Commit e772ce37 authored by rtoy's avatar rtoy
Browse files

Fix critical bug in ENDIAN-SWAP-VECTOR. When swapping nibbles, pairs 

of bits or bits, the loop was counting over element indices but the
body was accessing by bytes.  This was overwriting stuff outside the
array.  Fix by adjusting indices to count by bytes.
parent eca0176a

code/stream-vector-io.lisp

+45 −29
Original line number Diff line number Diff line
@@ -5,7 +5,7 @@ 
;;; Carnegie Mellon University, and has been placed in the public domain.

;;;

(ext:file-comment

  "$Header: /Volumes/share2/src/cmucl/cvs2git/cvsroot/src/code/stream-vector-io.lisp,v 1.3.6.6 2009/06/02 18:26:33 rtoy Exp $")

  "$Header: /Volumes/share2/src/cmucl/cvs2git/cvsroot/src/code/stream-vector-io.lisp,v 1.3.6.7 2009/06/03 15:50:12 rtoy Exp $")

;;;

;;; **********************************************************************

;;;
@@ -80,14 +80,19 @@ 
				     endian-swap))

	  (-1

	   ;; Swap nibbles

	   (loop for i fixnum from start below end

	   ;; NOTE:  start and end are in terms of elements (4 bits)  but we want octets in this loop.

	   (let ((start-octet (truncate start 2))

		 (end-octet (truncate end 2)))

	     (loop for i fixnum from start-octet below end-octet

		   do

		   (let ((x (bref data i)))

		     (setf (bref data i) (logior (ash (logand x #x0f) 4)

					       (ash (logand x #xf0) -4))))))

						 (ash (logand x #xf0) -4)))))))

	  (-2

	   ;; Swap pairs

	   (loop for i fixnum from start below end

	   ;; Swap pairs of bits.

	   (let ((start-octet (truncate start 4))

		 (end-octet (truncate end 4)))

	     (loop for i fixnum from start-octet below end-octet

		   do

		   (let ((x (bref data i)))

		     (declare (type (unsigned-byte 8) x))
@@ -95,9 +100,11 @@ 
				     (ash (logand x #xcc) -2)))

		     (setf x (logior (ash (logand x #x0f) 4)

				     (ash (logand x #xf0) -4)))

		   (setf (bref data i) x))))

		     (setf (bref data i) x)))))

	  (-8

	   ;; Swap bits

	   (let ((start-octet (truncate start 8))

		 (end-octet (truncate end 8)))

	     (loop for i fixnum from start below end

		   do

		   (let ((x (bref data i)))
@@ -108,7 +115,7 @@ 
				     (ash (logand x #xcc) -2)))

		     (setf x (logior (ash (logand x #x0f) 4)

				     (ash (logand x #xf0) -4)))

		   (setf (bref data i) x))))

		     (setf (bref data i) x)))))

	  ;;otherwise, do nothing ???

	  )))))
@@ -142,6 +149,7 @@ 
			      (return (- numbytes need)))

			     (t (incf offset n)))))))

	     (read-n-x8-bytes (stream data offset-start offset-end byte-size)

	       (format t "~&read-n-x8-bytes:  offset start, end = ~A ~A~%" offset-start offset-end)

	       (let* ((x8-mult (truncate byte-size 8))

		      (numbytes (* (- offset-end offset-start) x8-mult))

		      (bytes-read (get-n-bytes
@@ -149,6 +157,7 @@ 
				   data

				   offset-start

				   numbytes)))

		 (format t "  numbytes = ~A~%" numbytes)

		 ;; A check should probably be made here in order to

		 ;; be sure that we actually read the right amount

		 ;; of bytes. (I.e. (truncate bytes-read x8-mult)
@@ -185,13 +194,20 @@ 
    (error "Wrong vector type ~a for read-vector on stream ~a." (type-of vector) stream))

  (let* ((octets-per-element (vector-elt-width vector))

	 (start-elt (truncate start octets-per-element))

	 (end-octet (or end (truncate (* (length vector) octets-per-element))))

	 (end-octet (or end (ceiling (* (length vector) octets-per-element))))

	 (end-elt  (if end

		       (truncate end octets-per-element)

		       (length vector)))

	 (next-index (read-vector* vector stream

				   start

				   end-octet)))

    (format t "~&read-vector: ~%")

    (format t "   end = ~A~%" end)

    (format t "   len = ~A~%" (length vector))

    (format t "   ope = ~A~%" octets-per-element)

    (format t "   start-elt = ~A~%" start-elt)

    (format t "   end-octet = ~A~%" end-octet)

    (format t "   end-elt   = ~A~%" end-elt)

    (endian-swap-vector vector start-elt end-elt

			(endian-swap-value vector endian-swap))

    next-index))
@@ -221,7 +237,7 @@ 


  (let* ((octets-per-element (vector-elt-width vector))

	 (start-elt (truncate start octets-per-element))

	 (end-octet (or end (truncate (* (length vector) octets-per-element))))

	 (end-octet (or end (ceiling (* (length vector) octets-per-element))))

	 (end-elt (if end

		      (truncate end octets-per-element)

		      (length vector)))