1.0.8.15: making SBCL sources Git more friendly

[sbcl.git] / src / pcl / slots-boot.lisp

diff --git a/src/pcl/slots-boot.lisp b/src/pcl/slots-boot.lisp
index 6bef614..9f416cf 100644 (file)
--- a/src/pcl/slots-boot.lisp
+++ b/src/pcl/slots-boot.lisp
@@ -521,3 +521,59 @@
     (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.
+;;;
+;;; As of 1.0.7.26 SBCL hashes the effective slot definitions 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 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.
+
+(defun find-slot-definition (class slot-name)
+  (declare (symbol slot-name))
+  (let* ((vector (class-slot-vector class))
+         (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-vector (slots)
+  (let* ((n (+ (length slots) 2))
+         (vector (make-array n :initial-element nil)))
+    (flet ((add-to-vector (name slot)
+             (declare (symbol name)
+                      (optimize (sb-c::insert-array-bounds-checks 0)))
+             (setf (svref vector (rem (sxhash name) n))
+                   (list* name slot (svref vector (rem (sxhash name) n))))))
+      (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))