diff --git a/scheme/ikarus.io.ss b/scheme/ikarus.io.ss
index de42964..378a9e2 100644
--- a/scheme/ikarus.io.ss
+++ b/scheme/ikarus.io.ss
@@ -206,6 +206,8 @@
   (define fast-char-text-tag       #b00000000010000)
   (define fast-u7-text-tag         #b00000000100000)
   (define fast-u8-text-tag         #b00000001100000)
+  (define fast-u16be-text-tag      #b00000010000000)
+  (define fast-u16le-text-tag      #b00000100000000)
   (define r6rs-mode-tag            #b01000000000000)
   (define closed-port-tag          #b10000000000000)
 
@@ -219,13 +221,15 @@
   (define fast-get-char-tag        #b00000000010101)
   (define fast-get-utf8-tag        #b00000000100101)
   (define fast-get-latin-tag       #b00000001100101)
+  (define fast-get-utf16be-tag     #b00000010000101)
+  (define fast-get-utf16le-tag     #b00000100000101)
 
   (define fast-put-byte-tag        #b00000000001010)
   (define fast-put-char-tag        #b00000000010110)
   (define fast-put-utf8-tag        #b00000000100110)
   (define fast-put-latin-tag       #b00000001100110)
 
-  (define fast-attrs-mask          #xFFF)
+  (define fast-attrs-mask          #b111111111111)
   (define-syntax $port-fast-attrs
     (identifier-syntax
       (lambda (x) 
@@ -750,11 +754,6 @@
        (die 'close-output-port "not an output port" p))
     ($close-port p))
 
