c++ - Getting the actual length of a UTF-8 encoded std::string?

Question

my std::string is utf-8 encoded so obviously, str.length() returns the wrong result.

I found this information but I'm not sure how I can use it to do this:

The following byte sequences are used to represent a character. The sequence to be used depends on the UCS code number of the character:

   0x00000000 - 0x0000007F:
       0xxxxxxx

   0x00000080 - 0x000007FF:
       110xxxxx 10xxxxxx

   0x00000800 - 0x0000FFFF:
       1110xxxx 10xxxxxx 10xxxxxx

   0x00010000 - 0x001FFFFF:
       11110xxx 10xxxxxx 10xxxxxx 10xxxxxx

How can I find the actual length of a UTF-8 encoded std::string? Thanks

Answer 1

Count all first-bytes (the ones that don't match 10xxxxxx).

int len = 0;
while (*s) len += (*s++ & 0xc0) != 0x80;