Nuke 7.3

This release introduces new DataCache type and features some other improvements in custom data caching.

• Add new DataCache type - a cache backed by a local storage with an LRU cleanup policy. This type is a reworked version of the experimental data cache which was added in Nuke 7.0. It's now much simpler and also faster. It allows for reading and writing in parallel, it has a simple consistent API, and I hope it's going to be a pleasure to use.

Migration note: The storage format - which is simply a bunch of files in a directory really - is backward compatible with the previous implementation. If you'd like the new cache to continue working with the same path, please create it with "com.github.kean.Nuke.DataCache" name and use the same filename generator that you were using before:

try? DataCache(name: "com.github.kean.Nuke.DataCache", filenameGenerator: filenameGenerator)

• #160 DataCache now has a default FilenameGenerator on Swift 4.2 which uses SHA1 hash function provided by CommonCrypto (CommonCrypto is not available on the previous versions of Swift).

• #171 Fix a regression introduced in version 7.1 where experimental DataCache would not perform LRU data sweeps.

• Update DataCaching protocol. To store data you now need to implement a synchronous method func cachedData(for key: String) -> Data?. This change was necessary to make the data cache fit nicely in ImagePipeline infrastructure where each stage is managed by a separate OperationQueue and each operation respects the priority of the image requests associated with it.

• Add dataCachingQueue parameter to ImagePipeline.Configuration. The default maxConcurrentOperationCount is 2.

• Improve internal Operation type performance.