generic-cache-lookup

gistfile1.txt

;; The cache is a perfect hash table represented as a vector containing
;; cache entries. A cache entry is an inverted arg type id improper list
;; terminating to the the method procedure.
;; This allows for lock-free allocation-free recursive lookup
;; and reasonably fast dispatch

(def (generic-cache-lookup cache args)
  (def (lookup hash rest)
    (match rest
      ([arg . rest]
       (let* ((tid (generic-type-id arg))
              (hash (##fxxor hash (##symbol-hash tid))))
         (match (lookup hash rest)
           ([xtid . xrest]
            (and (##eq? tid xtid)
                 xrest))
           (else #f))))
      (else
       (let* ((len (##vector-length cache))
              (ix (##fxmodulo hash len)))
         (##vector-ref cache ix)))))

  (let (proc (lookup 0 args))
    (and (##procedure? proc) proc)))