;;;; functions to implement arrays

;;;; This software is part of the SBCL system. See the README file for
;;;; more information.
;;;;
;;;; This software is derived from the CMU CL system, which was
;;;; written at Carnegie Mellon University and released into the
;;;; public domain. The software is in the public domain and is
;;;; provided with absolutely no warranty. See the COPYING and CREDITS
;;;; files for more information.

(in-package "SB!IMPL")

#!-sb-fluid
(declaim (inline fill-pointer array-has-fill-pointer-p adjustable-array-p
                 array-displacement))

;;;; miscellaneous accessor functions

;;; These functions are only needed by the interpreter, 'cause the
;;; compiler inlines them.
(macrolet ((def (name)
             `(progn
                (defun ,name (array)
                  (,name array))
                (defun (setf ,name) (value array)
                  (setf (,name array) value)))))
  (def %array-fill-pointer)
  (def %array-fill-pointer-p)
  (def %array-available-elements)
  (def %array-data-vector)
  (def %array-displacement)
  (def %array-displaced-p)
  (def %array-diplaced-from))

(defun %array-rank (array)
  (%array-rank array))

(defun %array-dimension (array axis)
  (%array-dimension array axis))

(defun %set-array-dimension (array axis value)
  (%set-array-dimension array axis value))

(defun %check-bound (array bound index)
  (declare (type index bound)
           (fixnum index))
  (%check-bound array bound index))

(defun %with-array-data/fp (array start end)
  (%with-array-data-macro array start end :check-bounds t :check-fill-pointer t))

(defun %with-array-data (array start end)
  (%with-array-data-macro array start end :check-bounds t :check-fill-pointer nil))

(defun %data-vector-and-index (array index)
  (if (array-header-p array)
      (multiple-value-bind (vector index)
          (%with-array-data array index nil)
        (values vector index))
      (values array index)))

;;;; MAKE-ARRAY
(eval-when (:compile-toplevel :execute)
  (sb!xc:defmacro pick-vector-type (type &rest specs)
    `(cond ,@(mapcar (lambda (spec)
                       `(,(if (eq (car spec) t)
                              t
                              `(subtypep ,type ',(car spec)))
                         ,@(cdr spec)))
                     specs))))

;;; These functions are used in the implementation of MAKE-ARRAY for
;;; complex arrays. There are lots of transforms to simplify
;;; MAKE-ARRAY for various easy cases, but not for all reasonable
;;; cases, so e.g. as of sbcl-0.6.6 we still make full calls to
;;; MAKE-ARRAY for any non-simple array. Thus, there's some value to
;;; making this somewhat efficient, at least not doing full calls to
;;; SUBTYPEP in the easy cases.
(defun %vector-widetag-and-n-bits (type)
  (case type
    ;; Pick off some easy common cases.
    ;;
    ;; (Perhaps we should make a much more exhaustive table of easy
    ;; common cases here. Or perhaps the effort would be better spent
    ;; on smarter compiler transforms which do the calculation once
    ;; and for all in any reasonable user programs.)
    ((t)
     (values #.sb!vm:simple-vector-widetag #.sb!vm:n-word-bits))
    ((base-char standard-char #!-sb-unicode character)
     (values #.sb!vm:simple-base-string-widetag #.sb!vm:n-byte-bits))
    #!+sb-unicode
    ((character)
     (values #.sb!vm:simple-character-string-widetag #.sb!vm:n-word-bits))
    ((bit)
     (values #.sb!vm:simple-bit-vector-widetag 1))
    ;; OK, we have to wade into SUBTYPEPing after all.
    (t
     (unless *type-system-initialized*
       (bug "SUBTYPEP dispatch for MAKE-ARRAY before the type system is ready"))
     #.`(pick-vector-type type
         ,@(map 'list
                (lambda (saetp)
                  `(,(sb!vm:saetp-specifier saetp)
                    (values ,(sb!vm:saetp-typecode saetp)
                            ,(sb!vm:saetp-n-bits saetp))))
                sb!vm:*specialized-array-element-type-properties*)))))

(defun %complex-vector-widetag (type)
  (case type
    ;; Pick off some easy common cases.
    ((t)
     #.sb!vm:complex-vector-widetag)
    ((base-char #!-sb-unicode character)
     #.sb!vm:complex-base-string-widetag)
    #!+sb-unicode
    ((character)
     #.sb!vm:complex-character-string-widetag)
    ((nil)
     #.sb!vm:complex-vector-nil-widetag)
    ((bit)
     #.sb!vm:complex-bit-vector-widetag)
    ;; OK, we have to wade into SUBTYPEPing after all.
    (t
     (pick-vector-type type
       (nil #.sb!vm:complex-vector-nil-widetag)
       #!-sb-unicode
       (character #.sb!vm:complex-base-string-widetag)
       #!+sb-unicode
       (base-char #.sb!vm:complex-base-string-widetag)
       #!+sb-unicode
       (character #.sb!vm:complex-character-string-widetag)
       (bit #.sb!vm:complex-bit-vector-widetag)
       (t #.sb!vm:complex-vector-widetag)))))

