code: public static Map<String, Integer> offsetMap(Schema sch) {
  		int pos = 0;
  		Map<String, Integer> offsetMap = new HashMap<String, Integer>();
  		for (String fldname : sch.fields()) {
  			offsetMap.put(fldname, pos);
  			pos += Page.maxSize(sch.type(fldname));
  		}
  		return offsetMap;
  	}
docs: Returns the map of field name to offset of a specified schema.
  
  @param sch
  the table's schema
  
  @return the offset map