diff --git a/md5.lisp b/md5.lisp
index 10c95e4..b6f4ed5 100644
--- a/md5.lisp
+++ b/md5.lisp
@@ -1,16 +1,20 @@
 (defpackage :MD5 (:use :CL)
-  (:export #:+md5-magic-a+ #:+md5-magic-b+ #:+md5-magic-c+ #:+md5-magic-d+
-	   ;; Low-Level functions
-	   #:md5sum-update #:md5sum-final #:md5sum-checksum
-	   ;; Low-Level functions on character buffers
-	   #:md5sum-update-char #:md5sum-final-char
-	   ;; Mid-Level functions
-	   #:make-md5-state #:update-md5-state #:finalize-md5-state
-	   ;; High-Level functions on streams/files
-	   #:md5sum-char-stream #:md5sum-byte-stream #:md5sum-file))
+  (:export
+   ;; Low-Level types and functions
+   #:md5-regs #:initial-md5-regs #:md5regs-checksum
+   #:update-md5-block #:fill-block #:fill-block-ub8 #:fill-block-char
+   ;; Mid-Level types and functions
+   #:md5-state #:md5-state-p #:make-md5-state
+   #:update-md5-state #:finalize-md5-state
+   ;; High-Level functions on streams/files
+   #:md5sum-stream #:md5sum-file))
 
 (in-package :MD5)
 
+(eval-when (:compile-toplevel)
+  (defparameter *old-expansion-limit* ext:*inline-expansion-limit*)
+  (setq ext:*inline-expansion-limit* (max ext:*inline-expansion-limit* 1000)))
+
 ;;; Section 3.4:  Auxilliary functions
 
 (deftype ub32 () `(unsigned-byte 32))
@@ -84,12 +88,45 @@
 	finally
 	(return `(progn ,@result))))
 
-(defun update-md5-block (a b c d block)
-  (declare (type ub32 a b c d)
+;; Block-level operations
+
+(deftype md5-regs () `(simple-array (unsigned-byte 32) (4)))
+
+(defmacro md5-regs-a (regs)
+  `(aref ,regs 0))
+
+(defmacro md5-regs-b (regs)
+  `(aref ,regs 1))
+
+(defmacro md5-regs-c (regs)
+  `(aref ,regs 2))
+
+(defmacro md5-regs-d (regs)
+  `(aref ,regs 3))
+
+(defconstant +md5-magic-a+ #x67452301)
+(defconstant +md5-magic-b+ #xefcdab89)
+(defconstant +md5-magic-c+ #x98badcfe)
+(defconstant +md5-magic-d+ #x10325476)
+
+(declaim (inline initial-md5-regs))
+(defun initial-md5-regs ()
+  (declare (optimize (speed 3) (safety 0) (space 0) (debug 0)))
+  (let ((regs (make-array 4 :element-type '(unsigned-byte 32))))
+    (declare (type md5-regs regs))
+    (setf (md5-regs-a regs) +md5-magic-a+
+	  (md5-regs-b regs) +md5-magic-b+
+	  (md5-regs-c regs) +md5-magic-c+
+	  (md5-regs-d regs) +md5-magic-d+)
+    regs))
+
+(defun update-md5-block (regs block)
+  (declare (type md5-regs regs)
 	   (type (simple-array ub32 (16)) block)
 	   (optimize (speed 3) (safety 0) (space 0) (debug 0)))
-  (let ((old-a a) (old-b b) (old-c c) (old-d d))
-    (declare (type ub32 old-a old-b old-c old-d))
+  (let ((a (md5-regs-a regs)) (b (md5-regs-b regs))
+	(c (md5-regs-c regs)) (d (md5-regs-d regs)))
+    (declare (type ub32 a b c d))
     ;; Round 1
     (with-md5-round (f block)
       (A B C D  0  7  1)(D A B C  1 12  2)(C D A B  2 17  3)(B C D A  3 22  4)
@@ -115,21 +152,31 @@
       (A B C D  8  6 57)(D A B C 15 10 58)(C D A B  6 15 59)(B C D A 13 21 60)
       (A B C D  4  6 61)(D A B C 11 10 62)(C D A B  2 15 63)(B C D A  9 21 64))
     ;; Update and return
-    (values
-     (mod32+ old-a a)
-     (mod32+ old-b b)
-     (mod32+ old-c c)
-     (mod32+ old-d d))))
+    (setf (md5-regs-a regs) (mod32+ (md5-regs-a regs) a)
+	  (md5-regs-b regs) (mod32+ (md5-regs-b regs) b)
+	  (md5-regs-c regs) (mod32+ (md5-regs-c regs) c)
+	  (md5-regs-d regs) (mod32+ (md5-regs-d regs) d))
+    regs))
 
