http://wenku.baidu.com/link?url=-qLKtdiRHn_UFDU9nwCU_fuNvK0cKZlPA2UxaFmJ67MW23zzPFMG89L85IklodeZyWQOG6wO8MeX6AJ5yvC6YKVqtRIQ0GHjXyf5sy-fEf3
http://www.cnblogs.com/panjiwen/archive/2006/12/23/601421.html