(defun make-array (dimensions &key
                              (element-type t)
                              (initial-element nil initial-element-p)
                              (initial-contents nil initial-contents-p)
                              adjustable fill-pointer
                              displaced-to displaced-index-offset)
  (let* ((dimensions (if (listp dimensions) dimensions (list dimensions)))
         (array-rank (length (the list dimensions)))
         (simple (and (null fill-pointer)
                      (not adjustable)
                      (null displaced-to))))
    (declare (fixnum array-rank))
    (when (and displaced-index-offset (null displaced-to))
      (error "can't specify :DISPLACED-INDEX-OFFSET without :DISPLACED-TO"))
    (when (and displaced-to
               (arrayp displaced-to)
               (not (equal (array-element-type displaced-to)
                           (upgraded-array-element-type element-type))))
      (error "Array element type of :DISPLACED-TO array does not match specified element type"))
    (if (and simple (= array-rank 1))
        ;; it's a (SIMPLE-ARRAY * (*))
        (multiple-value-bind (type n-bits)
            (%vector-widetag-and-n-bits element-type)
          (declare (type (unsigned-byte 8) type)
                   (type (integer 0 256) n-bits))
          (let* ((length (car dimensions))
                 (array (allocate-vector
                         type
                         length
                         (ceiling
                          (* (if (or (= type sb!vm:simple-base-string-widetag)
                                     #!+sb-unicode
                                     (= type
                                        sb!vm:simple-character-string-widetag))
                                 (1+ length)
                                 length)
                             n-bits)
                          sb!vm:n-word-bits))))
            (declare (type index length))
            (when initial-element-p
              (fill array initial-element))
            (when initial-contents-p
              (when initial-element-p
                (error "can't specify both :INITIAL-ELEMENT and ~
                       :INITIAL-CONTENTS"))
              (unless (= length (length initial-contents))
                (error "There are ~W elements in the :INITIAL-CONTENTS, but ~
                       the vector length is ~W."
                       (length initial-contents)
                       length))
              (replace array initial-contents))
            array))
        ;; it's either a complex array or a multidimensional array.
        (let* ((total-size (reduce #'* dimensions))
               (data (or displaced-to
                         (data-vector-from-inits
                          dimensions total-size element-type
                          initial-contents initial-contents-p
                          initial-element initial-element-p)))
               (array (make-array-header
                       (cond ((= array-rank 1)
                              (%complex-vector-widetag element-type))
                             (simple sb!vm:simple-array-widetag)
                             (t sb!vm:complex-array-widetag))
                       array-rank)))
          (cond (fill-pointer
                 (unless (= array-rank 1)
                   (error "Only vectors can have fill pointers."))
                 (let ((length (car dimensions)))
                   (declare (fixnum length))
                   (setf (%array-fill-pointer array)
                     (cond ((eq fill-pointer t)
                            length)
                           (t
                            (unless (and (fixnump fill-pointer)
                                         (>= fill-pointer 0)
                                         (<= fill-pointer length))
                              ;; FIXME: should be TYPE-ERROR?
                              (error "invalid fill-pointer ~W"
                                     fill-pointer))
                            fill-pointer))))
                 (setf (%array-fill-pointer-p array) t))
                (t
                 (setf (%array-fill-pointer array) total-size)
                 (setf (%array-fill-pointer-p array) nil)))
          (setf (%array-available-elements array) total-size)
          (setf (%array-data-vector array) data)
          (setf (%array-displaced-from array) nil)
          (cond (displaced-to
                 (when (or initial-element-p initial-contents-p)
                   (error "Neither :INITIAL-ELEMENT nor :INITIAL-CONTENTS ~
                   can be specified along with :DISPLACED-TO"))
                 (let ((offset (or displaced-index-offset 0)))
                   (when (> (+ offset total-size)
                            (array-total-size displaced-to))
                     (error "~S doesn't have enough elements." displaced-to))
                   (setf (%array-displacement array) offset)
                   (setf (%array-displaced-p array) t)
                   (%save-displaced-array-backpointer array data)))
                (t
                 (setf (%array-displaced-p array) nil)))
          (let ((axis 0))
            (dolist (dim dimensions)
              (setf (%array-dimension array axis) dim)
              (incf axis)))
          array))))

(defun make-static-vector (length &key
                           (element-type '(unsigned-byte 8))
                           (initial-contents nil initial-contents-p)
                           (initial-element nil initial-element-p))
  "Allocate vector of LENGTH elements in static space. Only allocation
of specialized arrays is supported."
  ;; STEP 1: check inputs fully
  ;;
  ;; This way of doing explicit checks before the vector is allocated
  ;; is expensive, but probably worth the trouble as once we've allocated
  ;; the vector we have no way to get rid of it anymore...
  (when (eq t (upgraded-array-element-type element-type))
    (error "Static arrays of type ~S not supported."
           element-type))
  (when initial-contents-p
    (when initial-element-p
      (error "can't specify both :INITIAL-ELEMENT and :INITIAL-CONTENTS"))
    (unless (= length (length initial-contents))
      (error "There are ~W elements in the :INITIAL-CONTENTS, but the ~
              vector length is ~W."
             (length initial-contents)
             length))
    (unless (every (lambda (x) (typep x element-type)) initial-contents)
      (error ":INITIAL-CONTENTS contains elements not of type ~S."
             element-type)))
  (when initial-element-p
    (unless (typep initial-element element-type)
      (error ":INITIAL-ELEMENT ~S is not of type ~S."
             initial-element element-type)))
  ;; STEP 2
  ;;
  ;; Allocate and possibly initialize the vector.
  (multiple-value-bind (type n-bits)
      (sb!impl::%vector-widetag-and-n-bits element-type)
    (let ((vector
           (allocate-static-vector type length
                                   (ceiling (* length n-bits)
                                            sb!vm:n-word-bits))))
      (cond (initial-element-p
             (fill vector initial-element))
            (initial-contents-p
             (replace vector initial-contents))
            (t
             vector)))))

;;; DATA-VECTOR-FROM-INITS returns a simple vector that has the
;;; specified array characteristics. Dimensions is only used to pass
;;; to FILL-DATA-VECTOR for error checking on the structure of
;;; initial-contents.
(defun data-vector-from-inits (dimensions total-size element-type
                               initial-contents initial-contents-p
                               initial-element initial-element-p)
  (when (and initial-contents-p initial-element-p)
    (error "cannot supply both :INITIAL-CONTENTS and :INITIAL-ELEMENT to
            either MAKE-ARRAY or ADJUST-ARRAY."))
  (let ((data (if initial-element-p
                  (make-array total-size
                              :element-type element-type
                              :initial-element initial-element)
                  (make-array total-size
                              :element-type element-type))))
    (cond (initial-element-p
           (unless (simple-vector-p data)
             (unless (typep initial-element element-type)
               (error "~S cannot be used to initialize an array of type ~S."
                      initial-element element-type))
             (fill (the vector data) initial-element)))
          (initial-contents-p
           (fill-data-vector data dimensions initial-contents)))
    data))

(defun vector (&rest objects)
  #!+sb-doc
  "Construct a SIMPLE-VECTOR from the given objects."
  (coerce (the list objects) 'simple-vector))


;;;; accessor/setter functions

;;; Dispatch to an optimized routine the data vector accessors for
;;; each different specialized vector type. Do dispatching by looking
;;; up the widetag in the array rather than with the typecases, which
;;; as of 1.0.5 compiles to a naive sequence of linear TYPEPs. Also
;;; provide separate versions where bounds checking has been moved
;;; from the callee to the caller, since it's much cheaper to do once
;;; the type information is available. Finally, for each of these
;;; routines also provide a slow path, taken for arrays that are not
;;; vectors or not simple.
(macrolet ((def (name table-name)
             `(progn
                (defglobal ,table-name (make-array ,(1+ sb!vm:widetag-mask)))
                (defmacro ,name (array-var)
                  `(the function
                     (let ((tag 0))
                       (when (sb!vm::%other-pointer-p ,array-var)
                         (setf tag (%other-pointer-widetag ,array-var)))
                       (svref ,',table-name tag)))))))
  (def !find-data-vector-setter %%data-vector-setters%%)
  (def !find-data-vector-setter/check-bounds %%data-vector-setters/check-bounds%%)
  (def !find-data-vector-reffer %%data-vector-reffers%%)
  (def !find-data-vector-reffer/check-bounds %%data-vector-reffers/check-bounds%%))