-(defconstant +md5-magic-a+ #x67452301)
-(defconstant +md5-magic-b+ #xefcdab89)
-(defconstant +md5-magic-c+ #x98badcfe)
-(defconstant +md5-magic-d+ #x10325476)
-
-;; Low-level drivers
-
-(declaim (inline fill-block fill-block-char))
+(declaim (inline fill-block fill-block-ub8 fill-block-char))
 (defun fill-block (block buffer offset)
+  (declare (type (integer 0 #.(- most-positive-fixnum 64)) offset)
+	   (type (simple-array ub32 (16)) block)
+	   (type (simple-array * (*)) buffer)
+	   (optimize (speed 3) (safety 0) (space 0) (debug 0)))
+  #+(and cmu x86)
+  (kernel:bit-bash-copy
+   buffer (+ (* vm:vector-data-offset vm:word-bits) (* offset vm:byte-bits))
+   block (* vm:vector-data-offset vm:word-bits)
+   (* 64 vm:byte-bits))
+  #-(and cmu x86)
+  (etypecase buffer
+    ((simple-array (unsigned-byte 8) (*))
+     (fill-block-ub8 block buffer offset))
+    (simple-string
+     (fill-block-char block buffer offset))))
+  
+(defun fill-block-ub8 (block buffer offset)
   (declare (type (integer 0 #.(- most-positive-fixnum 64)) offset)
 	   (type (simple-array ub32 (16)) block)
 	   (type (simple-array (unsigned-byte 8) (*)) buffer)
@@ -153,12 +200,7 @@
 			       (aref buffer (+ j 2)) 16)
 			      (kernel:shift-towards-end
 			       (aref buffer (+ j 1)) 8)
-			      (aref buffer j)))
-	      #+NIL
-	      (dpb (aref buffer (+ j 3)) (byte 8 24)
-		   (dpb (aref buffer (+ j 2)) (byte 8 16)
-			(dpb (aref buffer (+ j 1)) (byte 8 8)
-			     (aref buffer j)))))))
+			      (aref buffer j))))))
 
 (defun fill-block-char (block buffer offset)
   (declare (type (integer 0 #.(- most-positive-fixnum 64)) offset)
@@ -186,107 +228,32 @@
 			       (char-code (schar buffer (+ j 1))) 8)
 			      (char-code (schar buffer j)))))))
 
