Suspected memory corruption in `vsencoding`

[nyurik]

I have been implementing a Rust wrapper for FastPFor, and I reliably see free(): invalid next size (fast) - when using vsencoding codec. All other codecs work fine. The repo is a bit difficult - as this is a Rust wrapper, but the test is trivial - encode/decode a sequence of [1, 2, 3, 4, 5] using a 10-integer arrays.

[lemire]

Please read my comment here:

https://github.com/fast-pack/FastPFor/blob/49d44d94773518ef26486f7a58f8da08e8a498bb/headers/vsencoding.h#L22-L36

If you somehow need this code fixed, then I invite a pull request. I barely understand the code, and I did not write it (I only patched a few obvious issues).