std::codecvt::length, std::codecvt::do_length
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<tbody> </tbody> public: int length( stateT& state, const externT* from, const externT* from_end, std::size_t max ) const |
(1) | |
protected: int do_length( stateT& state, const externT* from, const externT* from_end, std::size_t max ) const |
(2) | |
1)
-,
do_length - .2)
externT [from, from_end), state , max internT externT, . state, do_in(state, from, from_end, from, to, to+max, to) [to, to+max).:
attempts to convert the
externT characters from the character array defined by [from, from_end), given initial conversion state state, to at most max internT characters, and returns the number of externT characters that such conversion would consume. Modifies state as if by executing do_in(state, from, from_end, from, to, to+max, to) for some imaginary [to, to+max) output buffer.std::codecvt<char, char, std::mbstate_t> std::min(max, from_end-from):
The non-converting specialization
std::codecvt<char, char, std::mbstate_t> returns std::min(max, from_end-from)#include <locale>
#include <string>
#include <iostream>
int main()
{
// narrow multibyte encoding
std::string s = "z\u00df\u6c34\U0001d10b"; // or u8"z"
// or "\x7a\xc3\x9f\xe6\xb0\xb4\xf0\x9d\x84\x8b";
std::mbstate_t mb = std::mbstate_t();
std::cout << "Only the first " <<
std::use_facet<std::codecvt<wchar_t, char, std::mbstate_t>>(
std::locale("en_US.utf8")
).length(mb, &s[0], &s[s.size()], 2)
<< " bytes out of " << s.size() << " would be consumed "
" to produce the first 2 characters\n";
}
:
Only the first 3 bytes out of 10 would be consumed to produce the first 2 characters
.
[virtual] |
externT internT, , (virtual protected -) |