diff --git a/scheme/ikarus.exceptions.ss b/scheme/ikarus.exceptions.ss
index 0e5fb74..35be597 100644
--- a/scheme/ikarus.exceptions.ss
+++ b/scheme/ikarus.exceptions.ss
@@ -25,7 +25,6 @@
       with-exception-handler raise raise-continuable 
       error assertion-violation))
 
-
   (define handlers
     (make-parameter
       (list 
diff --git a/scheme/ikarus.io.output-bytevectors.ss b/scheme/ikarus.io.output-bytevectors.ss
new file mode 100644
index 0000000..2183b77
--- /dev/null
+++ b/scheme/ikarus.io.output-bytevectors.ss
@@ -0,0 +1,173 @@
+;;; Ikarus Scheme -- A compiler for R6RS Scheme.
+;;; Copyright (C) 2006,2007  Abdulaziz Ghuloum
+;;; 
+;;; This program is free software: you can redistribute it and/or modify
+;;; it under the terms of the GNU General Public License version 3 as
+;;; published by the Free Software Foundation.
+;;; 
+;;; This program is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+;;; General Public License for more details.
+;;; 
+;;; You should have received a copy of the GNU General Public License
+;;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+
+(library (ikarus io output-bytevectors)
+  (export open-output-bytevector get-output-bytevector
+          with-output-to-bytevector open-bytevector-output-port)
+  (import 
+    (ikarus system $bytevectors)
+    (ikarus system $chars)
+    (ikarus system $fx)
+    (ikarus system $pairs)
+    (ikarus system $ports)
+    (ikarus system $io)
+    (except (ikarus) 
+      open-output-bytevector get-output-bytevector
+      with-output-to-bytevector open-bytevector-output-port))
+
+  (define-syntax message-case
+    (syntax-rules (else)
+      [(_ msg args 
+          [(msg-name msg-arg* ...) b b* ...] ... 
+          [else else1 else2 ...])
+       (let ([tmsg msg] [targs args])
+         (define-syntax match-and-bind
+           (syntax-rules ()
+             [(__ y () body)
+              (if (null? y) 
+                  body
+                  (error 'message-case "unmatched" (cons tmsg targs)))]
+             [(__ y (a a* (... ...)) body)
+              (if (pair? y)
+                  (let ([a (car y)] [d (cdr y)])
+                    (match-and-bind d (a* (... ...)) body))
+                  (error 'message-case "unmatched" (cons tmsg targs)))]))
+         (case tmsg
+           [(msg-name) 
+            (match-and-bind targs (msg-arg* ...) (begin b b* ...))] ...
+           [else else1 else2 ...]))]))
+  
+  (define concat 
+    (lambda (bv i ls)
+      (let ([n (sum i ls)])
+        (let ([outbv ($make-bytevector n)])
+          (let f ([n (copy outbv bv i n)] [ls ls])
+            (if (null? ls)
+                outbv
+                (let ([a ($car ls)])
+                  (f (copy outbv a ($bytevector-length a) n) ($cdr ls)))))))))
+  (define sum 
+    (lambda (ac ls)
+      (cond
+        [(null? ls) ac]
+        [else (sum ($fx+ ac ($bytevector-length ($car ls))) ($cdr ls))])))
+  
+
+  (define copy
+    (lambda (dst src n end)
+      (let f ([di end]
+              [si n])
+        (cond
+          [($fx= si 0) di]
+          [else
+           (let ([di ($fxsub1 di)] [si ($fxsub1 si)])
+             ($bytevector-set! dst di ($bytevector-u8-ref src si))
+             (f di si))]))))
+
+  (define bv-copy
+    (lambda (src)
+      (let ([n ($bytevector-length src)])
+        (let f ([src src] [dst ($make-bytevector n)] [i 0] [n n])
+          (cond
+            [($fx= i n) dst]
+            [else
+             ($bytevector-set! dst i ($bytevector-u8-ref src i))
+             (f src dst ($fxadd1 i) n)])))))
+
+
+
+  (define make-output-bytevector-handler
+    (lambda ()
+      (define buffer-list '())
+      (define open? #t)
+      (define output-handler
+        (lambda (msg . args)
+          (message-case msg args
+            [(write-byte b p)
+             (if (and (fixnum? b) ($fx<= 0 b) ($fx<= b 255))
+                 (if (output-port? p)
+                     (let ([idx ($port-index p)])
+                       (if ($fx< idx ($port-size p))
+                           (begin
+                             ($bytevector-set! ($port-buffer p) idx b)
+                             ($set-port-index! p ($fxadd1 idx)))
+                           (if open?
