Index: lucene/src/java/org/apache/lucene/util/CodecUtil.java
===================================================================
--- lucene/src/java/org/apache/lucene/util/CodecUtil.java	(revision 1086636)
+++ lucene/src/java/org/apache/lucene/util/CodecUtil.java	(working copy)
@@ -18,8 +18,8 @@
  */
 
 
-import org.apache.lucene.store.IndexOutput;
-import org.apache.lucene.store.IndexInput;
+import org.apache.lucene.store.DataInput;
+import org.apache.lucene.store.DataOutput;
 import org.apache.lucene.index.CorruptIndexException;
 import org.apache.lucene.index.IndexFormatTooNewException;
 import org.apache.lucene.index.IndexFormatTooOldException;
@@ -35,18 +35,16 @@
 
   private final static int CODEC_MAGIC = 0x3fd76c17;
 
-  public static IndexOutput writeHeader(IndexOutput out, String codec, int version)
+  public static DataOutput writeHeader(DataOutput out, String codec, int version)
     throws IOException {
-    final long start = out.getFilePointer();
+    BytesRef bytes = new BytesRef(codec);
+    if (bytes.length != codec.length() || bytes.length >= 128) {
+      throw new IllegalArgumentException("codec must be simple ASCII, less than 128 characters in length [got " + codec + "]");
+    }
     out.writeInt(CODEC_MAGIC);
     out.writeString(codec);
     out.writeInt(version);
 
-    // We require this so we can easily pre-compute header length
-    if (out.getFilePointer()-start != codec.length()+9) {
-      throw new IllegalArgumentException("codec must be simple ASCII, less than 128 characters in length [got " + codec + "]");
-    }
-
     return out;
   }
 
@@ -54,7 +52,7 @@
     return 9+codec.length();
   }
 
-  public static int checkHeader(IndexInput in, String codec, int minVersion, int maxVersion)
+  public static int checkHeader(DataInput in, String codec, int minVersion, int maxVersion)
     throws IOException {
 
     // Safety to guard against reading a bogus string:
Index: lucene/src/java/org/apache/lucene/util/automaton/fst/FST.java
===================================================================
--- lucene/src/java/org/apache/lucene/util/automaton/fst/FST.java	(revision 1086636)
+++ lucene/src/java/org/apache/lucene/util/automaton/fst/FST.java	(working copy)
@@ -21,8 +21,6 @@
 
 import org.apache.lucene.store.DataInput;
 import org.apache.lucene.store.DataOutput;
-import org.apache.lucene.store.IndexInput;
-import org.apache.lucene.store.IndexOutput;
 import org.apache.lucene.util.ArrayUtil;
 import org.apache.lucene.util.CodecUtil;
 import org.apache.lucene.util.automaton.fst.Builder.UnCompiledNode;
@@ -168,7 +166,7 @@
   }
 
   // create an existing FST
-  public FST(IndexInput in, Outputs<T> outputs) throws IOException {
+  public FST(DataInput in, Outputs<T> outputs) throws IOException {
     this.outputs = outputs;
     writer = null;
     CodecUtil.checkHeader(in, FILE_FORMAT_NAME, VERSION_START, VERSION_START);
@@ -250,7 +248,7 @@
     writer.posWrite = posSave;
   }
 
-  public void save(IndexOutput out) throws IOException {
+  public void save(DataOutput out) throws IOException {
     if (startNode == -1) {
       throw new IllegalStateException("call finish first");
     }