arrayref

This is a very small rust module, which contains just two macros, for the taking of array references to slices of... sliceable things. These two macros (which are awkwardly named) should be perfectly safe, but this is my first time writing unsafe code, so I will greatly appreciate any code review.

If you are considering providing code review, but think it might be too time-consuming, please consider that this is only 21 lines of actual code, although I have another 80 or so lines of test code.

The basic idea is that when we know at compile time the size of a slice we want, we should be able to take an array reference instead of a slice, which then will allow us to statically guarantee that the input to functions is of the correct size (when it is statically known what the size should be.

The motivating example is in encryption code, in which we often deal with pointers to small chunks of bytes that are of fixed size (e.g. keys, nonces, hashes, or authentication blocks). It would be lovely to express these constraints in our function signatures, but that has the side effect of requiring a copy of the containing slice to be made, in the common case where the information was embedded in a larger &[u8].

For an example of how these macros can be used (albeit not a great example, as I haven't fully cleaned up this code), see my rust translation of tweetnacl.