Read memory buffer via stream interface

Hi,

for example, i have

  unsigned char buff[ 100 ]

the buffer hold a sequences of raw bytes.  My question is, what is the
standard method of reading the `buff' via std::istream interface?

A relative question is: how to write to the `buff' via std::ostream
interface? I think this can be done by using std::stringstream, but i
am not sure of it.

Thanks.

-
woody