http://blog.youkuaiyun.com/chencong112/article/details/7321096
http://wenku.baidu.com/link?url=mia6i-UxpWOTqqKklIzq92MhDRFyPaBwCDXRstgQf-SQKK3mW3xoHneYttKMHQ95HuPl1KGCq3WWuomF2upViBnR2J6ilua0yraj--VvKM_
http://blog.youkuaiyun.com/chencong112/article/details/7321096
http://wenku.baidu.com/link?url=mia6i-UxpWOTqqKklIzq92MhDRFyPaBwCDXRstgQf-SQKK3mW3xoHneYttKMHQ95HuPl1KGCq3WWuomF2upViBnR2J6ilua0yraj--VvKM_