-  ;(define-rrr port-has-port-position?)
-  ;(define-rrr port-position)
-  ;(define-rrr port-has-set-port-position!?)
-  ;(define-rrr set-port-position!)
-
   (define (refill-bv-buffer p who)
     (when ($port-closed? p) (die who "port is closed" p))
     (let ([bv ($port-buffer p)] [i ($port-index p)] [j ($port-size p)])
@@ -1019,14 +1018,27 @@
           (die who "not a textual port" p))
         (case (transcoder-codec tr)
           [(utf-8-codec)
-           ;;;
            ($set-port-attrs! p 
              (fxior textual-input-port-bits fast-u7-text-tag))
            (eof-object? (advance-bom p who '(#xEF #xBB #xBF)))]
+          [(utf-16-codec)
+           (let ([be? (advance-bom p who '(#xFE #xFF))])
+             (case be?
+               [(#t) 
+                ($set-port-attrs! p 
+                  (fxior textual-input-port-bits fast-u16be-text-tag))
+                #f]
+               [(#f)
+                (let ([le? (advance-bom p who '(#xFF #xFE))])
+                  (case le?
+                    [(#t #f) ;;; little by default
+                     ($set-port-attrs! p 
+                       (fxior textual-input-port-bits fast-u16le-text-tag))
+                     #f]
+                    [else #t]))]
+               [else #t]))]
           [else 
-           (die 'slow-get-char
-              "BUG: codec not handled"
-              (transcoder-codec tr))])))
+           (die who "BUG: codec not handled" (transcoder-codec tr))])))
     ;;;
     (define (lookahead-char-char-mode p who)
       (let ([str ($port-buffer p)]
@@ -1073,6 +1085,8 @@
                   (bytevector-u8-ref ($port-buffer p) i))]
                [else
                 (get-char-latin-mode p who 0)]))]
+          [(eq? m fast-get-utf16le-tag) (peek-utf16 p who 'little)]
+          [(eq? m fast-get-utf16be-tag) (peek-utf16 p who 'big)]
           [else 
            (if (speedup-input-port p who)
                (eof-object)
@@ -1094,47 +1108,120 @@
             [else
              ($set-port-index! p 1) 
              (string-ref str 0)]))))
+    (define (peek-utf16 p who endianness)
+      (define integer->char/invalid
+        (lambda (n)
+          (cond
+            [(fx<= n #xD7FF)   (integer->char n)]
+            [(fx< n  #xE000)   #\xFFFD]
+            [(fx<= n #x10FFFF) (integer->char n)]
+            [else               #\xFFFD])))
+      (let ([i ($port-index p)])
+        (cond
+          [(fx<= (fx+ i 2) ($port-size p))
+           (let ([w1 (bytevector-u16-ref ($port-buffer p) i endianness)])
+             (cond
+               [(or (fx< w1 #xD800) (fx> w1 #xDFFF))
+                (integer->char/invalid w1)]
+               [(not (and (fx<= #xD800 w1) (fx<= w1 #xDBFF)))
+                #\xFFFD]
+               [(fx<= (+ i 4) ($port-size p))
+                (let ([w2 (bytevector-u16-ref 
+                            ($port-buffer p) (+ i 2) endianness)])
+                  (cond
+                    [(not (and (fx<= #xDC00 w2) (fx<= w2 #xDFFF)))
+                     #\xFFFD]
+                    [else 
+                     (integer->char/invalid
+                       (fx+ #x10000
+                         (fxlogor
+                           (fxsll (fxand w1 #x3FF) 10)
+                           (fxand w2 #x3FF))))]))]
+               [else 
+                (let ([bytes (refill-bv-buffer p who)])
+                  (cond
+                    [(fx= bytes 0)
+                      #\xFFFD]
+                    [else
+                     (peek-utf16 p who endianness)]))]))]
+          [(fx< i ($port-size p))
+           (let ([bytes (refill-bv-buffer p who)])
+             (cond
+               [(fx= bytes 0)
+                #\xFFFD]
+               [else (peek-utf16 p who endianness)]))]
+          [else 
+           (let ([bytes (refill-bv-buffer p who)])
+             (if (fx= bytes 0)
+                 (eof-object)
+                 (peek-utf16 p who endianness)))])))
+    (define (get-utf16 p who endianness)
+      (define (invalid p who endianness n)
+        (case (transcoder-error-handling-mode (port-transcoder p))
+          [(ignore) (do-get-char p who endianness)]
+          [(replace) #\xFFFD]
+          [(raise)
+           (raise (make-i/o-decoding-error p n))]
+          [else (die who "BUG: invalid error handling mode" p)]))
+      (define (integer->char/invalid p who endianness n)
+        (cond
+          [(fx<= n #xD7FF)   (integer->char n)]
+          [(fx< n  #xE000)   (invalid p who endianness n)]
+          [(fx<= n #x10FFFF) (integer->char n)]
+          [else              (invalid p who endianness n)]))
+      (let ([i ($port-index p)])
+        (cond
+          [(fx<= (fx+ i 2) ($port-size p))
+           (let ([w1 (bytevector-u16-ref ($port-buffer p) i endianness)])
+             (cond
+               [(or (fx< w1 #xD800) (fx> w1 #xDFFF))
+                ($set-port-index! p (fx+ i 2))
+                (integer->char/invalid p who endianness w1)]
+               [(not (and (fx<= #xD800 w1) (fx<= w1 #xDBFF)))
+                ($set-port-index! p (fx+ i 2))
+                (invalid p who endianness w1)]
+               [(fx<= (+ i 4) ($port-size p))
+                (let ([w2 (bytevector-u16-ref 
+                            ($port-buffer p) (+ i 2) endianness)])
+                  (cond
+                    [(not (and (fx<= #xDC00 w2) (fx<= w2 #xDFFF)))
+                     ($set-port-index! p (fx+ i 2))
+                     (invalid p who endianness w1)]
+                    [else 
+                     ($set-port-index! p (fx+ i 4))
+                     (integer->char/invalid p who endianness
+                       (fx+ #x10000
+                         (fxlogor
+                           (fxsll (fxand w1 #x3FF) 10)
+                           (fxand w2 #x3FF))))]))]
+               [else 
+                (let ([bytes (refill-bv-buffer p who)])
+                  (cond
+                    [(fx= bytes 0)
+                     ($set-port-index! p ($port-size p))
+                     (invalid p who endianness w1)]
+                    [else
+                     (get-utf16 p who endianness)]))]))]
+          [(fx< i ($port-size p))
+           (let ([bytes (refill-bv-buffer p who)])
+             (cond
+               [(fx= bytes 0)
+                ($set-port-index! p ($port-size p))
+                (invalid p who endianness 
+                  (bytevector-u8-ref ($port-buffer p) ($port-index p)))]
+               [else (get-utf16 p who endianness)]))]
+          [else 
+           (let ([bytes (refill-bv-buffer p who)])
+             (if (fx= bytes 0)
+                 (eof-object)
+                 (get-utf16 p who endianness)))])))
+    (define (get-char p) 
+      (do-get-char p 'get-char))
     (define read-char
       (case-lambda
-        [(p) 
-         (define who 'read-char)
-         (let ([m ($port-fast-attrs p)])
-           (cond
-             [(eq? m fast-get-utf8-tag)
-              (let ([i ($port-index p)])
-                (cond
-                  [(fx< i ($port-size p))
-                   (let ([b (bytevector-u8-ref ($port-buffer p) i)])
-                     (cond
-                       [(fx< b 128) 
-                        ($set-port-index! p (fx+ i 1))
-                        (integer->char b)]
-                       [else (get-char-utf8-mode p who)]))]
-                  [else
-                   (get-char-utf8-mode p who)]))]
-             [(eq? m fast-get-char-tag)
-              (let ([i ($port-index p)])
-                (cond
-                  [(fx< i ($port-size p))
-                   ($set-port-index! p (fx+ i 1))
-                   (string-ref ($port-buffer p) i)]
-                  [else (get-char-char-mode p who)]))]
-             [(eq? m fast-get-latin-tag)
-              (let ([i ($port-index p)])
-                (cond
-                  [(fx< i ($port-size p))
-                   ($set-port-index! p (fx+ i 1))
-                   (integer->char 
-                     (bytevector-u8-ref ($port-buffer p) i))]
-                  [else
-                   (get-char-latin-mode p who 1)]))]
-             [else 
-              (if (speedup-input-port p who)
-                  (eof-object)
-                  (get-char p))]))]
-        [() (read-char (current-input-port))]))
-    (define (get-char p)
-      (define who 'get-char)
+        [(p) (do-get-char p 'read-char)]
+        [() (do-get-char (current-input-port) 'read-char)]))
+    (define (do-get-char p who)
       (let ([m ($port-fast-attrs p)])
         (cond
           [(eq? m fast-get-utf8-tag)
@@ -1165,10 +1252,12 @@
                   (bytevector-u8-ref ($port-buffer p) i))]
                [else
                 (get-char-latin-mode p who 1)]))]
+         [(eq? m fast-get-utf16le-tag) (get-utf16 p who 'little)]
+         [(eq? m fast-get-utf16be-tag) (get-utf16 p who 'big)]
           [else 
            (if (speedup-input-port p who)
                (eof-object)
-               (get-char p))]))))
+               (do-get-char p who))]))))
 