(macrolet ((%ref (accessor-getter extra-params)
             `(funcall (,accessor-getter array) array index ,@extra-params))
           (define (accessor-name slow-accessor-name accessor-getter
                                  extra-params check-bounds)
             `(progn
                (defun ,accessor-name (array index ,@extra-params)
                  (declare (optimize speed
                                     ;; (SAFETY 0) is ok. All calls to
                                     ;; these functions are generated by
                                     ;; the compiler, so argument count
                                     ;; checking isn't needed. Type checking
                                     ;; is done implicitly via the widetag
                                     ;; dispatch.
                                     (safety 0)))
                  (%ref ,accessor-getter ,extra-params))
                (defun ,slow-accessor-name (array index ,@extra-params)
                  (declare (optimize speed (safety 0)))
                  (if (not (%array-displaced-p array))
                      ;; The reasonably quick path of non-displaced complex
                      ;; arrays.
                      (let ((array (%array-data-vector array)))
                        (%ref ,accessor-getter ,extra-params))
                      ;; The real slow path.
                      (with-array-data
                          ((vector array)
                           (index (locally
                                      (declare (optimize (speed 1) (safety 1)))
                                    (,@check-bounds index)))
                           (end)
                           :force-inline t)
                        (declare (ignore end))
                        (,accessor-name vector index ,@extra-params)))))))
  (define hairy-data-vector-ref slow-hairy-data-vector-ref
    !find-data-vector-reffer
    nil (progn))
  (define hairy-data-vector-set slow-hairy-data-vector-set
    !find-data-vector-setter
    (new-value) (progn))
  (define hairy-data-vector-ref/check-bounds
      slow-hairy-data-vector-ref/check-bounds
    !find-data-vector-reffer/check-bounds
    nil (%check-bound array (array-dimension array 0)))
  (define hairy-data-vector-set/check-bounds
      slow-hairy-data-vector-set/check-bounds
    !find-data-vector-setter/check-bounds
    (new-value) (%check-bound array (array-dimension array 0))))

(defun hairy-ref-error (array index &optional new-value)
  (declare (ignore index new-value))
  (error 'type-error
         :datum array
         :expected-type 'vector))

;;; Populate the dispatch tables.
(macrolet ((define-reffer (saetp check-form)
             (let* ((type (sb!vm:saetp-specifier saetp))
                    (atype `(simple-array ,type (*))))
               `(named-lambda optimized-data-vector-ref (vector index)
                  (declare (optimize speed (safety 0)))
                  (data-vector-ref (the ,atype vector)
                                   (locally
                                       (declare (optimize (safety 1)))
                                     (the index
                                       (,@check-form index)))))))
           (define-setter (saetp check-form)
             (let* ((type (sb!vm:saetp-specifier saetp))
                    (atype `(simple-array ,type (*))))
               `(named-lambda optimized-data-vector-set (vector index new-value)
                  (declare (optimize speed (safety 0)))
                  (data-vector-set (the ,atype vector)
                                   (locally
                                       (declare (optimize (safety 1)))
                                     (the index
                                       (,@check-form index)))
                                   (locally
                                       ;; SPEED 1 needed to avoid the compiler
                                       ;; from downgrading the type check to
                                       ;; a cheaper one.
                                       (declare (optimize (speed 1)
                                                          (safety 1)))
                                     (the ,type new-value)))
                  ;; For specialized arrays, the return from
                  ;; data-vector-set would have to be reboxed to be a
                  ;; (Lisp) return value; instead, we use the
                  ;; already-boxed value as the return.
                  new-value)))
           (define-reffers (symbol deffer check-form slow-path)
             `(progn
                ;; FIXME/KLUDGE: can't just FILL here, because genesis doesn't
                ;; preserve the binding, so re-initiaize as NS doesn't have
                ;; the energy to figure out to change that right now.
                (setf ,symbol (make-array (1+ sb!vm::widetag-mask)
                                          :initial-element #'hairy-ref-error))
                ,@(loop for widetag in '(sb!vm:complex-vector-widetag
                                         sb!vm:complex-vector-nil-widetag
                                         sb!vm:complex-bit-vector-widetag
                                         #!+sb-unicode sb!vm:complex-character-string-widetag
                                         sb!vm:complex-base-string-widetag
                                         sb!vm:simple-array-widetag
                                         sb!vm:complex-array-widetag)
                        collect `(setf (svref ,symbol ,widetag) ,slow-path))
                ,@(loop for saetp across sb!vm:*specialized-array-element-type-properties*
                        for widetag = (sb!vm:saetp-typecode saetp)
                        collect `(setf (svref ,symbol ,widetag)
                                       (,deffer ,saetp ,check-form))))))
  (defun !hairy-data-vector-reffer-init ()
    (define-reffers %%data-vector-reffers%% define-reffer
      (progn)
      #'slow-hairy-data-vector-ref)
    (define-reffers %%data-vector-setters%% define-setter
      (progn)
      #'slow-hairy-data-vector-set)
    (define-reffers %%data-vector-reffers/check-bounds%% define-reffer
      (%check-bound vector (length vector))
      #'slow-hairy-data-vector-ref/check-bounds)
    (define-reffers %%data-vector-setters/check-bounds%% define-setter
      (%check-bound vector (length vector))
      #'slow-hairy-data-vector-set/check-bounds)))

;;; (Ordinary DATA-VECTOR-REF usage compiles into a vop, but
;;; DATA-VECTOR-REF is also FOLDABLE, and this ordinary function
;;; definition is needed for the compiler to use in constant folding.)
(defun data-vector-ref (array index)
  (hairy-data-vector-ref array index))

(defun data-vector-ref-with-offset (array index offset)
  (hairy-data-vector-ref array (+ index offset)))

(defun invalid-array-p (array)
  (and (array-header-p array)
       (consp (%array-displaced-p array))))

(declaim (ftype (function (array) nil) invalid-array-error))
(defun invalid-array-error (array)
  (aver (array-header-p array))
  ;; Array invalidation stashes the original dimensions here...
  (let ((dims (%array-displaced-p array))
        (et (array-element-type array)))
    (error 'invalid-array-error
           :datum array
           :expected-type
           (if (cdr dims)
               `(array ,et ,dims)
               `(vector ,et ,@dims)))))

(declaim (ftype (function (array integer integer &optional t) nil)
                invalid-array-index-error))
(defun invalid-array-index-error (array index bound &optional axis)
  (if (invalid-array-p array)
      (invalid-array-error array)
      (error 'invalid-array-index-error
             :array array
             :axis axis
             :datum index
             :expected-type `(integer 0 (,bound)))))

;;; SUBSCRIPTS has a dynamic-extent list structure and is destroyed
(defun %array-row-major-index (array subscripts
                                     &optional (invalid-index-error-p t))
  (declare (array array)
           (list subscripts))
  (let ((rank (array-rank array)))
    (unless (= rank (length subscripts))
      (error "wrong number of subscripts, ~W, for array of rank ~W"
             (length subscripts) rank))
    (if (array-header-p array)
        (do ((subs (nreverse subscripts) (cdr subs))
             (axis (1- (array-rank array)) (1- axis))
             (chunk-size 1)
             (result 0))
            ((null subs) result)
          (declare (list subs) (fixnum axis chunk-size result))
          (let ((index (car subs))
                (dim (%array-dimension array axis)))
            (declare (fixnum dim))
            (unless (and (fixnump index) (< -1 index dim))
              (if invalid-index-error-p
                  (invalid-array-index-error array index dim axis)
                  (return-from %array-row-major-index nil)))
            (incf result (* chunk-size (the fixnum index)))
            (setf chunk-size (* chunk-size dim))))
        (let ((index (first subscripts))
              (length (length (the (simple-array * (*)) array))))
          (unless (and (fixnump index) (< -1 index length))
            (if invalid-index-error-p
                (invalid-array-index-error array index length)
                (return-from %array-row-major-index nil)))
          index))))

