring_convert (C++11/17*) wbuffer_convert (C++11/17*)
Code conversion facets
codecvt_utf8 (C++11/17*) codecvt_utf16 (C++11/17*)	codecvt_utf8_utf16 (C++11/17*) codecvt_mode (C++11/17*)
C locale
LC_ALLLC_COLLATELC_CTYPELC_MONETARYLC_NUMERICLC_TIME	setlocale localeconv lconv

 

std::wstring_convert

Member functions

wstring_convert::wstring_convert

wstring_convert::~wstring_convert

wstring_convert::from_bytes

wstring_convert::to_bytes

wstring_convert::converted

wstring_convert::state

 

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