Make sure we copy the syncMarker when reading it

Otherwise, the syncMarker will point to the reusable array that we use for
reading.

Author: colinmarc

sequencefile/header.go

@@ -97,7 +97,8 @@ func (r *Reader) ReadHeader() error {
 	}
 
 	r.Header.SyncMarker = string(marker)
-	r.syncMarkerBytes = marker
+	r.syncMarkerBytes = make([]byte, SyncSize)
+	copy(r.syncMarkerBytes, marker)
 
 	return nil
 }

sequencefile/reader.go

@@ -149,10 +149,11 @@ func (r *Reader) checkSyncAndScan(readValues bool) bool {
 
 	// If we never read the Header, infer the sync marker from the first time we
 	// see it.
-	if r.syncMarkerBytes == nil {
-		r.syncMarkerBytes = b
+	if r.syncMarkerBytes == []byte(nil) {
+		r.syncMarkerBytes = make([]byte, SyncSize)
+		copy(r.syncMarkerBytes, b)
 	} else if !bytes.Equal(b, r.syncMarkerBytes) {
-		r.close(fmt.Errorf("Invalid sync marker: %x", b))
+		r.close(fmt.Errorf("Invalid sync marker: %x vs %x", b, r.syncMarkerBytes))
 		return false
 	}