   ;;; ----------------------------------------------------------
   (define (assert-binary-input-port p who)
diff --git a/scheme/ikarus.unicode-conversion.ss b/scheme/ikarus.unicode-conversion.ss
index 162481f..ec04674 100644
--- a/scheme/ikarus.unicode-conversion.ss
+++ b/scheme/ikarus.unicode-conversion.ss
@@ -355,7 +355,7 @@
 ;;;      of W1. Terminate.
 ;;;
 ;;;   2) Determine if W1 is between 0xD800 and 0xDBFF. If not, the sequence
-;;;      is in die and no valid character can be obtained using W1.
+;;;      is in error and no valid character can be obtained using W1.
 ;;;      Terminate.
 ;;;
 ;;;   3) If there is no W2 (that is, the sequence ends with W1), or if W2
@@ -410,7 +410,7 @@
         [(str) 
          (unless (string? str)
            (die 'string->utf16 "not a string" str))
-         ($string->utf16 str 'big)]
+         ($string->utf16 str (native-endianness))]
         [(str endianness)
          (unless (string? str)
            (die 'string->utf16 "not a string" str))
@@ -458,7 +458,7 @@
              [(or (fx< w1 #xD800) (fx> w1 #xDFFF))
               (string-set! str n (integer->char/invalid w1))
               (fill bv endianness str (+ i 2) len (+ n 1))]
-             [(not (fx<= #xD800 w1 #xDBFF)) ;;; die sequence
+             [(not (fx<= #xD800 w1 #xDBFF)) ;;; error sequence
               (string-set! str n #\xFFFD)
               (fill bv endianness str (+ i 2) len (+ n 1))]
              [(<= (+ i 4) (bytevector-length bv))
@@ -466,7 +466,7 @@
                 (cond
                   [(not (<= #xDC00 w2 #xDFFF)) 
                    ;;; do we skip w2 also?
-                   ;;; I won't.  Just w1 is an die
+                   ;;; I won't.  Just w1 is an error
                    (string-set! str n #\xFFFD)
                    (fill bv endianness str (+ i 2) len (+ n 1))]
                   [else 
@@ -477,7 +477,7 @@
                                   (fxlogand w2 #x3FF)))))
                    (fill bv endianness str (+ i 4) len (+ n 1))]))]
              [else 
-              ;;; die again
+              ;;; error again
               (string-set! str n #\xFFFD)
               (fill bv endianness str (+ i 2) len (+ n 1))]))]))
     (define (decode bv endianness start)
@@ -531,7 +531,7 @@
         [(str) 
          (unless (string? str)
            (die who "not a string" str))
-         ($string->utf32 str 'big)]
+         ($string->utf32 str (native-endianness))]
         [(str endianness)
          (unless (string? str)
            (die who "not a string" str))
diff --git a/scheme/last-revision b/scheme/last-revision
index d0e5260..755d892 100644
--- a/scheme/last-revision
+++ b/scheme/last-revision
@@ -1 +1 @@
-1636
+1637
diff --git a/scheme/tests/io.ss b/scheme/tests/io.ss
index 129b374..3ac8ab0 100755
--- a/scheme/tests/io.ss
+++ b/scheme/tests/io.ss
@@ -202,6 +202,16 @@
         (make-transcoder (utf-8-codec) 'none 'raise))
       128)))
 
