count_ones() gives wrong result for BitSlice

[geq1t]

Using bitvec 0.10, counting 1 bits in a bit slice within a single storage unit returns the total number of bits within the slice, not the number of 1 bits. Interestingly, it does work across when operating across byte boundaries. The following program:

fn main()
{
    let bits: [u8; 2] = [0b00111100, 0b11001100];
    let bv: bitvec::BitVec = (&bits as &[u8]).into();

    // Here, count_ones() fails
    let bs = &bv[4..8];
    println!("{} {}", bs, bs.count_ones());

    // Here, it works
    let bs = &bv[6..10];
    println!("{} {}", bs, bs.count_ones());
}

returns the following output

[1100] 4
[00, 11] 2

[myrrlyn]

Hi! Thanks so much for your report. The bug here is pretty embarrassing in how it got overlooked. The diff here is just inserting the correct .filter call in the sole-element case; I'd managed to forget to do that in both count_ones and count_zeros, and never noticed.

I've published 0.10.1 to https://crates.io/crates/bitvec; you should be able to get the fix with a cargo update command.

[myrrlyn]

@geq1t, I've been looking through the git history of this bug and I want to take a minute to say how extremely thankful I am not only for opening this issue but for the information you provided. The test case you gave reproduced, and your sentence,

Interestingly, it does work across when operating across byte boundaries.

Told me exactly what the error was while I was reading the email, before I'd even opened my editor. This was a great report; thanks for using bitvec and I hope it's working well for you!

[geq1t]

Thanks for fixing this so quickly! I'm glad the bug report was useful. I'll give it a try again next week, but other duties call right now.