(setf (getf (getf initargs 'plist) :slot-name-lists)
(list (list nil slot-name)))
initargs))
+\f
+;;;; FINDING SLOT DEFINITIONS
+;;;
+;;; Historical PCL found slot definitions by iterating over
+;;; CLASS-SLOTS, which is O(N) for number of slots, and moreover
+;;; requires a GF call (for SLOT-DEFINITION-NAME) for each slot in
+;;; list up to the desired one.
+;;;
+;;; Current SBCL hashes the effective slot definitions, and some
+;;; information pulled out from them into a simple-vector, with bucket
+;;; chains made out of plists keyed by the slot names. This fixes
+;;; gives O(1) performance, and avoid the GF calls.
+;;;
+;;; MAKE-SLOT-VECTOR constructs the hashed vector out of a list of
+;;; effective slot definitions and the class they pertain to, and
+;;; FIND-SLOT-DEFINITION knows how to look up slots in that vector.
+;;;
+;;; The only bit of cleverness in the implementation is to make the
+;;; vectors fairly tight, but always longer then 0 elements:
+;;;
+;;; -- We don't want to waste huge amounts of space no these vectors,
+;;; which are mostly required by things like SLOT-VALUE with a
+;;; variable slot name, so a constant extension over the minimum
+;;; size seems like a good choise.
+;;;
+;;; -- As long as the vector always has a length > 0
+;;; FIND-SLOT-DEFINITION doesn't need to handle the rare case of an
+;;; empty vector separately: it just returns a NIL.
+;;;
+;;; In addition to the slot-definition we also store the slot-location
+;;; and type-check function for instances of standard metaclasses, so
+;;; that SLOT-VALUE &co using variable slot names can get at them
+;;; without additional GF calls.
+;;;
+;;; Notes:
+;;; It would be probably better to store the vector in wrapper
+;;; instead: one less memory indirection, one less CLOS slot
+;;; access to get at it.
+;;;
+;;; It would also be nice to have STANDARD-INSTANCE-STRUCTURE-P
+;;; generic instead of checking versus STANDARD-CLASS and
+;;; FUNCALLABLE-STANDARD-CLASS.
+
+(defun find-slot-definition (class slot-name)
+ (dolist (slotd (class-slots class))
+ (when (eq slot-name (slot-definition-name slotd))
+ (return slotd))))
+
+(defun find-slot-cell (wrapper slot-name)
+ (declare (symbol slot-name))
+ (let* ((vector (layout-slot-table wrapper))
+ (index (rem (sxhash slot-name) (length vector))))
+ (declare (simple-vector vector) (index index)
+ (optimize (sb-c::insert-array-bounds-checks 0)))
+ (do ((plist (the list (svref vector index)) (cdr plist)))
+ ((not (consp plist)))
+ (let ((key (car plist)))
+ (setf plist (cdr plist))
+ (when (eq key slot-name)
+ (return (car plist)))))))
+
+(defun make-slot-table (class slots)
+ (let* ((n (+ (length slots) 2))
+ (vector (make-array n :initial-element nil))
+ (save-slot-location-p
+ (when (eq 'complete *boot-state*)
+ (let ((metaclass (class-of class)))
+ (or (eq metaclass *the-class-standard-class*)
+ (eq metaclass *the-class-funcallable-standard-class*)))))
+ (save-type-check-function-p (and save-slot-location-p (safe-p class))))
+ (flet ((add-to-vector (name slot)
+ (declare (symbol name)
+ (optimize (sb-c::insert-array-bounds-checks 0)))
+ (let ((index (rem (sxhash name) n)))
+ (setf (svref vector index)
+ (list* name (list* (if save-slot-location-p
+ (slot-definition-location slot)
+ ;; T tells SLOT-VALUE & SET-SLOT-VALUE
+ ;; that this is a non-standard class.
+ t)
+ (when save-type-check-function-p
+ (slot-definition-type-check-function slot))
+ slot)
+ (svref vector index))))))
+ (if (eq 'complete *boot-state*)
+ (dolist (slot slots)
+ (add-to-vector (slot-definition-name slot) slot))
+ (dolist (slot slots)
+ (add-to-vector (early-slot-definition-name slot) slot))))
+ vector))
projects / sbcl.git / blobdiff