-(declaim (inline md5sum-update md5sum-final
-		 md5sum-update-char md5sum-final-char))
-(defun md5sum-update (a b c d block buffer offset)
+(declaim (inline md5regs-checksum))
+(defun md5regs-checksum (regs)
   (declare (optimize (speed 3) (safety 0) (space 0) (debug 0))
-	   (type ub32 a b c d)
-	   (type (integer 0 #.(- most-positive-fixnum 64)) offset)
-	   (type (simple-array ub32 (16)) block)
-	   (type (simple-array (unsigned-byte 8) (*)) buffer))
-  (fill-block block buffer offset)
-  (update-md5-block a b c d block))
-
-(defun md5sum-final (a b c d block buffer offset bytes total-length)
-  (declare (optimize (speed 3) (safety 0) (space 0) (debug 0))
-	   (type ub32 a b c d)
-	   (type (unsigned-byte 29) total-length)
-	   (type (integer 0 #.(- most-positive-fixnum 64)) offset)
-	   (type (integer 0 63) bytes)
-	   (type (simple-array ub32 (16)) block)
-	   (type (simple-array (unsigned-byte 8) (*)) buffer))
-  (setf (aref buffer (+ offset bytes)) #x80)
-  (loop for index of-type (integer 0 #.most-positive-fixnum)
-	from (+ offset bytes 1) to (+ offset 63)
-	do (setf (aref buffer index) #x00))
-  (fill-block block buffer offset)
-  (when (< bytes 56)
-    (setf (aref block 14) (* total-length 8)))
-  (multiple-value-bind (a b c d)
-      (update-md5-block a b c d block)
-    (if (< 56 bytes 64)
-	(progn
-	  (loop for index of-type (integer 0 16) from 0 to 15
-		do (setf (aref block index) #x00000000))
-	  (setf (aref block 14) (* total-length 8))
-	  (update-md5-block a b c d block))
-	(values a b c d))))
-
-(defun md5sum-update-char (a b c d block buffer offset)
-  (declare (optimize (speed 3) (safety 0) (space 0) (debug 0))
-	   (type ub32 a b c d)
-	   (type (integer 0 #.(- most-positive-fixnum 64)) offset)
-	   (type (simple-array ub32 (16)) block)
-	   (type simple-string buffer))
-  (fill-block-char block buffer offset)
-  (update-md5-block a b c d block))
-
-(defun md5sum-final-char (a b c d block buffer offset bytes total-length)
-  (declare (optimize (speed 3) (safety 0) (space 0) (debug 0))
-	   (type ub32 a b c d)
-	   (type (unsigned-byte 29) total-length)
-	   (type (integer 0 #.(- most-positive-fixnum 64)) offset)
-	   (type (integer 0 63) bytes)
-	   (type (simple-array ub32 (16)) block)
-	   (type simple-string buffer))
-  (setf (schar buffer (+ offset bytes)) (code-char #x80))
-  (loop for index of-type (integer 0 #.most-positive-fixnum)
-	from (+ offset bytes 1) to (+ offset 63)
-	do (setf (schar buffer index) (code-char #x00)))
-  (fill-block-char block buffer offset)
-  (when (< bytes 56)
-    (setf (aref block 14) (* total-length 8)))
-  (multiple-value-bind (a b c d)
-      (update-md5-block a b c d block)
-    (if (< 56 bytes 64)
-	(progn
-	  (loop for index of-type (integer 0 16) from 0 to 15
-		do (setf (aref block index) #x00000000))
-	  (setf (aref block 14) (* total-length 8))
-	  (update-md5-block a b c d block))
-	(values a b c d))))
-
-(defun md5sum-checksum (a b c d)
-  (declare (optimize (speed 3) (safety 0) (space 0) (debug 0))
-	   (type ub32 a b c d))
-  (make-array 16 :element-type '(unsigned-byte 8)
-	      :initial-contents
-	      (list
-	       (ldb (byte 8 0) a)
-	       (ldb (byte 8 8) a)
-	       (ldb (byte 8 16) a)
-	       (ldb (byte 8 24) a)
-	       (ldb (byte 8 0) b)
-	       (ldb (byte 8 8) b)
-	       (ldb (byte 8 16) b)
-	       (ldb (byte 8 24) b)
-	       (ldb (byte 8 0) c)
-	       (ldb (byte 8 8) c)
-	       (ldb (byte 8 16) c)
-	       (ldb (byte 8 24) c)
-	       (ldb (byte 8 0) d)
-	       (ldb (byte 8 8) d)
-	       (ldb (byte 8 16) d)
-	       (ldb (byte 8 24) d))))
+	   (type md5-regs regs))
+  (let ((result (make-array 16 :element-type '(unsigned-byte 8))))
+    (declare (type (simple-array (unsigned-byte 8) (16)) result))
+    (macrolet ((frob (reg offset)
+		 (let ((var (gensym)))
+		   `(let ((,var ,reg))
+		      (declare (type ub32 ,var))
+		      (setf
+		       (aref result ,offset) (ldb (byte 8 0) ,var)
+		       (aref result ,(+ offset 1)) (ldb (byte 8 8) ,var)
+		       (aref result ,(+ offset 2)) (ldb (byte 8 16) ,var)
+		       (aref result ,(+ offset 3)) (ldb (byte 8 24) ,var))))))
+      (frob (md5-regs-a regs) 0)
+      (frob (md5-regs-b regs) 4)
+      (frob (md5-regs-c regs) 8)
+      (frob (md5-regs-d regs) 12))
+    result))
 
