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;;;
;;; fixhash.lisp
;;;
;;; Created: 2005-03-19 by Zach Beane <xach@xach.com>
;;;
;;; A hashtable whose keys and values are known to be fixnums^Wof a
;;; fixed, relatively small size. Sadly, not small enough to be
;;; fixnums on LispWorks.
;;;
;;; This table isn't general; it assumes that the compressor never
;;; uses zero for a key.
;;;
;;; Copyright (c) 2005 Zachary Beane, All Rights Reserved
;;;
;;; Redistribution and use in source and binary forms, with or without
;;; modification, are permitted provided that the following conditions
;;; are met:
;;;
;;; * Redistributions of source code must retain the above copyright
;;; notice, this list of conditions and the following disclaimer.
;;;
;;; * Redistributions in binary form must reproduce the above
;;; copyright notice, this list of conditions and the following
;;; disclaimer in the documentation and/or other materials
;;; provided with the distribution.
;;;
;;; THIS SOFTWARE IS PROVIDED BY THE AUTHOR 'AS IS' AND ANY EXPRESSED
;;; OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
;;; WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
;;; ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
;;; DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
;;; DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
;;; GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
;;; INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
;;; WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
;;; NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
;;; SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
;;;
;;; $Id: fixhash.lisp,v 1.7 2005/04/01 21:55:24 xach Exp $
(defpackage :fixhash
(:use :cl)
(:export :make-fixhash-table
:getfixhash
:clrfixhash))
(in-package :fixhash)
(deftype fixhash-integer ()
"#xFFFFFF is out of fixnum range on LispWorks."
'(integer 0 #xFFFFFF))
(defparameter *sizes*
#(4096
16384
65536
131072))
(defstruct fixhash-table
(level 0 :type fixnum)
(size 4096 :type fixnum)
(keys/values (make-array (* 4096 2)
:element-type 'fixhash-integer
:initial-element 0)
:type (simple-array fixhash-integer (*)))
(last-key 0 :type fixhash-integer)
(last-key-pos 0 :type fixnum))
(defmethod print-object ((fixhash-table fixhash-table) stream)
(print-unreadable-object (fixhash-table stream :type t :identity t)
(format stream "~D/~D"
(fixhash-table-level fixhash-table)
(fixhash-table-size fixhash-table))))
(defun rehash (table)
(declare (optimize (speed 3) (safety 0)))
(let ((level (fixhash-table-level table))
(keys/values (fixhash-table-keys/values table))
(size (fixhash-table-size table)))
(when (= 3 level)
(error "Hash table full"))
(let* ((new-size (svref *sizes* (incf level)))
(new-keys/values (make-array (the fixnum (* new-size 2))
:initial-element 0
:element-type 'fixhash-integer)))
(dotimes (i (* size 2))
(setf (aref new-keys/values i) (aref keys/values i)))
(setf (fixhash-table-keys/values table) new-keys/values
(fixhash-table-size table) new-size
(fixhash-table-level table) level))))
(defun getfixhash (k fixhash-table)
(declare (optimize (speed 3) (safety 0) (debug 0)
#+lispworks (hcl:fixnum-safety 0))
(type fixhash-integer k))
(let* ((size (fixhash-table-size fixhash-table))
(mask (1- size))
(h1 (logand k mask))
(h2 (logior 1 (mod k (1- size))))
(j 0)
(i*h2 0)
(table (fixhash-table-keys/values fixhash-table)))
(declare (type (integer 0 131072) size mask h1 h2 j i*h2))
(dotimes (i size (and (rehash fixhash-table) 0))
(declare (fixnum i))
(incf i*h2 h2)
(setf j (ash (logand mask (+ h1 i*h2)) 1))
(let ((kt (aref table j)))
(when (= k kt)
(return (aref table (1+ j))))
(when (zerop kt)
(setf (fixhash-table-last-key fixhash-table) k
(fixhash-table-last-key-pos fixhash-table) j)
(return 0))))))
(defun (setf getfixhash) (new-value k fixhash-table)
(declare (optimize (speed 3) (safety 0) (debug 0)
#+lispworks (hcl:fixnum-safety 0))
(type fixhash-integer new-value k))
(let ((last-key (fixhash-table-last-key fixhash-table))
(last-key-pos (fixhash-table-last-key-pos fixhash-table))
(table (fixhash-table-keys/values fixhash-table)))
(if (= last-key k)
(setf (aref table last-key-pos) k
(aref table (1+ last-key-pos)) new-value)
(let* ((size (fixhash-table-size fixhash-table))
(mask (1- size))
(h1 (logand k mask))
(h2 (logior 1 (mod k (1- size))))
(i*h2 0)
(j 0))
(declare (type (integer 0 131072) h2 h1 i*h2 size mask))
(dotimes (i size)
(declare (fixnum i))
(incf i*h2 h2)
(setf j (ash (logand mask (+ h1 i*h2)) 1))
(let ((kt (aref table j)))
(when (or (= k kt) (zerop kt))
(setf (aref table j) k
(aref table (1+ j)) new-value)
(return new-value))))))))
(defun clrfixhash (fixhash-table)
(declare (optimize (speed 3) (safety 0)
#+lispworks (hcl:fixnum-safety 0)))
(let ((table (fixhash-table-keys/values fixhash-table)))
(dotimes (i (length table))
(declare (fixnum i))
(setf (aref table i) 0)))
fixhash-table)
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