| Localization library | |||||||||||||||||||||||||
| Regular expressions library(C++11) | |||||||||||||||||||||||||
| Formatting library(C++20) | |||||||||||||||||||||||||
| Null-terminated sequence utilities | |||||||||||||||||||||||||
| Byte strings | |||||||||||||||||||||||||
| Multibyte strings | |||||||||||||||||||||||||
| Wide strings | |||||||||||||||||||||||||
| Primitive numeric conversions | |||||||||||||||||||||||||
| |||||||||||||||||||||||||
| Text encoding identifications | |||||||||||||||||||||||||
| |||||||||||||||||||||||||
Defined in header <cwchar> | ||
std::size_t mbrlen(constchar* s,std::size_t n,std::mbstate_t* ps); | ||
Determines the size, in bytes, of the remainder of the multibyte character whose first byte is pointed to bys, given the current conversion stateps.
This function is equivalent to the callstd::mbrtowc(nullptr, s, n, ps? ps:&internal) for some hidden objectinternal of typestd::mbstate_t, except that the expressionps is evaluated only once.
Contents |
| s | - | pointer to an element of a multibyte character string |
| n | - | limit on the number of bytes in s that can be examined |
| ps | - | pointer to the variable holding the conversion state |
#include <clocale>#include <cwchar>#include <iostream>#include <string> int main(){// allow mbrlen() to work with UTF-8 multibyte encodingstd::setlocale(LC_ALL,"en_US.utf8"); // UTF-8 narrow multibyte encodingstd::string str="水";// or u8"\u6c34" or "\xe6\xb0\xb4"std::mbstate_t mb=std::mbstate_t(); // simple use: length of a complete multibyte characterconststd::size_t len= std::mbrlen(&str[0], str.size(),&mb);std::cout<<"The length of "<< str<<" is "<< len<<" bytes\n"; // advanced use: restarting in the middle of a multibyte characterconststd::size_t len1= std::mbrlen(&str[0],1,&mb);if(len1==std::size_t(-2))std::cout<<"The first 1 byte of "<< str<<" is an incomplete multibyte char (mbrlen returns -2)\n"; conststd::size_t len2= std::mbrlen(&str[1], str.size()-1,&mb);std::cout<<"The remaining "<< str.size()-1<<" bytes of "<< str<<" hold "<< len2<<" bytes of the multibyte character\n"; // error case:std::cout<<"Attempting to call mbrlen() in the middle of "<< str<<" while in initial shift state returns "<<(int)mbrlen(&str[1], str.size(),&mb)<<'\n';}
Output:
The length of 水 is 3 bytes.The first 1 byte of 水 is an incomplete multibyte char (mbrlen returns -2)The remaining 2 bytes of 水 hold 2 bytes of the multibyte characterAttempting to call mbrlen() in the middle of 水 while in initial shift state returns -1
| converts the next multibyte character to wide character, given state (function)[edit] | |
| returns the number of bytes in the next multibyte character (function)[edit] | |
[virtual] | calculates the length of theExternT string that would be consumed by conversion into givenInternT buffer(virtual protected member function of std::codecvt<InternT,ExternT,StateT>)[edit] |
C documentation formbrlen | |