 ;; Mid-Level Drivers
 
 (defstruct (md5-state
 	     (:constructor make-md5-state ()))
-  (a +md5-magic-a+ :type (unsigned-byte 32))
-  (b +md5-magic-b+ :type (unsigned-byte 32))
-  (c +md5-magic-c+ :type (unsigned-byte 32))
-  (d +md5-magic-d+ :type (unsigned-byte 32))
+  (regs (initial-md5-regs) :type md5-regs :read-only t)
   (amount 0 :type (unsigned-byte 29))
   (block (make-array 16 :element-type '(unsigned-byte 32)) :read-only t
 	 :type (simple-array (unsigned-byte 32) (16)))
@@ -298,7 +265,7 @@
 (declaim (inline copy-to-buffer))
 (defun copy-to-buffer (from from-offset count buffer buffer-offset)
   (declare (optimize (speed 3) (safety 0) (space 0) (debug 0))
-	   (type fixnum from-offset)
+	   (type (unsigned-byte 29) from-offset)
 	   (type (integer 0 63) count buffer-offset)
 	   (type (simple-array * (*)) from)
 	   (type (simple-array (unsigned-byte 8) (64)) buffer))
@@ -309,31 +276,32 @@
 	     (* buffer-offset vm:byte-bits))
    (* count vm:byte-bits))
   #-(and cmu x86)
-  (if (typep from 'simple-string)
-      (loop for buffer-index of-type (integer 0 64) from buffer-offset
-	    for from-index of-type fixnum from from-offset
-	    below (+ from-offset count)
-	    do
-	    (setf (aref buffer buffer-index)
-		  (char-code (schar from from-index))))
-      (loop for buffer-index of-type (integer 0 64) from buffer-offset
-	    for from-index of-type fixnum from from-offset
-	    below (+ from-offset count)
-	    do
-	    (setf (aref buffer buffer-index) (aref from from-index)))))
+  (etypecase from
+    (simple-string
+     (loop for buffer-index of-type (integer 0 64) from buffer-offset
+	   for from-index of-type fixnum from from-offset
+	   below (+ from-offset count)
+	   do
+	   (setf (aref buffer buffer-index)
+		 (char-code (schar from from-index)))))
+    ((simple-array (unsigned-byte 8) (*))
+     (loop for buffer-index of-type (integer 0 64) from buffer-offset
+	   for from-index of-type fixnum from from-offset
+	   below (+ from-offset count)
+	   do
+	   (setf (aref buffer buffer-index) (aref from from-index))))))
 
