259 lines
9.1 KiB
Scheme
259 lines
9.1 KiB
Scheme
;; -*-scheme-*-
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;;; Mes --- Maxwell Equations of Software
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;;; Copyright (c) 1993-2004 by Richard Kelsey and Jonathan Rees.
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;;; Copyright © 2016 Jan Nieuwenhuizen <janneke@gnu.org>
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;;;
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;;; This file is part of Mes.
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;;;
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;;; Mes is free software; you can redistribute it and/or modify it
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;;; under the terms of the GNU General Public License as published by
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;;; the Free Software Foundation; either version 3 of the License, or (at
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;;; your option) any later version.
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;;;
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;;; Mes is distributed in the hope that it will be useful, but
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;;; WITHOUT ANY WARRANTY; without even the implied warranty of
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;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;;; GNU General Public License for more details.
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;;;
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;;; You should have received a copy of the GNU General Public License
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;;; along with Mes. If not, see <http://www.gnu.org/licenses/>.
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;;; Commentary:
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;;; record.mes is loaded after record-0.mes. It provides a
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;;; nonstandard record type that SRFI-9 can be trivially implemented
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;;; on. Adapted from scheme48-1.1/scheme/rts/record.scm
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;;; Code:
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;;; Copyright (c) 1993-2004 by Richard Kelsey and Jonathan Rees. See file COPYING.
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;;; scheme48-1.1/COPYING
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;; Copyright (c) 1993-2004 Richard Kelsey and Jonathan Rees
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;; All rights reserved.
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;; Redistribution and use in source and binary forms, with or without
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;; modification, are permitted provided that the following conditions
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;; are met:
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;; 1. Redistributions of source code must retain the above copyright
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;; notice, this list of conditions and the following disclaimer.
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;; 2. Redistributions in binary form must reproduce the above copyright
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;; notice, this list of conditions and the following disclaimer in the
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;; documentation and/or other materials provided with the distribution.
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;; 3. The name of the authors may not be used to endorse or promote products
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;; derived from this software without specific prior written permission.
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;; THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
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;; IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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;; OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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;; IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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;; INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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;; NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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;; DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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;; THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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;; (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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;; THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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;;;; Records
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; Every record in the image is assumed to be made either by MAKE-RECORD-TYPE
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; or by a procedure returned by record-constructor. A record-type is a
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; record that describes a type of record. At the end of the file we create
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; a record type that describes record types.
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; We number the record types for debugging purposes.
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(define *record-type-uid* -1)
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; This is the record type that describes record types. It is set a the end
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; of the file. Its first slot points to itself.
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(define *record-type* #f)
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; Make a record type from a name, used for printing and debugging, and
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; a list of field names.
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;
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; The VM references both the record type and the resumer, so their offsets
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; should not be changed.
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(define (make-record-type name field-names)
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(set! *record-type-uid* (+ *record-type-uid* 1))
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(let ((r (make-record 7 (unspecific))))
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(record-set! r 0 *record-type*)
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(record-set! r 1 default-record-resumer)
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(record-set! r 2 *record-type-uid*)
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(record-set! r 3 name)
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(record-set! r 4 field-names)
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(record-set! r 5 (length field-names))
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(record-set! r 6 (make-default-record-discloser name))
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r))
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(define (record-type? obj)
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(and (record? obj)
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(eq? (record-type obj) *record-type*)))
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; The various fields in a record type.
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(define (record-type-resumer rt) (record-ref rt 1))
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(define (set-record-type-resumer! rt r) (record-set! rt 1 r))
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(define (record-type-uid rt) (record-ref rt 2))
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(define (record-type-name rt) (record-ref rt 3))
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(define (record-type-field-names rt) (record-ref rt 4))
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(define (record-type-number-of-fields rt) (record-ref rt 5))
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(define (record-type-discloser rt) (record-ref rt 6))
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(define (set-record-type-discloser! rt d) (record-set! rt 6 d))
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; This is a hack; it is read by the script that makes c/scheme48.h.
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(define record-type-fields
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'(resumer uid name field-names number-of-fields discloser))
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;----------------
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; Given a record type and the name of a field, return the field's index.