(defun array-in-bounds-p (array &rest subscripts)
  #!+sb-doc
  "Return T if the SUBSCRIPTS are in bounds for the ARRAY, NIL otherwise."
  (if (%array-row-major-index array subscripts nil)
      t))

(defun array-row-major-index (array &rest subscripts)
  (declare (truly-dynamic-extent subscripts))
  (%array-row-major-index array subscripts))

(defun aref (array &rest subscripts)
  #!+sb-doc
  "Return the element of the ARRAY specified by the SUBSCRIPTS."
  (declare (truly-dynamic-extent subscripts))
  (row-major-aref array (%array-row-major-index array subscripts)))

(defun %aset (array &rest stuff)
  (declare (truly-dynamic-extent stuff))
  (let ((subscripts (butlast stuff))
        (new-value (car (last stuff))))
    (setf (row-major-aref array (%array-row-major-index array subscripts))
          new-value)))

;;; FIXME: What's supposed to happen with functions
;;; like AREF when we (DEFUN (SETF FOO) ..) when
;;; DEFSETF FOO is also defined? It seems as though the logical
;;; thing to do would be to nuke the macro definition for (SETF FOO)
;;; and replace it with the (SETF FOO) function, issuing a warning,
;;; just as for ordinary functions
;;;  * (LISP-IMPLEMENTATION-VERSION)
;;;  "18a+ release x86-linux 2.4.7 6 November 1998 cvs"
;;;  * (DEFMACRO ZOO (X) `(+ ,X ,X))
;;;  ZOO
;;;  * (DEFUN ZOO (X) (* 3 X))
;;;  Warning: ZOO previously defined as a macro.
;;;  ZOO
;;; But that doesn't seem to be what happens in CMU CL.
;;;
;;; KLUDGE: this is probably because ANSI, in its wisdom (CLHS
;;; 5.1.2.5) requires implementations to support
;;;   (SETF (APPLY #'AREF ...) ...)
;;; [and also #'BIT and #'SBIT].  Yes, this is terrifying, and it's
;;; also terrifying that this sequence of definitions causes it to
;;; work.
;;;
;;; Also, it would be nice to make DESCRIBE FOO tell whether a symbol
;;; has a setf expansion and/or a setf function defined.

#!-sb-fluid (declaim (inline (setf aref)))
(defun (setf aref) (new-value array &rest subscripts)
  (declare (truly-dynamic-extent subscripts))
  (declare (type array array))
  (setf (row-major-aref array (%array-row-major-index array subscripts))
        new-value))

(defun row-major-aref (array index)
  #!+sb-doc
  "Return the element of array corressponding to the row-major index. This is
   SETF'able."
  (declare (optimize (safety 1)))
  (row-major-aref array index))

(defun %set-row-major-aref (array index new-value)
  (declare (optimize (safety 1)))
  (setf (row-major-aref array index) new-value))

(defun svref (simple-vector index)
  #!+sb-doc
  "Return the INDEX'th element of the given Simple-Vector."
  (declare (optimize (safety 1)))
  (aref simple-vector index))

(defun %svset (simple-vector index new)
  (declare (optimize (safety 1)))
  (setf (aref simple-vector index) new))

(defun bit (bit-array &rest subscripts)
  #!+sb-doc
  "Return the bit from the BIT-ARRAY at the specified SUBSCRIPTS."
  (declare (type (array bit) bit-array) (optimize (safety 1)))
  (row-major-aref bit-array (%array-row-major-index bit-array subscripts)))

(defun %bitset (bit-array &rest stuff)
  (declare (type (array bit) bit-array) (optimize (safety 1)))
  (let ((subscripts (butlast stuff))
        (new-value (car (last stuff))))
    (setf (row-major-aref bit-array
                          (%array-row-major-index bit-array subscripts))
          new-value)))

#!-sb-fluid (declaim (inline (setf bit)))
(defun (setf bit) (new-value bit-array &rest subscripts)
  (declare (type (array bit) bit-array) (optimize (safety 1)))
  (setf (row-major-aref bit-array
                        (%array-row-major-index bit-array subscripts))
        new-value))

(defun sbit (simple-bit-array &rest subscripts)
  #!+sb-doc
  "Return the bit from SIMPLE-BIT-ARRAY at the specified SUBSCRIPTS."
  (declare (type (simple-array bit) simple-bit-array) (optimize (safety 1)))
  (row-major-aref simple-bit-array
                  (%array-row-major-index simple-bit-array subscripts)))

;;; KLUDGE: Not all these things (%SET-ROW-MAJOR-AREF, %SET-FILL-POINTER,
;;; %SET-FDEFINITION, %SCHARSET, %SBITSET..) seem to deserve separate names.
;;; Could we just DEFUN (SETF SBIT) etc. and get rid of the non-ANSI names?
;;; -- WHN 19990911
(defun %sbitset (simple-bit-array &rest stuff)
  (declare (type (simple-array bit) simple-bit-array) (optimize (safety 1)))
  (let ((subscripts (butlast stuff))
        (new-value (car (last stuff))))
    (setf (row-major-aref simple-bit-array
                          (%array-row-major-index simple-bit-array subscripts))
          new-value)))

#!-sb-fluid (declaim (inline (setf sbit)))
(defun (setf sbit) (new-value bit-array &rest subscripts)
  (declare (type (simple-array bit) bit-array) (optimize (safety 1)))
  (setf (row-major-aref bit-array
                        (%array-row-major-index bit-array subscripts))
        new-value))

;;;; miscellaneous array properties

(defun array-element-type (array)
  #!+sb-doc
  "Return the type of the elements of the array"
  (let ((widetag (widetag-of array)))
    (macrolet ((pick-element-type (&rest stuff)
                 `(cond ,@(mapcar (lambda (stuff)
                                    (cons
                                     (let ((item (car stuff)))
                                       (cond ((eq item t)
                                              t)
                                             ((listp item)
                                              (cons 'or
                                                    (mapcar (lambda (x)
                                                              `(= widetag ,x))
                                                            item)))
                                             (t
                                              `(= widetag ,item))))
                                     (cdr stuff)))
                                  stuff))))
      #.`(pick-element-type
          ,@(map 'list
                 (lambda (saetp)
                   `(,(if (sb!vm:saetp-complex-typecode saetp)
                          (list (sb!vm:saetp-typecode saetp)
                                (sb!vm:saetp-complex-typecode saetp))
                          (sb!vm:saetp-typecode saetp))
                     ',(sb!vm:saetp-specifier saetp)))
                 sb!vm:*specialized-array-element-type-properties*)
          ((sb!vm:simple-array-widetag
            sb!vm:complex-vector-widetag
            sb!vm:complex-array-widetag)
           (with-array-data ((array array) (start) (end))
             (declare (ignore start end))
             (array-element-type array)))
          (t
           (error 'type-error :datum array :expected-type 'array))))))

