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std::codecvt_utf8_utf16

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template< class Elem, unsigned long Maxcode = 0x10ffff, std::codecvt_mode Mode = (std::codecvt_mode)0 > class codecvt_utf8_utf16 : public std::codecvt<Elem, char, std::mbstate_t>;
std::codecvt_utf8_utf16 std::codecvt , UTF-8 UTF-16 Elem 32... - , UTF-16 32- . codecvt UTF-8 , , .
:
std::codecvt_utf8_utf16 is a std::codecvt facet which encapsulates conversion between a UTF-8 encoded byte string and UTF-16 encoded character string. If Elem is a 32-bit type, one UTF-16 codepoint will be stored in each 32-bit character of the output sequence. This codecvt facet can be used to read and write UTF-8 files, both text and binary.
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Elem
char16_t, char32_t, wchar_t
:
either char16_t, char32_t, or wchar_t
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Maxcode
Elem,
:
the largest value of Elem that this facet will read or write without error
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Mode
std::codecvt_mode
:
a constant of type std::codecvt_mode
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std::codecvt

Member types

intern_type internT
extern_type externT
state_type stateT

Member objects

:
Member name
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 Type
id () std::locale::id

Member functions
do_out
:
invokes do_out
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(public - std::codecvt) []
do_in
:
invokes do_in
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(public - std::codecvt) []
do_unshift
:
invokes do_unshift
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(public - std::codecvt) []
do_encoding
:
invokes do_encoding
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(public - std::codecvt) []
do_always_noconv
:
invokes do_always_noconv
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(public - std::codecvt) []
do_length
:
invokes do_length
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(public - std::codecvt) []
do_max_length
:
invokes do_max_length
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(public - std::codecvt) []

Protected member functions

[virtual]
internT externT, ,
:
converts a string from internT to externT, such as when writing to file
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(virtual protected std::codecvt -) []
[virtual]
externT internT, ,
:
converts a string from externT to internT, such as when reading from file
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(virtual protected std::codecvt -) []
[virtual]
externT
:
generates the termination character sequence of externT characters for incomplete conversion
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(virtual protected std::codecvt -) []
[virtual]
externT , internT ,
:
returns the number of externT characters necessary to produce one internT character, if constant
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(virtual protected std::codecvt -) []
[virtual]
,
:
tests if the facet encodes an identity conversion for all valid argument values
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(virtual protected std::codecvt -) []
[virtual]
externT , internT
:
calculates the length of the externT string that would be consumed by conversion into given internT buffer
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(virtual protected std::codecvt -) []
[virtual]
externT , internT
:
returns the maximum number of externT characters that could be converted into a single internT character
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(virtual protected std::codecvt -) []


std::codecvt_base

enum result { ok, partial, error, noconv };
:
Unscoped enumeration type
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:
Enumeration constant
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 Definition
ok
:
conversion was completed with no error
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partial
:
not all source characters were converted
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error
:
encountered an invalid character
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noconv
,
:
no conversion required, input and output types are the same
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UTF -8 UTF-16 32- wchar_t
:
The following example demonstrates reading a UTF-8 file into a UTF-16 string on a system with 32-bit wchar_t
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#include <fstream>
#include <iostream>
#include <string>
#include <locale>
#include <codecvt>
int main()
{
    std::ofstream("text.txt") << u8"z\u6c34\U0001d10b";

    std::wifstream file1("text.txt");
    file1.imbue(std::locale("en_US.UTF8"));
    std::cout << "Normal read from file (using default UTF-8/UTF-32 codecvt)\n";
    for(wchar_t c; file1 >> c; )
        std::cout << std::hex << std::showbase << c << '\n';

    std::wifstream file2("text.txt");
    file2.imbue(std::locale(file2.getloc(), new std::codecvt_utf8_utf16<wchar_t>));
    std::cout << "UTF-16 read from the same file (using codecvt_utf8_utf16)\n";
    for(wchar_t c; file2 >> c; )
        std::cout << std::hex << std::showbase << c << '\n';
}

: 

Normal read from file (using default UTF-8/UTF-32 codecvt)
0x7a
0x6c34
0x1d10b
UTF-16 read from the same file (using codecvt_utf8_utf16)
0x7a
0x6c34
0xd834
0xdd0b

.

Character
conversions 		narrow multibyte
(char) 		UTF-8
(char) 		UTF-16
(char16_t)
UTF-16 mbrtoc16 / c16rtomb codecvt<char16_t, char, mbstate_t>
codecvt_utf8_utf16<char16_t>
codecvt_utf8_utf16<char32_t>
codecvt_utf8_utf16<wchar_t> 		/
UCS2 codecvt_utf8<char16_t> codecvt_utf16<char16_t>
UTF-32/UCS4
(char32_t) 		mbrtoc32 / c32rtomb codecvt<char32_t, char, mbstate_t>
codecvt_utf8<char32_t> 		codecvt_utf16<char32_t>
UCS2/UCS4
(wchar_t) 		codecvt_utf8<wchar_t> codecvt_utf16<wchar_t>
wide
(wchar_t) 		codecvt<wchar_t, char, mbstate_t>
mbsrtowcs / wcsrtombs
, UTF-8, UTF-16, UTF-32
( ) []
(C++11)( C++17)
 codecvt
() []
(C++11)( C++17)
 UTF-8 UCS-2/UCS-4
( ) []
(C++11)( C++17)
 UTF-16 UCS-2/UCS-4
( ) []
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