+                             (let ([buff ($port-buffer p)])
+                               (set! buffer-list (cons (bv-copy buff) buffer-list))
+                               ($bytevector-set! buff 0 b)
+                               ($set-port-index! p 1))
+                             (error 'write-byte "port is closed" p))))
+                     (error 'write-byte "not an output-port" p))
+                 (error 'write-byte "not a byte" b))]
+            [(write-char c p)
+             (if (char? c)
+                 (if (output-port? p)
+                     (let ([b ($char->fixnum c)])
+                       (if ($fx<= b 127)
+                           ($write-byte b p)
+                           (error 'write-char 
+                             "BUG: multibyte write of is not implemented" c)))
+                     (error 'write-char "not an output-port" p))
+                 (error 'write-char "not a character" c))]
+            [(flush-output-port p)
+             (void)]
+            [(close-port p)
+             (set! open? #f)]
+            [(port-name p) 'bytevector-port]
+            [(get-output-bytevector p) 
+             (concat 
+               ($port-buffer p) 
+               ($port-index p)
+               buffer-list)]
+            [(reset-port p)
+             ($set-port-index! p 0) 
+             (set! buffer-list '())]
+            [else 
+             (error 'bytevector-output-handler 
+                "unhandled message" (cons msg args))])))
+      output-handler))
+
+  (define open-output-bytevector 
+    (lambda ()
+      (make-output-port 
+        (make-output-bytevector-handler)
+        ($make-bytevector 59))))
+
+  (define get-output-bytevector
+    (lambda (p)
+      (if (output-port? p)
+          (($port-handler p) 'get-output-bytevector p)
+          (error 'get-output-bytevector "not an output port" p))))
+  
+  (define with-output-to-bytevector
+    (lambda (f)
+      (unless (procedure? f)
+        (error 'with-output-to-bytevector "not a procedure" f))
+      (let ([p (open-output-bytevector)])
+        (parameterize ([current-output-port p]) (f))
+        (get-output-bytevector p))))
+  
+  (define (open-bytevector-output-port)
+    (let ([p (open-output-bytevector)])
+      ;;; FIXME: should empty string
+      (values p 
+        (lambda ()
+          (let ([x (get-output-bytevector p)])
+            (($port-handler p) 'reset-port p)
+            x)))))
+
+
+)
diff --git a/scheme/last-revision b/scheme/last-revision
index 98a603e..75fccd6 100644
--- a/scheme/last-revision
+++ b/scheme/last-revision
@@ -1 +1 @@
-1170
+1171
diff --git a/scheme/makefile.ss b/scheme/makefile.ss
index b0305a4..ec8f212 100755
--- a/scheme/makefile.ss
+++ b/scheme/makefile.ss
@@ -72,6 +72,7 @@
     "ikarus.io.output-files.ss"
     "ikarus.io.input-strings.ss"
     "ikarus.io.output-strings.ss"
+    "ikarus.io.output-bytevectors.ss"
     "ikarus.hash-tables.ss"
     "ikarus.writer.ss"
     "ikarus.reader.ss"
@@ -338,9 +339,12 @@
     [set-port-mode!                              i]
     [with-input-from-string                      i]
     [open-output-string                          i]
+    [open-output-bytevector                      i]
     [open-input-string                           i]
     [get-output-string                           i]
+    [get-output-bytevector                       i]
     [with-output-to-string                       i]
+    [with-output-to-bytevector                   i]
     [console-input-port                          i]
     [console-output-port                         i]
     [reset-input-port!                           i]
@@ -1123,7 +1127,7 @@
     [native-eol-style                            i r ip]
     [native-transcoder                           i r ip]
     [open-bytevector-input-port                  r ip]
-    [open-bytevector-output-port                 r ip]
+    [open-bytevector-output-port                 i r ip]
     [open-file-input-port                        r ip]
     [open-file-input/output-port                 r ip]
     [open-file-output-port                       r ip]