(defun array-rank (array)
  #!+sb-doc
  "Return the number of dimensions of ARRAY."
  (if (array-header-p array)
      (%array-rank array)
      1))

(defun array-dimension (array axis-number)
  #!+sb-doc
  "Return the length of dimension AXIS-NUMBER of ARRAY."
  (declare (array array) (type index axis-number))
  (cond ((not (array-header-p array))
         (unless (= axis-number 0)
           (error "Vector axis is not zero: ~S" axis-number))
         (length (the (simple-array * (*)) array)))
        ((>= axis-number (%array-rank array))
         (error "Axis number ~W is too big; ~S only has ~D dimension~:P."
                axis-number array (%array-rank array)))
        (t
         (%array-dimension array axis-number))))

(defun array-dimensions (array)
  #!+sb-doc
  "Return a list whose elements are the dimensions of the array"
  (declare (array array))
  (if (array-header-p array)
      (do ((results nil (cons (array-dimension array index) results))
           (index (1- (array-rank array)) (1- index)))
          ((minusp index) results))
      (list (array-dimension array 0))))

(defun array-total-size (array)
  #!+sb-doc
  "Return the total number of elements in the Array."
  (declare (array array))
  (if (array-header-p array)
      (%array-available-elements array)
      (length (the vector array))))

(defun array-displacement (array)
  #!+sb-doc
  "Return the values of :DISPLACED-TO and :DISPLACED-INDEX-offset
   options to MAKE-ARRAY, or NIL and 0 if not a displaced array."
  (declare (type array array))
  (if (and (array-header-p array) ; if unsimple and
           (%array-displaced-p array)) ; displaced
      (values (%array-data-vector array) (%array-displacement array))
      (values nil 0)))

(defun adjustable-array-p (array)
  #!+sb-doc
  "Return T if (ADJUST-ARRAY ARRAY...) would return an array identical
   to the argument, this happens for complex arrays."
  (declare (array array))
  ;; Note that this appears not to be a fundamental limitation.
  ;; non-vector SIMPLE-ARRAYs are in fact capable of being adjusted,
  ;; but in practice we test using ADJUSTABLE-ARRAY-P in ADJUST-ARRAY.
  ;; -- CSR, 2004-03-01.
  (not (typep array 'simple-array)))

;;;; fill pointer frobbing stuff

(defun array-has-fill-pointer-p (array)
  #!+sb-doc
  "Return T if the given ARRAY has a fill pointer, or NIL otherwise."
  (declare (array array))
  (and (array-header-p array) (%array-fill-pointer-p array)))

(defun fill-pointer-error (vector arg)
  (cond (arg
         (aver (array-has-fill-pointer-p vector))
         (let ((max (%array-available-elements vector)))
           (error 'simple-type-error
                  :datum arg
                  :expected-type (list 'integer 0 max)
                  :format-control "The new fill pointer, ~S, is larger than the length of the vector (~S.)"
                  :format-arguments (list arg max))))
        (t
         (error 'simple-type-error
                :datum vector
                :expected-type '(and vector (satisfies array-has-fill-pointer-p))
                :format-control "~S is not an array with a fill pointer."
                :format-arguments (list vector)))))

(defun fill-pointer (vector)
  #!+sb-doc
  "Return the FILL-POINTER of the given VECTOR."
  (if (array-has-fill-pointer-p vector)
      (%array-fill-pointer vector)
      (fill-pointer-error vector nil)))

(defun %set-fill-pointer (vector new)
  (flet ((oops (x)
           (fill-pointer-error vector x)))
    (if (array-has-fill-pointer-p vector)
        (if (> new (%array-available-elements vector))
            (oops new)
            (setf (%array-fill-pointer vector) new))
        (oops nil))))

;;; FIXME: It'd probably make sense to use a MACROLET to share the
;;; guts of VECTOR-PUSH between VECTOR-PUSH-EXTEND. Such a macro
;;; should probably be based on the VECTOR-PUSH-EXTEND code (which is
;;; new ca. sbcl-0.7.0) rather than the VECTOR-PUSH code (which dates
;;; back to CMU CL).
(defun vector-push (new-el array)
  #!+sb-doc
  "Attempt to set the element of ARRAY designated by its fill pointer
   to NEW-EL, and increment the fill pointer by one. If the fill pointer is
   too large, NIL is returned, otherwise the index of the pushed element is
   returned."
  (declare (vector array))
  (let ((fill-pointer (fill-pointer array)))
    (declare (fixnum fill-pointer))
    (cond ((= fill-pointer (%array-available-elements array))
           nil)
          (t
           (locally (declare (optimize (safety 0)))
             (setf (aref array fill-pointer) new-el))
           (setf (%array-fill-pointer array) (1+ fill-pointer))
           fill-pointer))))

(defun vector-push-extend (new-element
                           vector
                           &optional
                           (min-extension
                            (let ((length (length vector)))
                              (min (1+ length)
                                   (- array-dimension-limit length)))))
  (declare (vector vector) (fixnum min-extension))
  (let ((fill-pointer (fill-pointer vector)))
    (declare (fixnum fill-pointer))
    (when (= fill-pointer (%array-available-elements vector))
      (adjust-array vector (+ fill-pointer (max 1 min-extension))))
    ;; disable bounds checking
    (locally (declare (optimize (safety 0)))
      (setf (aref vector fill-pointer) new-element))
    (setf (%array-fill-pointer vector) (1+ fill-pointer))
    fill-pointer))

(defun vector-pop (array)
  #!+sb-doc
  "Decrease the fill pointer by 1 and return the element pointed to by the
  new fill pointer."
  (declare (vector array))
  (let ((fill-pointer (fill-pointer array)))
    (declare (fixnum fill-pointer))
    (if (zerop fill-pointer)
        (error "There is nothing left to pop.")
        ;; disable bounds checking (and any fixnum test)
        (locally (declare (optimize (safety 0)))
          (aref array
                (setf (%array-fill-pointer array)
                      (1- fill-pointer)))))))


