实现安全散列函数sha1，可对任意不超过2^64大小的文件进行操作，产生160bits的摘要，因本人较懒，注释较少，不过程序很好理解。是用c语言实现的。-Secure hash function sha1, can not exceed 2 ^ 64 any size file to operate, generate 160bits summary, because I am more lazy, notes less, but the program is well understood.