+(define (make-utf8-bytevector-range1) 
+  (u8-list->bytevector
+    (let f ([i 0] [j #x7F])
+      (cond
+        [(> i j) '()]
+        [else 
+         (cons* i (f (+ i 1) j))]))))
+
+
+
 (define (make-utf8-bytevector-range2) 
   (u8-list->bytevector
     (let f ([i #x80] [j #x7FF])
@@ -236,6 +246,15 @@
                 (fxior #b10000000 (fxand i #b111111))
                 (f (+ i 1) j))]))))
 
+(define (make-utf8-string-range1)
+  (list->string
+    (let f ([i 0] [j #x7F])
+      (cond
+        [(> i j) '()]
+        [else 
+         (cons (integer->char i)
+               (f (+ i 1) j))]))))
+
 (define (make-utf8-string-range2)
   (list->string
     (let f ([i #x80] [j #x7FF])
@@ -276,7 +295,16 @@
         [(char=? x (string-ref str i))
          (f (+ i 1))]
         [else 
-         (error #f "mismatch" x (string-ref str i) i)]))))
+         (error #f 
+           (format 
+             "mismatch at index ~a, got char ~a (code #x~x), \
+              expected char ~a (code #x~x)"
+               i
+               x
+               (char->integer x) 
+               (string-ref str i)
+               (char->integer (string-ref str i))))]))))
+
 
 (define (test-port-string-peeking-output p str) 
   (let f ([i 0])
@@ -294,7 +322,66 @@
         [else 
          (error #f "mismatch" x (string-ref str i) i)]))))
 
