Lets say I have a string:
char theString[] = "你们好āa";
Given that my encoding is utf-8, this string is 12 bytes long (the three hanzi characters are three bytes each, the latin character with the macron is two bytes, and the 'a' is one byte:
strlen(theString) == 12
How can I count the number of characters? How can i do the equivalent of subscripting so that:
theString[3] == "好"
How can I slice, and cat such strings?
One thing that's not clear from the above answers is why it's not simple. Each character is encoded in one way or another - it doesn't have to be UTF-8, for example - and each character may have multiple encodings, with varying ways to handle combining of accents, etc. The rules are really complicated, and vary by encoding (e.g., utf-8 vs. utf-16).
This question has enormous security concerns, so it is imperative that this be done correctly. Use an OS-supplied library or a well-known third-party library to manipulate unicode strings; don't roll your own.