ice-9/hcons.scm

   1 ;;; installed-scm-file
   2
   3 ;;;;    Copyright (C) 1995, 1996 Free Software Foundation, Inc.
   4 ;;;;
   5 ;;;; This program is free software; you can redistribute it and/or modify
   6 ;;;; it under the terms of the GNU General Public License as published by
   7 ;;;; the Free Software Foundation; either version 2, or (at your option)
   8 ;;;; any later version.
   9 ;;;;
  10 ;;;; This program is distributed in the hope that it will be useful,
  11 ;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 ;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 ;;;; GNU General Public License for more details.
  14 ;;;;
  15 ;;;; You should have received a copy of the GNU General Public License
  16 ;;;; along with this software; see the file COPYING.  If not, write to
  17 ;;;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
  18 ;;;;
  19
  20 \f
  21 (define-module  #/ice-9/hcons)
  22
  23 \f
  24 ;;; {Eq? hash-consing}
  25 ;;;
  26 ;;; A hash conser maintains a private universe of pairs s.t. if
  27 ;;; two cons calls pass eq? arguments, the pairs returned are eq?.
  28 ;;;
  29 ;;; A hash conser does not contribute life to the pairs it returns.
  30 ;;;
  31
  32 (define-public (hashq-cons-hash pair n)
  33   (modulo (logxor (hashq (car pair) 4194303)
  34                   (hashq (cdr pair) 4194303))
  35           n))
  36
  37 (define-public (hashq-cons-assoc key l)
  38   (and l (or (and (pair? l)
  39                   (pair? (car l))
  40                   (pair? (caar l))
  41                   (eq? (car key) (caaar l))
  42                   (eq? (cdr key) (cdaar l))
  43                   (car l))
  44              (hashq-cons-assoc key (cdr l)))))
  45
  46 (define-public (hashq-cons-get-handle table key)
  47   (hashx-get-handle hashq-cons-hash hashq-cons-assoc table key #f))
  48
  49 (define-public (hashq-cons-create-handle! table key init)
  50   (hashx-create-handle! hashq-cons-hash hashq-cons-assoc table key init))
  51
  52 (define-public (hashq-cons-ref table key)
  53   (hashx-ref hashq-cons-hash hashq-cons-assoc table key #f))
  54
  55 (define-public (hashq-cons-set! table key val)
  56   (hashx-set! hashq-cons-hash hashq-cons-assoc table key val))
  57
  58 (define-public (hashq-cons table a d)
  59   (car (hashq-cons-create-handle! table (cons a d) #f)))
  60
  61 (define-public (hashq-conser hash-tab-or-size)
  62   (let ((table (if (vector? hash-tab-or-size)
  63                    hash-tab-or-size
  64                    (make-doubly-weak-hash-table hash-tab-or-size))))
  65     (lambda (a d) (hashq-cons table a d))))
  66
  67
  68 \f
  69
  70 (define-public (make-gc-buffer n)
  71   (let ((ring (make-list n #f)))
  72     (append! ring ring)
  73     (lambda (next)
  74       (set-car! ring next)
  75       (set! ring (cdr ring))
  76       next)))