std::mbrlen
Defined in header <cwchar>
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std::size_t mbrlen( const char* s, std::size_t n, std::mbstate_t* ps); |
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Determines the size, in bytes, of the remainder of the multibyte character whose first byte is pointed to by s
, given the current conversion state ps
.
This function is equivalent to the call std::mbrtowc(nullptr, s, n, ps?ps:&internal) for some hidden object internal
of type std::mbstate_t, except that the expression ps
is evaluated only once.
Parameters
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 |
Return value
0 if the next n
or fewer bytes complete the null character.
The number of bytes (between 1 and n) that complete a valid multibyte character
(size_t)-1 if encoding error occurs
(size_t)-2 if the next n
bytes are part of a possibly valid multibyte character, which is still incomplete after examining all n
bytes
Example
Run this code
#include <clocale> #include <string> #include <iostream> #include <cwchar> int main() { // allow mbrlen() to work with UTF-8 multibyte encoding std::setlocale(LC_ALL, "en_US.utf8"); // UTF-8 narrow multibyte encoding std::string str = u8"水"; // or u8"\u6c34" or "\xe6\xb0\xb4" std::mbstate_t mb = std::mbstate_t(); int len1 = std::mbrlen(&str[0], 1, &mb); if(len1 == -2) { std::cout << "The first 1 byte of " << str << " is an incomplete multibyte char (mbrlen returns -2)\n"; } int 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"; 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 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 character Attempting to call mbrlen() in the middle of 水 while in initial shift state returns -1
See also
converts the next multibyte character to wide character, given state (function) | |
returns the number of bytes in the next multibyte character (function) | |
[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<InternT,ExternT,State> ) |