in core/src/main/java/org/apache/shiro/session/mgt/SimpleSession.java [521:532]
private short getAlteredFieldsBitMask() {
int bitMask = 0;
bitMask = id != null ? bitMask | ID_BIT_MASK : bitMask;
bitMask = startTimestamp != null ? bitMask | START_TIMESTAMP_BIT_MASK : bitMask;
bitMask = stopTimestamp != null ? bitMask | STOP_TIMESTAMP_BIT_MASK : bitMask;
bitMask = lastAccessTime != null ? bitMask | LAST_ACCESS_TIME_BIT_MASK : bitMask;
bitMask = timeout != 0L ? bitMask | TIMEOUT_BIT_MASK : bitMask;
bitMask = expired ? bitMask | EXPIRED_BIT_MASK : bitMask;
bitMask = host != null ? bitMask | HOST_BIT_MASK : bitMask;
bitMask = !CollectionUtils.isEmpty(attributes) ? bitMask | ATTRIBUTES_BIT_MASK : bitMask;
return (short) bitMask;
}