The interface is specified in CDR 2: https://common-lisp.net/project/cdr/document/2/index.html
This is currently in version 1.4, with MAP-GENERIC-HASH and WITH-GENERIC-HASH-TABLE-ITERATOR added. Still no LOOP path, though. There is, however, a pair of functions for hash tables using vectors of strings as keys.
Generic hash table implementation. This implementation is in the public domain.
This package defines four generic functions and two normal functions. The non-generic function MAKE-GENERIC-HASH-TABLE is used for hash table creation.
(make-generic-hash-table (:test 'eql) (:size 17))
(register-test-designator nickname hash-fn equal-fn)
Register a new generic hash function with nickname as the relevant :test parameter.
The generic functions are:
(hashref key table &optional (default nil))
This function does essentially the same thing as GETHASH.
((setf hashref) value key table &optional ignore)
For (setf (hashref ...) ...)
(map-generic-hash fn table)
(hashrem key table)
These functions dispatch somewhat differently depending on if they're fed a generic hash table or a built-in hash table.