#| -*-Scheme-*-

Copyright (C) 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994,
    1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
    2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016,
    2017, 2018, 2019 Massachusetts Institute of Technology

This file is part of MIT/GNU Scheme.

MIT/GNU Scheme is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or (at
your option) any later version.

MIT/GNU Scheme is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

You should have received a copy of the GNU General Public License
along with MIT/GNU Scheme; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301,
USA.

|#

;;;; Tagged Vectors

(declare (usual-integrations))

;;; These procedures are optimized for safety.  Applications that need
;;; speed are assumed to break this abstraction and use "%record"
;;; calls to construct and access tagged vectors.

(define (make-tagged-vector tag length)
  (guarantee dispatch-tag? tag 'MAKE-TAGGED-VECTOR)
  (guarantee-index-integer length 'MAKE-TAGGED-VECTOR)
  (%make-record tag (fix:+ length 1) record-slot-uninitialized))

(define (tagged-vector tag . elements)
  (guarantee dispatch-tag? tag 'MAKE-TAGGED-VECTOR)
  (apply %record tag elements))

(define (tagged-vector? object)
  (and (%record? object)
       (dispatch-tag? (%record-ref object 0))))
(register-predicate! tagged-vector? 'tagged-vector '<= %record?)

(define (tagged-vector-tag vector)
  (guarantee-tagged-vector vector 'TAGGED-VECTOR-TAG)
  (%record-ref vector 0))

(define (set-tagged-vector-tag! vector tag)
  (guarantee-tagged-vector vector 'SET-TAGGED-VECTOR-TAG!)
  (guarantee dispatch-tag? tag 'SET-TAGGED-VECTOR-TAG!)
  (%record-set! vector 0 tag))

(define (tagged-vector-length vector)
  (guarantee-tagged-vector vector 'TAGGED-VECTOR-LENGTH)
  (fix:- (%record-length vector) 1))

(define (tagged-vector-element vector index)
  (guarantee-tagged-vector-ref vector index 'TAGGED-VECTOR-ELEMENT)
  (%record-ref vector (fix:+ index 1)))

(define (set-tagged-vector-element! vector index value)
  (guarantee-tagged-vector-ref vector index 'SET-TAGGED-VECTOR-ELEMENT!)
  (%record-set! vector (fix:+ index 1) value))

(define (tagged-vector-element-initialized? vector index)
  (guarantee-tagged-vector-ref vector index
			       'TAGGED-VECTOR-ELEMENT-INITIALIZED?)
  (not (eq? (%record-ref vector (fix:+ index 1)) record-slot-uninitialized)))

(define (guarantee-tagged-vector vector caller)
  (if (not (tagged-vector? vector))
      (error:wrong-type-argument vector "tagged vector" caller)))

(define (guarantee-tagged-vector-ref vector index caller)
  (guarantee-tagged-vector vector caller)
  (guarantee-index-integer index caller)
  (if (not (fix:< index (fix:- (%record-length vector) 1)))
      (error:bad-range-argument index caller)))

(define (guarantee-index-integer index caller)
  (if (not (and (fix:fixnum? index) (fix:>= index 0)))
      (error:wrong-type-argument vector "non-negative fixnum" caller)))

(define record-slot-uninitialized
  (intern "#[record-slot-uninitialized]"))