aeb9161e2c
With Rust 2018 Edition, the `mod std` trick to alias `core` names to `std` no longer works, so switch to just having the code use `core` explicitly. So instead, switch to just using `core::*` for things that in core. This is more consistent with other Rust no_std code. And it allows us to enable `no_std` mode unconditionally in the crates that support it, which makes testing a little easier. There actually three cases: - For things in std and also in core, like `cmp`: Just use them via `core::*`. - For things in std and also in alloc, like `Vec`: Import alloc as std, as use them from std. This allows them to work on both stable (which doesn't provide alloc, but we don't support no_std mode anyway) and nightly. - For HashMap and similar which are not in core or alloc, import them in the top-level lib.rs files from either std or the third-party hashmap_core crate, and then have the code use super::hashmap_core. Also, no_std support continues to be "best effort" at this time and not something most people need to be testing.
This crate contains array-based data structures used by the core Cranelift code generator which represent a set of small ordered sets or maps.
These are not general purpose data structures that are somehow magically faster that the
standard library's BTreeSet and BTreeMap types.
The tradeoffs are different:
- Keys and values are expected to be small and copyable. We optimize for 32-bit types.
- A comparator object is used to compare keys, allowing smaller "context free" keys.
- Empty trees have a very small 32-bit footprint.
- All the trees in a forest can be cleared in constant time.