 (defun update-md5-state (state sequence &key (start 0) (end (length sequence)))
   (declare (type md5-state state)
 	   (type (simple-array * (*)) sequence)
 	   (type fixnum start end)
 	   (optimize (speed 3) (space 0) (debug 0)))
-  (let ((a (md5-state-a state)) (b (md5-state-b state))
-	(c (md5-state-c state)) (d (md5-state-d state))
+  (let ((regs (md5-state-regs state))
 	(block (md5-state-block state))
 	(buffer (md5-state-buffer state))
 	(buffer-index (md5-state-buffer-index state))
 	(length (- end start)))
-    (declare (type ub32 a b c d) (type fixnum length)
+    (declare (type md5-regs regs) (type fixnum length)
 	     (type (integer 0 63) buffer-index)
 	     (type (simple-array (unsigned-byte 32) (16)) block)
 	     (type (simple-array (unsigned-byte 8) (64)) buffer))
@@ -342,9 +310,12 @@
       (let ((amount (min (- 64 buffer-index) length)))
 	(declare (type (integer 0 63) amount))
 	(copy-to-buffer sequence start amount buffer buffer-index)
-	(setq start (the fixnum (+ start amount))))
-      (multiple-value-setq (a b c d)
-	(md5sum-update a b c d block buffer 0)))
+	(setq start (the fixnum (+ start amount)))
+	(when (>= start end)
+	  (setf (md5-state-buffer-index state) (+ buffer-index amount))
+	  (return-from update-md5-state state)))
+      (fill-block-ub8 block buffer 0)
+      (update-md5-block regs block))
     ;; Handle main-part and new-rest
     (etypecase sequence
       ((simple-array (unsigned-byte 8) (*))
@@ -352,8 +323,9 @@
 	   (declare (type (simple-array (unsigned-byte 8) (*)) sequence))
 	 (loop for offset of-type (unsigned-byte 29) from start below end by 64
 	       until (< (- end offset) 64)
-	       do (multiple-value-setq (a b c d)
-		    (md5sum-update a b c d block sequence offset))
+	       do
+	       (fill-block-ub8 block sequence offset)
+	       (update-md5-block regs block)
 	       finally
 	       (let ((amount (- end offset)))
 		 (unless (zerop amount)
@@ -364,37 +336,46 @@
 	   (declare (type simple-string sequence))
 	 (loop for offset of-type (unsigned-byte 29) from start below end by 64
 	       until (< (- end offset) 64)
-	       do (multiple-value-setq (a b c d)
-		    (md5sum-update-char a b c d block sequence offset))
+	       do
+	       (fill-block-char block sequence offset)
+	       (update-md5-block regs block)
 	       finally
 	       (let ((amount (- end offset)))
 		 (unless (zerop amount)
 		   (copy-to-buffer sequence offset amount buffer 0))
 		 (setf (md5-state-buffer-index state) amount))))))
-    (setf (md5-state-a state) a
-	  (md5-state-b state) b
-	  (md5-state-c state) c
-	  (md5-state-d state) d
-	  (md5-state-amount state) (+ (md5-state-amount state) length))
+    (setf (md5-state-amount state) (+ (md5-state-amount state) length))
     state))
 
 (defun finalize-md5-state (state)
   (declare (type md5-state state)
 	   (optimize (speed 3) (space 0) (debug 0)))
   (or (md5-state-finalized-p state)
-      (multiple-value-bind (a b c d)
-	  (md5sum-final (md5-state-a state) (md5-state-b state)
-			(md5-state-c state) (md5-state-d state)
-			(md5-state-block state)
-			(md5-state-buffer state)
-			0 (md5-state-buffer-index state)
-			(md5-state-amount state))
-	(setf (md5-state-a state) a
-	      (md5-state-b state) b
-	      (md5-state-c state) c
-	      (md5-state-d state) d
-	      (md5-state-finalized-p state)
-	      (md5sum-checksum a b c d)))))
+      (let ((regs (md5-state-regs state))
+	    (block (md5-state-block state))
+	    (buffer (md5-state-buffer state))
+	    (buffer-index (md5-state-buffer-index state))
+	    (total-length (md5-state-amount state)))
+	(declare (type md5-regs regs)
+		 (type (unsigned-byte 29) total-length)
+		 (type (integer 0 63) buffer-index)
+		 (type (simple-array ub32 (16)) block)
+		 (type (simple-array (unsigned-byte 8) (*)) buffer))
+	(setf (aref buffer buffer-index) #x80)
+	(loop for index of-type (integer 0 64)
+	      from (1+ buffer-index) below 64
+	      do (setf (aref buffer index) #x00))
+	(fill-block-ub8 block buffer 0)
+	(when (< buffer-index 56)
+	  (setf (aref block 14) (* total-length 8)))
+	(update-md5-block regs block)
+	(when (< 56 buffer-index 64)
+	  (loop for index of-type (integer 0 16) from 0 below 16
+		do (setf (aref block index) #x00000000))
+	  (setf (aref block 14) (* total-length 8))
+	  (update-md5-block regs block))
+	(setf (md5-state-finalized-p state)
+	      (md5regs-checksum regs)))))
 
 ;; High-Level Drivers
 
@@ -402,65 +383,36 @@
 
 (deftype buffer-index () `(integer 0 ,+buffer-size+))
 