;;;; ADJUST-ARRAY

(defun adjust-array (array dimensions &key
                           (element-type (array-element-type array))
                           (initial-element nil initial-element-p)
                           (initial-contents nil initial-contents-p)
                           fill-pointer
                           displaced-to displaced-index-offset)
  #!+sb-doc
  "Adjust ARRAY's dimensions to the given DIMENSIONS and stuff."
  (when (invalid-array-p array)
    (invalid-array-error array))
  (let ((dimensions (if (listp dimensions) dimensions (list dimensions))))
    (cond ((/= (the fixnum (length (the list dimensions)))
               (the fixnum (array-rank array)))
           (error "The number of dimensions not equal to rank of array."))
          ((not (subtypep element-type (array-element-type array)))
           (error "The new element type, ~S, is incompatible with old type."
                  element-type))
          ((and fill-pointer (not (array-has-fill-pointer-p array)))
           (error 'type-error
                  :datum array
                  :expected-type '(satisfies array-has-fill-pointer-p))))
    (let ((array-rank (length (the list dimensions))))
      (declare (fixnum array-rank))
      (unless (= array-rank 1)
        (when fill-pointer
          (error "Only vectors can have fill pointers.")))
      (cond (initial-contents-p
             ;; array former contents replaced by INITIAL-CONTENTS
             (if (or initial-element-p displaced-to)
                 (error "INITIAL-CONTENTS may not be specified with ~
                         the :INITIAL-ELEMENT or :DISPLACED-TO option."))
             (let* ((array-size (apply #'* dimensions))
                    (array-data (data-vector-from-inits
                                 dimensions array-size element-type
                                 initial-contents initial-contents-p
                                 initial-element initial-element-p)))
               (if (adjustable-array-p array)
                   (set-array-header array array-data array-size
                                 (get-new-fill-pointer array array-size
                                                       fill-pointer)
                                 0 dimensions nil nil)
                   (if (array-header-p array)
                       ;; simple multidimensional or single dimensional array
                       (make-array dimensions
                                   :element-type element-type
                                   :initial-contents initial-contents)
                       array-data))))
            (displaced-to
             ;; We already established that no INITIAL-CONTENTS was supplied.
             (when initial-element
               (error "The :INITIAL-ELEMENT option may not be specified ~
                       with :DISPLACED-TO."))
             (unless (subtypep element-type (array-element-type displaced-to))
               (error "can't displace an array of type ~S into another of ~
                       type ~S"
                      element-type (array-element-type displaced-to)))
             (let ((displacement (or displaced-index-offset 0))
                   (array-size (apply #'* dimensions)))
               (declare (fixnum displacement array-size))
               (if (< (the fixnum (array-total-size displaced-to))
                      (the fixnum (+ displacement array-size)))
                   (error "The :DISPLACED-TO array is too small."))
               (if (adjustable-array-p array)
                   ;; None of the original contents appear in adjusted array.
                   (set-array-header array displaced-to array-size
                                     (get-new-fill-pointer array array-size
                                                           fill-pointer)
                                     displacement dimensions t nil)
                   ;; simple multidimensional or single dimensional array
                   (make-array dimensions
                               :element-type element-type
                               :displaced-to displaced-to
                               :displaced-index-offset
                               displaced-index-offset))))
            ((= array-rank 1)
             (let ((old-length (array-total-size array))
                   (new-length (car dimensions))
                   new-data)
               (declare (fixnum old-length new-length))
               (with-array-data ((old-data array) (old-start)
                                 (old-end old-length))
                 (cond ((or (and (array-header-p array)
                                 (%array-displaced-p array))
                            (< old-length new-length))
                        (setf new-data
                              (data-vector-from-inits
                               dimensions new-length element-type
                               initial-contents initial-contents-p
                               initial-element initial-element-p))
                        (replace new-data old-data
                                 :start2 old-start :end2 old-end))
                       (t (setf new-data
                                (shrink-vector old-data new-length))))
                 (if (adjustable-array-p array)
                     (set-array-header array new-data new-length
                                       (get-new-fill-pointer array new-length
                                                             fill-pointer)
                                       0 dimensions nil nil)
                     new-data))))
            (t
             (let ((old-length (%array-available-elements array))
                   (new-length (apply #'* dimensions)))
               (declare (fixnum old-length new-length))
               (with-array-data ((old-data array) (old-start)
                                 (old-end old-length))
                 (declare (ignore old-end))
                 (let ((new-data (if (or (and (array-header-p array)
                                              (%array-displaced-p array))
                                         (> new-length old-length))
                                     (data-vector-from-inits
                                      dimensions new-length
                                      element-type () nil
                                      initial-element initial-element-p)
                                     old-data)))
                   (if (or (zerop old-length) (zerop new-length))
                       (when initial-element-p (fill new-data initial-element))
                       (zap-array-data old-data (array-dimensions array)
                                       old-start
                                       new-data dimensions new-length
                                       element-type initial-element
                                       initial-element-p))
                   (if (adjustable-array-p array)
                       (set-array-header array new-data new-length
                                         nil 0 dimensions nil nil)
                       (let ((new-array
                              (make-array-header
                               sb!vm:simple-array-widetag array-rank)))
                         (set-array-header new-array new-data new-length
                                           nil 0 dimensions nil t)))))))))))


(defun get-new-fill-pointer (old-array new-array-size fill-pointer)
  (cond ((not fill-pointer)
         (when (array-has-fill-pointer-p old-array)
           (when (> (%array-fill-pointer old-array) new-array-size)
             (error "cannot ADJUST-ARRAY an array (~S) to a size (~S) that is ~
                     smaller than its fill pointer (~S)"
                    old-array new-array-size (fill-pointer old-array)))
           (%array-fill-pointer old-array)))
        ((not (array-has-fill-pointer-p old-array))
         (error "cannot supply a non-NIL value (~S) for :FILL-POINTER ~
                 in ADJUST-ARRAY unless the array (~S) was originally ~
                 created with a fill pointer"
                fill-pointer
                old-array))
        ((numberp fill-pointer)
         (when (> fill-pointer new-array-size)
           (error "can't supply a value for :FILL-POINTER (~S) that is larger ~
                   than the new length of the vector (~S)"
                  fill-pointer new-array-size))
         fill-pointer)
        ((eq fill-pointer t)
         new-array-size)
        (t
         (error "bogus value for :FILL-POINTER in ADJUST-ARRAY: ~S"
                fill-pointer))))

;;; Destructively alter VECTOR, changing its length to NEW-LENGTH,
;;; which must be less than or equal to its current length. This can
;;; be called on vectors without a fill pointer but it is extremely
;;; dangerous to do so: shrinking the size of an object (as viewed by
;;; the gc) makes bounds checking unreliable in the face of interrupts
;;; or multi-threading. Call it only on provably local vectors.
(defun %shrink-vector (vector new-length)
  (declare (vector vector))
  (unless (array-header-p vector)
    (macrolet ((frob (name &rest things)
                 `(etypecase ,name
                    ((simple-array nil (*)) (error 'nil-array-accessed-error))
                    ,@(mapcar (lambda (thing)
                                (destructuring-bind (type-spec fill-value)
                                    thing
                                  `(,type-spec
                                    (fill (truly-the ,type-spec ,name)
                                          ,fill-value
                                          :start new-length))))
                              things))))
      ;; Set the 'tail' of the vector to the appropriate type of zero,
      ;; "because in some cases we'll scavenge larger areas in one go,
      ;; like groups of pages that had triggered the write barrier, or
      ;; the whole static space" according to jsnell.
      #.`(frob vector
          ,@(map 'list
                 (lambda (saetp)
                   `((simple-array ,(sb!vm:saetp-specifier saetp) (*))
                     ,(if (or (eq (sb!vm:saetp-specifier saetp) 'character)
                              #!+sb-unicode
                              (eq (sb!vm:saetp-specifier saetp) 'base-char))
                          *default-init-char-form*
                          (sb!vm:saetp-initial-element-default saetp))))
                 (remove-if-not
                  #'sb!vm:saetp-specifier
                  sb!vm:*specialized-array-element-type-properties*)))))
  ;; Only arrays have fill-pointers, but vectors have their length
  ;; parameter in the same place.
  (setf (%array-fill-pointer vector) new-length)
  vector)

