Incorrect Output rfind()

[arshidkv12]

    let haystack_str = BStr::new("日本語テキストです。01234５６７８９。E");
    let pos = haystack_str.rfind("。");
    println!("{}", pos.unwrap());

Output: 50
Expected output: 20

How to fix it?

[lopopolo]

bstr the library universally operates in terms of byte offsets. if you'd like to count in terms of characters, use one of the iterators like ByteSlice::chars. Something like this:

let haystack_str = BStr::new("日本語テキストです。01234５６７８９。E");
let pos = haystack_str.rfind("。").unwrap();
let s = &haystack_str[..pos];
let char_pos = s.chars().count();

[BurntSushi]

You need to explain why you expect the output to be 20. Because 50 looks correct.

While in not certain, you'll probably want to read this thread carefully: BurntSushi/aho-corasick#72

[BurntSushi]

if you'd like to count in terms of characters

And to be clear here, you almost never want this. Almost never. OP, if you describe the higher level problem you're trying to solve, we can probably guide you in the right direction.

[arshidkv12]

https://github.com/php/php-src/blob/master/ext/mbstring/tests/mb_strrpos_basic.phpt

Please check it

$needle1 = base64_decode('44CC');
var_dump(mb_strrpos($string_mb, $needle1));```

Output: 
-- Multibyte string 1 --
int(20)

[arshidkv12]

bstr the library universally operates in terms of byte offsets. if you'd like to count in terms of characters, use one of the iterators like ByteSlice::chars. Something like this:

let haystack_str = BStr::new("日本語テキストです。01234５６７８９。E");
let pos = haystack_str.rfind("。").unwrap();
let s = &haystack_str[..pos];
let char_pos = s.chars().count();

I think it is working. :)

[BurntSushi]

Read the thread I linked. Different environments can return different offsets depending on how the string type is represented. Seriously, read the thread I linked. It should answer everything.

[arshidkv12]

Read the thread I linked. Different environments can return different offsets depending on how the string type is represented. Seriously, read the thread I linked. It should answer everything.

Thank you