src/Pure/Thy/sessions.scala

           file.position(len - n)
 
           val buf = ByteBuffer.allocate(n)
           var i = 0
           var m = 0
-          var cont = true
-          while (cont) {
+          while ({
             m = file.read(buf)
             if (m != -1) i += m
-            cont = (m != -1 && n > i)
-          }
+            m != -1 && n > i
+          }) ()
 
           if (i == n) {
             val prefix = new String(buf.array(), 0, sha1_prefix.length, UTF8.charset)
             val s = new String(buf.array(), sha1_prefix.length, SHA1.digest_length, UTF8.charset)
             if (prefix == sha1_prefix) Some(s) else None