(defun shrink-vector (vector new-length)
  (declare (vector vector))
  (cond
    ((eq (length vector) new-length)
     vector)
    ((array-has-fill-pointer-p vector)
     (setf (%array-fill-pointer vector) new-length)
     vector)
    (t (subseq vector 0 new-length))))

;;; BIG THREAD SAFETY NOTE
;;;
;;; ADJUST-ARRAY/SET-ARRAY-HEADER, and its callees are very
;;; thread unsafe. They are nonatomic, and can mess with parallel
;;; code using the same arrays.
;;;
;;; A likely seeming fix is an additional level of indirection:
;;; ARRAY-HEADER -> ARRAY-INFO -> ... where ARRAY-HEADER would
;;; hold nothing but the pointer to ARRAY-INFO, and ARRAY-INFO
;;; would hold everything ARRAY-HEADER now holds. This allows
;;; consing up a new ARRAY-INFO and replacing it atomically in
;;; the ARRAY-HEADER.
;;;
;;; %WALK-DISPLACED-ARRAY-BACKPOINTERS is an especially nasty
;;; one: not only is it needed extremely rarely, which makes
;;; any thread safety bugs involving it look like rare random
;;; corruption, but because it walks the chain *upwards*, which
;;; may violate user expectations.

(defun %save-displaced-array-backpointer (array data)
  (flet ((purge (pointers)
           (remove-if (lambda (value)
                        (or (not value) (eq array value)))
                      pointers
                      :key #'weak-pointer-value)))
    ;; Add backpointer to the new data vector if it has a header.
    (when (array-header-p data)
      (setf (%array-displaced-from data)
            (cons (make-weak-pointer array)
                  (purge (%array-displaced-from data)))))
    ;; Remove old backpointer, if any.
    (let ((old-data (%array-data-vector array)))
      (when (and (neq data old-data) (array-header-p old-data))
        (setf (%array-displaced-from old-data)
              (purge (%array-displaced-from old-data)))))))

(defun %walk-displaced-array-backpointers (array new-length)
  (dolist (p (%array-displaced-from array))
    (let ((from (weak-pointer-value p)))
      (when (and from (eq array (%array-data-vector from)))
        (let ((requires (+ (%array-available-elements from)
                           (%array-displacement from))))
          (unless (>= new-length requires)
            ;; ANSI sayeth (ADJUST-ARRAY dictionary entry):
            ;;
            ;;   "If A is displaced to B, the consequences are unspecified if B is
            ;;   adjusted in such a way that it no longer has enough elements to
            ;;   satisfy A.
            ;;
            ;; since we're hanging on a weak pointer here, we can't signal an
            ;; error right now: the array that we're looking at might be
            ;; garbage. Instead, we set all dimensions to zero so that next
            ;; safe access to the displaced array will trap. Additionally, we
            ;; save the original dimensions, so we can signal a more
            ;; understandable error when the time comes.
            (%walk-displaced-array-backpointers from 0)
            (setf (%array-fill-pointer from) 0
                  (%array-available-elements from) 0
                  (%array-displaced-p from) (array-dimensions array))
            (dotimes (i (%array-rank from))
              (setf (%array-dimension from i) 0))))))))

;;; Fill in array header with the provided information, and return the array.
(defun set-array-header (array data length fill-pointer displacement dimensions
                         displacedp newp)
  (if newp
      (setf (%array-displaced-from array) nil)
      (%walk-displaced-array-backpointers array length))
  (when displacedp
    (%save-displaced-array-backpointer array data))
  (setf (%array-data-vector array) data)
  (setf (%array-available-elements array) length)
  (cond (fill-pointer
         (setf (%array-fill-pointer array) fill-pointer)
         (setf (%array-fill-pointer-p array) t))
        (t
         (setf (%array-fill-pointer array) length)
         (setf (%array-fill-pointer-p array) nil)))
  (setf (%array-displacement array) displacement)
  (if (listp dimensions)
      (dotimes (axis (array-rank array))
        (declare (type index axis))
        (setf (%array-dimension array axis) (pop dimensions)))
      (setf (%array-dimension array 0) dimensions))
  (setf (%array-displaced-p array) displacedp)
  array)

;;; User visible extension
(declaim (ftype (function (array) (values (simple-array * (*)) &optional))
                array-storage-vector))
(defun array-storage-vector (array)
  "Returns the underlying storage vector of ARRAY, which must be a non-displaced array.

In SBCL, if ARRAY is a of type \(SIMPLE-ARRAY * \(*)), it is its own storage
vector. Multidimensional arrays, arrays with fill pointers, and adjustable
arrays have an underlying storage vector with the same ARRAY-ELEMENT-TYPE as
ARRAY, which this function returns.

Important note: the underlying vector is an implementation detail. Even though
this function exposes it, changes in the implementation may cause this
function to be removed without further warning."
  ;; KLUDGE: Without TRULY-THE the system is not smart enough to figure out that
  ;; the return value is always of the known type.
  (truly-the (simple-array * (*))
             (if (array-header-p array)
                 (if (%array-displaced-p array)
                     (error "~S cannot be used with displaced arrays. Use ~S instead."
                            'array-storage-vector 'array-displacement)
                     (%array-data-vector array))
                 array)))


;;;; ZAP-ARRAY-DATA for ADJUST-ARRAY

;;; This does the grinding work for ADJUST-ARRAY. It zaps the data
;;; from the OLD-DATA in an arrangement specified by the OLD-DIMS to
;;; the NEW-DATA in an arrangement specified by the NEW-DIMS. OFFSET
;;; is a displaced offset to be added to computed indices of OLD-DATA.
(defun zap-array-data (old-data old-dims offset new-data new-dims new-length
                       element-type initial-element initial-element-p)
  (declare (list old-dims new-dims)
           (fixnum new-length))
  ;; OLD-DIMS comes from array-dimensions, which returns a fresh list
  ;; at least in SBCL.
  ;; NEW-DIMS comes from the user.
  (setf old-dims (nreverse old-dims)
        new-dims (reverse new-dims))
  (cond ((eq old-data new-data)
         ;; NEW-LENGTH, ELEMENT-TYPE, INITIAL-ELEMENT, and
         ;; INITIAL-ELEMENT-P are used when OLD-DATA and NEW-DATA are
         ;; EQ; in this case, a temporary must be used and filled
         ;; appropriately. specified initial-element.
         (when initial-element-p
           ;; FIXME: transforming this TYPEP to someting a bit faster
           ;; would be a win...
           (unless (typep initial-element element-type)
             (error "~S can't be used to initialize an array of type ~S."
                    initial-element element-type)))
         (let ((temp (if initial-element-p
                         (make-array new-length :initial-element initial-element)
                         (make-array new-length))))
           (declare (simple-vector temp))
           (zap-array-data-aux old-data old-dims offset temp new-dims)
           (dotimes (i new-length)
             (setf (aref new-data i) (aref temp i)))
           ;; Kill the temporary vector to prevent garbage retention.
           (%shrink-vector temp 0)))
        (t
         ;; When OLD-DATA and NEW-DATA are not EQ, NEW-DATA has
         ;; already been filled with any
         (zap-array-data-aux old-data old-dims offset new-data new-dims))))

