[bcantrill]

One point of clarification: the C version does not have (and never had) a hash table; the C version had a BST (an AVL tree). Moreover, the "Rust hash table implementation" is in fact still B-tree based; the hash table described in the post is a much more nuanced implementation detail. The hash table implementation has really nothing to do with the C/Rust delta -- which is entirely a BST/B-tree delta. As I described in the post, implementing a B-tree in C is arduous -- and implementing a B-tree in C as a library would be absolutely brutal (because a B-tree relies on moving data). As I said in the piece, the memory safety of Rust is very much affecting performance here: it allows for the much more efficient data structure implementation.

[arghwhat]

I wouldn't consider implementing a B-tree in C any more "arduous" than implementing any other notable container/algorithm in C, nor would making a library be "brutal" as moving data really isn't an issue. Libraries are available if you need them.

Quite frankly, writing the same in Rust seems far, far more "arduous", and you'd only realistically be writing something using BTreeMap because someone else did the work for you.

However, being right there in std makes use much easier than searching around for an equivalent library to pull into your C codebase. That's the benefit.

[bcantrill]

I don't often do this, but I'm sorry, you don't know what you're talking about. If you bother to try looking for B-tree libraries in C, you will quickly find that they are either (1) the equivalent of undergraduate projects that are not used in production systems or (2) woven pretty deeply into a database implementation. This is because the memory model of C makes a B-tree library nasty: it will either be low performance or a very complicated interface -- and it is because moving data is emphatically an issue.