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std::wstring_convert::from_bytes(3) | C++ Standard Libary | std::wstring_convert::from_bytes(3) |
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 <iostream>
#include <string>
#include <locale>
#include <codecvt>
int main()
{
std::string utf8 = u8"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 << "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 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,State>)
2022.07.31 | http://cppreference.com |