(defun zap-array-data-aux (old-data old-dims offset new-data new-dims)
  (declare (fixnum offset))
  (let ((limits (mapcar (lambda (x y)
                          (declare (fixnum x y))
                          (1- (the fixnum (min x y))))
                        old-dims new-dims)))
    (macrolet ((bump-index-list (index limits)
                 `(do ((subscripts ,index (cdr subscripts))
                       (limits ,limits (cdr limits)))
                      ((null subscripts) :eof)
                    (cond ((< (the fixnum (car subscripts))
                              (the fixnum (car limits)))
                           (rplaca subscripts
                                   (1+ (the fixnum (car subscripts))))
                           (return ,index))
                          (t (rplaca subscripts 0))))))
      (do ((index (make-list (length old-dims) :initial-element 0)
                  (bump-index-list index limits)))
          ((eq index :eof))
        (setf (aref new-data (row-major-index-from-dims index new-dims))
              (aref old-data
                    (+ (the fixnum (row-major-index-from-dims index old-dims))
                       offset)))))))

;;; Figure out the row-major-order index of an array reference from a
;;; list of subscripts and a list of dimensions. This is for internal
;;; calls only, and the subscripts and dim-list variables are assumed
;;; to be reversed from what the user supplied.
(defun row-major-index-from-dims (rev-subscripts rev-dim-list)
  (do ((rev-subscripts rev-subscripts (cdr rev-subscripts))
       (rev-dim-list rev-dim-list (cdr rev-dim-list))
       (chunk-size 1)
       (result 0))
      ((null rev-dim-list) result)
    (declare (fixnum chunk-size result))
    (setq result (+ result
                    (the fixnum (* (the fixnum (car rev-subscripts))
                                   chunk-size))))
    (setq chunk-size (* chunk-size (the fixnum (car rev-dim-list))))))

;;;; some bit stuff

(defun bit-array-same-dimensions-p (array1 array2)
  (declare (type (array bit) array1 array2))
  (and (= (array-rank array1)
          (array-rank array2))
       (dotimes (index (array-rank array1) t)
         (when (/= (array-dimension array1 index)
                   (array-dimension array2 index))
           (return nil)))))

(defun pick-result-array (result-bit-array bit-array-1)
  (case result-bit-array
    ((t) bit-array-1)
    ((nil) (make-array (array-dimensions bit-array-1)
                       :element-type 'bit
                       :initial-element 0))
    (t
     (unless (bit-array-same-dimensions-p bit-array-1
                                          result-bit-array)
       (error "~S and ~S don't have the same dimensions."
              bit-array-1 result-bit-array))
     result-bit-array)))

(defmacro def-bit-array-op (name function)
  `(defun ,name (bit-array-1 bit-array-2 &optional result-bit-array)
     #!+sb-doc
     ,(format nil
              "Perform a bit-wise ~A on the elements of BIT-ARRAY-1 and ~
               BIT-ARRAY-2,~%  putting the results in RESULT-BIT-ARRAY. ~
               If RESULT-BIT-ARRAY is T,~%  BIT-ARRAY-1 is used. If ~
               RESULT-BIT-ARRAY is NIL or omitted, a new array is~%  created. ~
               All the arrays must have the same rank and dimensions."
              (symbol-name function))
     (declare (type (array bit) bit-array-1 bit-array-2)
              (type (or (array bit) (member t nil)) result-bit-array))
     (unless (bit-array-same-dimensions-p bit-array-1 bit-array-2)
       (error "~S and ~S don't have the same dimensions."
              bit-array-1 bit-array-2))
     (let ((result-bit-array (pick-result-array result-bit-array bit-array-1)))
       (if (and (simple-bit-vector-p bit-array-1)
                (simple-bit-vector-p bit-array-2)
                (simple-bit-vector-p result-bit-array))
           (locally (declare (optimize (speed 3) (safety 0)))
             (,name bit-array-1 bit-array-2 result-bit-array))
           (with-array-data ((data1 bit-array-1) (start1) (end1))
             (declare (ignore end1))
             (with-array-data ((data2 bit-array-2) (start2) (end2))
               (declare (ignore end2))
               (with-array-data ((data3 result-bit-array) (start3) (end3))
                 (do ((index-1 start1 (1+ index-1))
                      (index-2 start2 (1+ index-2))
                      (index-3 start3 (1+ index-3)))
                     ((>= index-3 end3) result-bit-array)
                   (declare (type index index-1 index-2 index-3))
                   (setf (sbit data3 index-3)
                         (logand (,function (sbit data1 index-1)
                                            (sbit data2 index-2))
                                 1))))))))))

(def-bit-array-op bit-and logand)
(def-bit-array-op bit-ior logior)
(def-bit-array-op bit-xor logxor)
(def-bit-array-op bit-eqv logeqv)
(def-bit-array-op bit-nand lognand)
(def-bit-array-op bit-nor lognor)
(def-bit-array-op bit-andc1 logandc1)
(def-bit-array-op bit-andc2 logandc2)
(def-bit-array-op bit-orc1 logorc1)
(def-bit-array-op bit-orc2 logorc2)

(defun bit-not (bit-array &optional result-bit-array)
  #!+sb-doc
  "Performs a bit-wise logical NOT on the elements of BIT-ARRAY,
  putting the results in RESULT-BIT-ARRAY. If RESULT-BIT-ARRAY is T,
  BIT-ARRAY is used. If RESULT-BIT-ARRAY is NIL or omitted, a new array is
  created. Both arrays must have the same rank and dimensions."
  (declare (type (array bit) bit-array)
           (type (or (array bit) (member t nil)) result-bit-array))
  (let ((result-bit-array (pick-result-array result-bit-array bit-array)))
    (if (and (simple-bit-vector-p bit-array)
             (simple-bit-vector-p result-bit-array))
        (locally (declare (optimize (speed 3) (safety 0)))
          (bit-not bit-array result-bit-array))
        (with-array-data ((src bit-array) (src-start) (src-end))
          (declare (ignore src-end))
          (with-array-data ((dst result-bit-array) (dst-start) (dst-end))
            (do ((src-index src-start (1+ src-index))
                 (dst-index dst-start (1+ dst-index)))
                ((>= dst-index dst-end) result-bit-array)
              (declare (type index src-index dst-index))
              (setf (sbit dst dst-index)
                    (logxor (sbit src src-index) 1))))))))