std::codecvt_utf8_utf16
STD：：编解码器[医]UTF8[医]utf 16
| Defined in header | | |
|---|---|---|
| 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>; | | (since C++11) (deprecated in C++17) |
std::codecvt_utf8_utf16是std::codecvt方面，它封装了UTF-8编码字节字符串和UTF-16编码字符串之间的转换。如果Elem是一种32位类型，一个UTF-16码单元将存储在每个32位字符的输出序列中.
这是一个N：m转换面，不能与std::basic_filebuf%28，它只允许内部编码和外部编码之间的1：n转换，例如UTF-32/UTF-8。此方面可用于std::wstring_convert...
模板参数
| Elem | - | either char16_t, char32_t, or wchar_t |
|---|---|---|
| Maxcode | - | the largest value of Elem that this facet will read or write without error |
| Mode | - | a constant of type std::codecvt_mode |
成员函数
| (constructor) | constructs a new codecvt_utf8_utf16 facet (public member function) |
|---|---|
| (destructor) | destroys a codecvt_utf8_utf16 facet (public member function) |
STD：：编解码器[医]UTF8[医]utf 16：：codecvt[医]UTF8[医]utf 16
| explicit codecvt_utf8_utf16( std::size_t refs = 0 | | |
|---|
构造一个新的std::codecvt_utf8_utf16方面，传递初始参考计数器。refs给基类。
参数
| refs | - | the number of references that link to the facet |
|---|
STD：：编解码器[医]UTF8[医]utf 16：：~codecvt[医]UTF8[医]utf 16
| ~codecvt_utf8_utf16( | | |
|---|
摧毁了这个面。与地区管理的方面不同，这个方面%27 s析构函数是公共的。
继承自STD：：编解码器
成员类型
| Member type | Definition |
|---|---|
| intern_type | internT |
| extern_type | externT |
| state_type | stateT |
成员对象
| Member name | Type |
|---|---|
| id (static) | std::locale::id |
成员函数
| out | invokes do_out (public member function of std::codecvt) |
|---|---|
| in | invokes do_in (public member function of std::codecvt) |
| unshift | invokes do_unshift (public member function of std::codecvt) |
| encoding | invokes do_encoding (public member function of std::codecvt) |
| always_noconv | invokes do_always_noconv (public member function of std::codecvt) |
| length | invokes do_length (public member function of std::codecvt) |
| max_length | invokes do_max_length (public member function of std::codecvt) |
受保护成员函数
| do_out virtual | converts a string from internT to externT, such as when writing to file (virtual protected member function of std::codecvt) |
|---|---|
| do_in virtual | converts a string from externT to internT, such as when reading from file (virtual protected member function of std::codecvt) |
| do_unshift virtual | generates the termination character sequence of externT characters for incomplete conversion (virtual protected member function of std::codecvt) |
| do_encoding virtual | returns the number of externT characters necessary to produce one internT character, if constant (virtual protected member function of std::codecvt) |
| do_always_noconv virtual | tests if the facet encodes an identity conversion for all valid argument values (virtual protected member function of std::codecvt) |
| do_length virtual | calculates the length of the externT string that would be consumed by conversion into given internT buffer (virtual protected member function of std::codecvt) |
| do_max_length virtual | returns the maximum number of externT characters that could be converted into a single internT character (virtual protected member function of std::codecvt) |
继承自STD：：编解码器[医]底座
| Member type | Definition |
|---|---|
| enum result { ok, partial, error, noconv }; | Unscoped enumeration type |
| Enumeration constant | Definition |
|---|---|
| ok | conversion was completed with no error |
| partial | not all source characters were converted |
| error | encountered an invalid character |
| noconv | no conversion required, input and output types are the same |
例
二次
#include <iostream>
#include <string>
#include <codecvt>
#include <cassert>
#include <locale>
int main()
{
std::string u8 = u8"z\u00df\u6c34\U0001f34c";
std::u16string u16 = u"z\u00df\u6c34\U0001f34c";
// UTF-8 to UTF-16/char16_t
std::u16string u16_conv = std::wstring_convert<
std::codecvt_utf8_utf16<char16_t>, char16_t>{}.from_bytes(u8
assert(u16 == u16_conv
std::cout << "UTF-8 to UTF-16 conversion produced "
<< u16_conv.size() << " code units:\n";
for (char16_t c : u16_conv)
std::cout << std::hex << std::showbase << c << ' ';
// UTF-16/char16_t to UTF-8
std::string u8_conv = std::wstring_convert<
std::codecvt_utf8_utf16<char16_t>, char16_t>{}.to_bytes(u16
assert(u8 == u8_conv
std::cout << "\nUTF-16 to UTF-8 conversion produced "
<< std::dec << u8_conv.size() << " bytes:\n" << std::hex;
for (char c : u8_conv)
std::cout << +(unsigned char)c << ' ';
}
二次
产出：
二次
UTF-8 to UTF-16 conversion produced 5 code units:
0x7a 0xdf 0x6c34 0xd83c 0xdf4c
UTF-16 to UTF-8 conversion produced 10 bytes:
0x7a 0xc3 0x9f 0xe6 0xb0 0xb4 0xf0 0x9f 0x8d 0x8c
二次
另见
| Characterconversions | locale-defined multibyte(UTF-8, GB18030) | UTF-8 | UTF-16 |
|---|---|---|---|
| UTF-16 | mbrtoc16 / c16rtomb(with C11's DR488) | codecvt<char16_t, char, mbstate_t>codecvt_utf8_utf16<char16_t>codecvt_utf8_utf16<char32_t>codecvt_utf8_utf16<wchar_t> | N/A |
| UCS2 | c16rtomb(without C11's DR488) | codecvt_utf8<char16_t> codecvt_utf8<wchar_t>(Windows). | codecvt_utf16<char16_t> codecvt_utf16<wchar_t>(Windows). |
| UTF-32 | mbrtoc32 / c32rtomb. | codecvt<char32_t, char, mbstate_t> codecvt_utf8<char32_t> codecvt_utf8<wchar_t>(non-Windows). | codecvt_utf16<char32_t> codecvt_utf16<wchar_t>(non-Windows). |
| system wide:UTF-32(non-Windows)UCS2(Windows) | mbsrtowcs / wcsrtombs use_facet<codecvt <wchar_t, char, mbstate_t>>(locale). | No | No |
| codecvt | converts between character encodings, including UTF-8, UTF-16, UTF-32 (class template) |
|---|---|
| codecvt_mode (C++11)(deprecated in C++17) | tags to alter behavior of the standard codecvt facets (enum) |
| codecvt_utf8 (C++11)(deprecated in C++17) | converts between UTF-8 and UCS2/UCS4 (class template) |
| codecvt_utf16 (C++11)(deprecated in C++17) | converts between UTF-16 and UCS2/UCS4 (class template) |
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