diff -r dfcf667bbfed -r b6960fc09ef3 src/Pure/library.scala
--- a/src/Pure/library.scala	Sun Dec 27 22:36:47 2009 +0100
+++ b/src/Pure/library.scala	Sun Dec 27 23:09:16 2009 +0100
@@ -36,6 +36,52 @@
   }
 
 
+  /* permissive UTF-8 decoding */
+
+  // see also http://en.wikipedia.org/wiki/UTF-8#Description
+  def decode_permissive_utf8(text: CharSequence): String =
+  {
+    val buf = new java.lang.StringBuilder(text.length)
+    var code = -1
+    var rest = 0
+    def flush()
+    {
+      if (code != -1) {
+        if (rest == 0 && Character.isValidCodePoint(code))
+          buf.appendCodePoint(code)
+        else buf.append('\uFFFD')
+        code = -1
+        rest = 0
+      }
+    }
+    def init(x: Int, n: Int)
+    {
+      flush()
+      code = x
+      rest = n
+    }
+    def push(x: Int)
+    {
+      if (rest <= 0) init(x, -1)
+      else {
+        code <<= 6
+        code += x
+        rest -= 1
+      }
+    }
+    for (i <- 0 until text.length) {
+      val c = text.charAt(i)
+      if (c < 128) { flush(); buf.append(c) }
+      else if ((c & 0xC0) == 0x80) push(c & 0x3F)
+      else if ((c & 0xE0) == 0xC0) init(c & 0x1F, 1)
+      else if ((c & 0xF0) == 0xE0) init(c & 0x0F, 2)
+      else if ((c & 0xF8) == 0xF0) init(c & 0x07, 3)
+    }
+    flush()
+    buf.toString
+  }
+
+
   /* timing */
 
   def timeit[A](e: => A) =