A simple LRU cache for Rust that only caches items it has seen at least once before. The size of its internal memory is adjustable.
I didn't want to use a fixed cache size when I expect that most data will not be fetched twice, and that most of the time the number of items benefit from caching will be small. Good use cases: parsing large data structures that frequently cross-reference the same data chunk, reading a set of dictionary-compressed files where there are several different but shared dictionary, reading many files that all refer to shared parser profiles (eg. color profiles in images), etc.
Sure, a fixed size cache that stores "seen once" items would also work, but the memory usage would be higher than really necessary. Hence, this crate.