try {
is = open(file);
FressianReader r = new FressianReader(is, FressianTraceFormat.READ_LOOKUP);
for (Object obj = r.readObject(); obj != null; obj = r.readObject()) {
if (obj instanceof Symbol) {
Symbol sym = (Symbol) obj;
symbols.put(sym.getId(), sym.getName());
} else if (obj instanceof ViewerTraceRecord) {
((ViewerTraceRecord) obj).fixup();
traceRecords.add((ViewerTraceRecord) obj);
} else {
System.err.println("Unknown object: " + obj);