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(define (record-field-index rt name)
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(let loop ((names (record-type-field-names rt))
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(i 1))
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(cond ((null? names)
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(error "unknown field"
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(record-type-name rt)
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name))
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((eq? name (car names))
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i)
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(else
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(loop (cdr names) (+ i 1))))))
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; Return procedure for contstruction records of type RT. NAMES is a list of
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; field names which the constructor will take as arguments. Other fields are
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; uninitialized.
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(define (record-constructor rt names)
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(let ((indexes (map (lambda (name)
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(record-field-index rt name))
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names))
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(size (+ 1 (record-type-number-of-fields rt))))
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(lambda args
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(let ((r (make-record size (unspecific))))
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(record-set! r 0 rt)
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(let loop ((is indexes) (as args))
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(if (null? as)
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(if (null? is)
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r
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(error "too few arguments to record constructor"
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rt names args))
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(if (null? is)
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(error "too many arguments to record constructor"
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rt names args)
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(begin (record-set! r (car is) (car as))
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(loop (cdr is) (cdr as))))))))))
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; Making accessors, modifiers, and predicates for record types.
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(define (record-accessor rt name)
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(let ((index (record-field-index rt name))
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(error-cruft `(record-accessor ,rt ',name)))
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(lambda (r)
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(if (eq? (record-type r) rt)
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(record-ref r index)
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(call-error "invalid record access" error-cruft r)))))
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(define (record-modifier rt name)
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(let ((index (record-field-index rt name))
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(error-cruft `(record-modifier ,rt ',name)))
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(lambda (r x)
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(if (eq? (record-type r) rt)
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(record-set! r index x)
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(call-error "invalid record modification" error-cruft r x)))))
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(define (record-predicate rt)
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(lambda (x)
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(and (record? x)
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(eq? (record-type x) rt))))
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;----------------
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; A discloser is a procedure that takes a record of a particular type and
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; returns a list whose head is a string or symbol and whose tail is other
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; stuff.
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;
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; Set the discloser for record type RT.
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(define (define-record-discloser rt proc)
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(if (and (record-type? rt)
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(procedure? proc))
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(set-record-type-discloser! rt proc)
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(call-error "invalid argument" define-record-discloser rt proc)))
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; By default we just return the name of the record type.
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(define (make-default-record-discloser record-type-name)
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(lambda (r)
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(list record-type-name)))
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; DISCLOSE-RECORD calls the record's discloser procedure to obtain a list.
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(define (disclose-record r)
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(if (record? r)
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(let ((rt (record-type r)))
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(if (record-type? rt)
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((record-type-discloser rt) r)
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#f))
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#f))
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;----------------
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; A resumer is a procedure that the VM calls on all records of a given
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; type on startup.
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;
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; A resumer may be:
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; #t -> do nothing on startup.
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; #f -> records of this type do not survive a dump/resume; in images they
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; are replaced by their first slot (so we make sure they have one)
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; a one-argument procedure -> pass the record to this procedure
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;
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; Resumers are primarily intended for use by external code which keeps
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; fields in records which do not survive a dump under their own power.
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; For example, a record may contain a reference to a OS-dependent value.
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;
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; Resumers are called by the VM on startup.
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(define (define-record-resumer rt resumer)
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(if (and (record-type? rt)
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(or (eq? #t resumer)
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(and (eq? #f resumer)
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(< 0 (record-type-number-of-fields rt)))
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(procedure? resumer)))
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(set-record-type-resumer! rt resumer)
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(call-error "invalid argument" define-record-resumer rt resumer)))
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; By default we leave records alone.
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(define default-record-resumer
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#t)
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(define (initialize-records! resumer-records)
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(if (vector? resumer-records)
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(do ((i 0 (+ i 1)))
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((= i (vector-length resumer-records)))
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(resume-record (vector-ref resumer-records i)))))
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(define (resume-record record)
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((record-type-resumer (record-type record))
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record))
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;----------------
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; Initializing *RECORD-TYPE* and making a type.
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(set! *record-type*
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(make-record-type 'record-type record-type-fields))
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(record-set! *record-type* 0 *record-type*)
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(define :record-type *record-type*)
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(define-record-discloser :record-type
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(lambda (rt)
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(list 'record-type
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(record-type-uid rt)
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(record-type-name rt))))
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