+
+(define (invalid-code? n) (not (valid-code? n)))
+(define (valid-code? n)
+  (cond
+    [(< n 0)       #f]
+    [(<= n #xD7FF) #t]
+    [(<  n #xE000) #f]
+    [(<= n #x10FFFF) #t]
+    [else (error 'valid-code? "out of range" n)]))
+
+
+
+(define (make-u16le-bv min max)
+  (u8-list->bytevector
+    (let f ([i min])
+      (cond
+        [(> i max) '()]
+        [(invalid-code? i) (f (+ i 1))]
+        [(< i #x10000)
+         (cons* 
+           (fxand i #xFF)
+           (fxsra i 8)
+           (f (+ i 1)))]
+        [else
+         (let ([ii (fx- i #x10000)])
+           (let ([w1 (fxior #xD800 (fxand #x3FF (fxsra ii 10)))]
+                 [w2 (fxior #xDC00 (fxand #x3FF ii))])
+             (cons* 
+               (fxand w1 #xFF)
+               (fxsra w1 8)
+               (fxand w2 #xFF)
+               (fxsra w2 8)
+               (f (+ i 1)))))]))))
+
+(define (make-string-slice min max)
+  (list->string
+    (let f ([i min])
+      (cond
+        [(> i max) '()]
+        [(invalid-code? i) (f (+ i 1))]
+        [else (cons (integer->char i) (f (+ i 1)))]))))
+
+
+(define (make-u16le-range1)
+  (make-u16le-bv 0 #x7FFF))
+(define (make-u16le-range2)
+  (make-u16le-bv #x8000 #x10FFFF))
+(define (make-utf16-string-range1)
+  (make-string-slice 0 #x7FFF))
+(define (make-utf16-string-range2)
+  (make-string-slice #x8000 #x10FFFF))
+
 (define (run-exhaustive-tests)
+  
+  (test "utf8 range 1"
+    (test-port-string-output
+      (open-bytevector-input-port (make-utf8-bytevector-range1)
+        (make-transcoder (utf-8-codec) 'none 'raise))
+      (make-utf8-string-range1)))
+
   (test "utf8 range 2"
     (test-port-string-output
       (open-bytevector-input-port (make-utf8-bytevector-range2)
@@ -312,7 +399,28 @@
       (open-bytevector-input-port (make-utf8-bytevector-range4)
         (make-transcoder (utf-8-codec) 'none 'raise))
       (make-utf8-string-range4)))
-  
+
+
+  (test "utf16 range 1"
+    (test-port-string-output
+      (open-bytevector-input-port (make-u16le-range1)
+        (make-transcoder (utf-16-codec) 'none 'raise))
+      (make-utf16-string-range1)))
+
+
+  (test "utf16 range 2"
+    (test-port-string-output
+      (open-bytevector-input-port (make-u16le-range2)
+        (make-transcoder (utf-16-codec) 'none 'raise))
+      (make-utf16-string-range2)))
+
+
+  (test "utf8 peek range 1"
+    (test-port-string-peeking-output
+      (open-bytevector-input-port (make-utf8-bytevector-range1)
+        (make-transcoder (utf-8-codec) 'none 'raise))
+      (make-utf8-string-range1)))
+
   (test "utf8 peek range 2"
     (test-port-string-peeking-output
       (open-bytevector-input-port (make-utf8-bytevector-range2)
@@ -330,7 +438,24 @@
       (open-bytevector-input-port (make-utf8-bytevector-range4)
         (make-transcoder (utf-8-codec) 'none 'raise))
       (make-utf8-string-range4)))
+
+  (test "utf16 peek range 1"
+    (test-port-string-peeking-output
+      (open-bytevector-input-port (make-u16le-range1)
+        (make-transcoder (utf-16-codec) 'none 'raise))
+      (make-utf16-string-range1)))
+
+  (test "utf16 peek range 2"
+    (test-port-string-peeking-output
+      (open-bytevector-input-port (make-u16le-range2)
+        (make-transcoder (utf-16-codec) 'none 'raise))
+      (make-utf16-string-range2)))
   
+  (test "utf8 range 1 string"
+    (test-port-string-output
+      (open-string-input-port (make-utf8-string-range1))
+      (make-utf8-string-range1)))
+
   (test "utf8 range 2 string"
     (test-port-string-output
       (open-string-input-port (make-utf8-string-range2))
@@ -509,18 +634,27 @@
                1]))
           #f #f #f)
         transcoder)))
-  (define (test name codec conv)
+  (define (test name codec s->bv bv->s)
     (printf "testing partial reads for ~s codec ... " name)
     (let ([s (make-test-string)])
+      (assert (string=? s (bv->s (s->bv s))))
       (let ([r (call-with-port 
-                 (make-slow-input-port (conv s) 
+                 (make-slow-input-port (s->bv s)
                    (make-transcoder codec 
                      (eol-style none) (error-handling-mode raise)))
                  get-string-all)])
-        (assert (string=? r s))))
+        (unless (string=? r s)
+          (if (= (string-length r) (string-length s))
+              (error #f "test failed")
+              (error #f "length mismatch" 
+                     (string-length s) (string-length r))))))
     (printf "ok\n"))
-  ;(test 'utf16 (utf-16-codec) string->utf16)
-  (test 'utf8 (utf-8-codec) string->utf8))
+  (test 'utf8 (utf-8-codec) 
+        string->utf8 
+        utf8->string)
+  (test 'utf16 (utf-16-codec) 
+        (lambda (x) (string->utf16 x 'little))
+        (lambda (x) (utf16->string x 'little))))
 
   (define-tests test-input-ports
     [eof-object?