diff --git a/src/ikarus.boot b/src/ikarus.boot
index 2d2bcc1..59ca01e 100644
Binary files a/src/ikarus.boot and b/src/ikarus.boot differ
diff --git a/src/ikarus.transcoders.ss b/src/ikarus.transcoders.ss
new file mode 100644
index 0000000..aca8ade
--- /dev/null
+++ b/src/ikarus.transcoders.ss
@@ -0,0 +1,94 @@
+
+(library (ikarus transcoders)
+  (export string->utf8-bytevector
+          #;utf8-bytevector->string)
+  (import (except (ikarus) string->utf8-bytevector)
+          (ikarus system $strings)
+          (ikarus system $bytevectors)
+          (ikarus system $fx)
+          (ikarus system $chars)
+          )
+
+  ;;; From http://en.wikipedia.org/wiki/UTF-8
+  ;;; hexadecimal      binary scalar value            UTF8
+  ;;; 000000-00007F    00000000_00000000_0zzzzzzz     0zzzzzzz
+  ;;; 000080-0007FF    00000000_00000yyy_yyzzzzzz     110yyyyy 10zzzzzz
+  ;;; 000800-00FFFF    00000000_xxxxyyyy_yyzzzzzz     1110xxxx 10yyyyyy 10zzzzzz
+  ;;; 010000-10FFFF    000wwwxx_xxxxyyyy_yyzzzzzz     11110www 10xxxxxx 10yyyyyy 10zzzzzz
+
+  ;;; valid ranges:  [000000 - 00D7FF] \union [00E000 - 10FFFF]
+  ;;; invalid hole:  [00D800 - 00DFFF]
+
+  ;;; handling-modes: ignore, replace, raise
+  ;;; ignore: skips over the offending bytes
+  ;;; replace: places a U+FFFD in place of the malformed bytes
+  ;;; raise: raises an error
+
+  (define (utf8-string-size str)
+    (let f ([str str] [i 0] [j ($string-length str)] [n 0])
+      (cond
+        [($fx= i j) n]
+        [else
+         (let ([c ($string-ref str i)])
+           (let ([b ($char->fixnum c)])
+             (f str ($fxadd1 i) j
+                ($fx+ n
+                  (cond
+                    [($fx<= b #x7F)    1]
+                    [($fx<= b #x7FF)   2]
+                    [($fx<= b #xFFFF)  3]
+                    [else              4])))))])))
+
+  (define (fill-utf8-bytevector bv str)
+    (let f ([bv bv] [str str] [i 0] [j 0] [n ($string-length str)])
+      (cond
+        [($fx= i n) bv]
+        [else
+         (let ([c ($string-ref str i)])
+           (let ([b ($char->fixnum c)])
+             (cond
+              [($fx<= b #x7F)
+               ($bytevector-set! bv j b)
+               (f bv str ($fxadd1 i) ($fxadd1 j) n)]
+              [($fx<= b #x7FF)  
+               ($bytevector-set! bv j
+                 ($fxlogor #b11000000 ($fxsra b 6)))
+               ($bytevector-set! bv ($fx+ j 1)
+                 ($fxlogor #b10000000 ($fxlogand b #b111111)))
+               (f bv str ($fxadd1 i) ($fx+ j 2) n)]
+              [($fx<= b #xFFFF) 
+               ($bytevector-set! bv j
+                 ($fxlogor #b11100000 ($fxsra b 12)))
+               ($bytevector-set! bv ($fx+ j 1)
+                 ($fxlogor #b10000000 ($fxlogand ($fxsra b 6) #b111111)))
+               ($bytevector-set! bv ($fx+ j 2)
+                 ($fxlogor #b10000000 ($fxlogand b #b111111)))
+               (f bv str ($fxadd1 i) ($fx+ j 3) n)]
+              [else
+               ($bytevector-set! bv j
+                 ($fxlogor #b11110000 ($fxsra b 18)))
+               ($bytevector-set! bv ($fx+ j 1)
+                 ($fxlogor #b10000000 ($fxlogand ($fxsra b 12) #b111111)))
+               ($bytevector-set! bv ($fx+ j 2)
+                 ($fxlogor #b10000000 ($fxlogand ($fxsra b 6) #b111111)))
+               ($bytevector-set! bv ($fx+ j 3)
+                 ($fxlogor #b10000000 ($fxlogand b #b111111)))
+               (f bv str ($fxadd1 i) ($fx+ j 4) n)])))])))
+
+
+  (define string->utf8-bytevector
+    (lambda (str)
+      (unless (string? str) 
+        (error 'string->utf8-bytevector "~s is not a string" str))
+      (fill-utf8-bytevector
+        ($make-bytevector (utf8-string-size str))
+        str)))
+
+
+  )
+
+
+#!eof
+       (unless (memq handling-mode '(ignore replace raise)) 
+         (error 'string->utf8-bytevector "~s is not a valid hanlding-mode, shound be one of ignore, replace, or raise" handling-mode))
+
diff --git a/src/makefile.ss b/src/makefile.ss
index e593a33..69e4e72 100755
--- a/src/makefile.ss
+++ b/src/makefile.ss
@@ -69,6 +69,7 @@
     "ikarus.posix.ss"
     "ikarus.timer.ss"
     "ikarus.bytevectors.ss"
+    "ikarus.transcoders.ss"
     "ikarus.main.ss"))
 
 (define ikarus-system-macros
@@ -291,6 +292,7 @@
     [bytevector->sint-list   i]
     [uint-list->bytevector   i]
     [sint-list->bytevector   i]
+    [string->utf8-bytevector i]
 
     [for-each                i r]
     [map                     i r]