foo.md

Overview

Idea is to extract different Strategy classes (e.g. OpenAddressStrategy, LinearSearchStrategy) for hash algorithms which we forward to in RubyHash.

Initial approach can be found here: https://github.com/ChrisBr/jruby/commits/performance/hash-extract-class-2

Problems

• A lot of changes, high probability that something break
• The Strategy classes are still highly coupled to the RubyHash class as we need to hand over a lot of attributes / variables:
  • flags to calculate the hash value (we could calc the hash in RubyHash and hand it over but then rehashing also needs to happen in RubyHash class?)
  • The methods in the Strategy classes need to be very granular and composed in RubyHash (e.g. check for existence and adding of a RubyString as we need to freeze the string if it doesn't exist (see op_asetForString) or check for iterating (checkIterating))
• Iterations over key/value pairs need to happen in the Strategy class to be fast, otherwise we need again a temp RubyHashEntry class to use in an iterator (see visitAll)
• RubyHash needs to know about about DELETED_BIN or EMPTY_BIN values to compose the methods
• We still need RubyHash to not break API (e.g. getEntry, EntryView)

Benefit

• Strategy classes are relatively simple to implement