I have a requirement wherein my C++ code needs to do case insensitive comparison without worrying about whether the string is encoded or not, or the type of encoding involved. The string could be an ASCII or a non-ASCII, I just need to store it as is and compare it with a second string without concerning if the right locale is set and so forth.
Use case: Suppose my application receives a string (let's say it's a file name) initially as "Zoë Saldaña.txt" and it stores it as is. Subsequently, it receives another string "zoë saLdañA.txt", and the comparison between this and the first string should result in a match, by using a few APIs. Same with file name "abc.txt" and "AbC.txt".
I read about IBM's ICU and how it uses UTF-16 encoding by default. I'm curious to know:
If ICU provides a means of solving my requirement by seamlessly handling the strings regardless of their encoding type?
If the answer to 1. is no, then, using ICU's APIs, is it safe to normalize all strings (both ASCII and non-ASCII) to UTF-16 and then do the case-insensitive comparison and other operations?
Are there alternatives that facilitate this?
I read this post, but it doesn't quite meet my requirements.
Thanks!
The requirement is impossible. Computers don't work with characters, they work with numbers. But "case insensitive" comparisons are operations which work on characters. Locales determine which numbers correspond to which characters, and are therefore indispensible.
The above isn't just true for all progamming langguages, it's even true for case-sensitive comparisons. The mapping from character to number isn't always unique. That means that comparing two numbers doesn't work. There could be a locale where character 42 is equivalent to character 43. In Unicode, it's even worse. There are number sequences which have different lengths and still are equivalent. (precomposed and decomposed characters in particular)