-(defun md5sum-byte-stream (stream)
-  (declare (type stream)
-	   (optimize (speed 3) (space 0) (debug 0)))
-  (let ((block (make-array 16 :element-type 'ub32))
-	(buffer (make-array +buffer-size+ :element-type '(unsigned-byte 8)))
-	(length 0)
-	(a +md5-magic-a+) (b +md5-magic-b+)
-	(c +md5-magic-c+) (d +md5-magic-d+))
-    (declare (type ub32 a b c d length)
-	     (type (simple-array ub32 (16)) block)
-	     (type (simple-array (unsigned-byte 8) (*)) buffer))
-    (loop for bytes of-type buffer-index = (read-sequence buffer stream)
-	  do
-	  (incf length bytes)
-	  (loop for offset of-type buffer-index
-		from 0 below +buffer-size+ by 64
-		for rest-size of-type buffer-index = bytes
-		then (- rest-size block-size)
-		for block-size of-type (integer 0 64) = (min 64 rest-size)
-		do
-		(multiple-value-setq (a b c d)
-		  (if (< block-size 64)
-		      (md5sum-final a b c d block buffer offset
-				    block-size length)
-		      (md5sum-update a b c d block buffer offset)))
-		until (< block-size 64))
-	  until (< bytes +buffer-size+)
-	  finally (return (md5sum-checksum a b c d)))))
-
-(defun md5sum-char-stream (stream)
-  (declare (type stream)
-	   (optimize (speed 3) (space 0) (debug 0)))
-  (let ((block (make-array 16 :element-type 'ub32))
-	(buffer (make-string +buffer-size+))
-	(length 0)
-	(a +md5-magic-a+) (b +md5-magic-b+)
-	(c +md5-magic-c+) (d +md5-magic-d+))
-    (declare (type ub32 a b c d length)
-	     (type (simple-array ub32 (16)) block)
-	     (type simple-string buffer))
-    (loop for bytes of-type buffer-index = (read-sequence buffer stream)
-	  do
-	  (incf length bytes)
-	  (loop for offset of-type buffer-index
-		from 0 below +buffer-size+ by 64
-		for rest-size of-type buffer-index = bytes
-		then (- rest-size block-size)
-		for block-size of-type (integer 0 64) = (min 64 rest-size)
-		do
-		(multiple-value-setq (a b c d)
-		  (if (< block-size 64)
-		      (md5sum-final-char a b c d block buffer offset
-					 block-size length)
-		      (md5sum-update-char a b c d block buffer offset)))
-		until (< block-size 64))
-	  until (< bytes +buffer-size+)
-	  finally (return (md5sum-checksum a b c d)))))
+(defun md5sum-stream (stream)
+  (declare (optimize (speed 3) (space 0) (debug 0)))
+  (let ((state (make-md5-state)))
+    (declare (type md5-state state))
+    (cond
+      ((equal (stream-element-type stream) '(unsigned-byte 8))
+       (let ((buffer (make-array +buffer-size+ :element-type '(unsigned-byte 8))))
+	 (declare (type (simple-array (unsigned-byte 8) (#.md5::+buffer-size+))
+			buffer))
+	 (loop for bytes of-type buffer-index = (read-sequence buffer stream)
+	       do (update-md5-state state buffer :end bytes)
+	       until (< bytes +buffer-size+)
+	       finally
+	       (return (finalize-md5-state state)))))
+      ((equal (stream-element-type stream) 'character)
+       (let ((buffer (make-string +buffer-size+)))
+	 (declare (type (simple-string #.md5::+buffer-size+) buffer))
+	 (loop for bytes of-type buffer-index = (read-sequence buffer stream)
+	       do (update-md5-state state buffer :end bytes)
+	       until (< bytes +buffer-size+)
+	       finally
+	       (return (finalize-md5-state state)))))
+      (t
+       (error "Unsupported stream element-type ~S for stream ~S."
+	      (stream-element-type stream) stream)))))
 
 (defun md5sum-file (pathname)
   (declare (optimize (speed 3) (space 0) (debug 0)))
   (with-open-file (stream pathname :element-type '(unsigned-byte 8))
-    (md5sum-byte-stream stream)))
+    (md5sum-stream stream)))
+
+(eval-when (:compile-toplevel)
+  (setq ext:*inline-expansion-limit* *old-expansion-limit*))