does redo entry have data if not then wat happens on power failure

hi all
i have power failure of database and i had done some updates and commited and some uncommited data and redolog entries are made for it

then after that if there is power failure it will empty my database buffer cache and next time how will my database get the updated values
as they are already lost in my database buffer cache being empty now

so does it mean my redo entry has data in it???