def Run(self, args):
    """Reads a buffer on the client and sends it to the server."""
    # Make sure we limit the size of our output
    if args.length > constants.CLIENT_MAX_BUFFER_SIZE:
      raise RuntimeError("Can not read buffers this large.")

    data = vfs.ReadVFS(args.pathspec, args.offset, args.length)

    digest = hashlib.sha256(data).digest()

    # Now report the hash of this blob to our flow as well as the offset and
    # length.
    self.SendReply(
        rdf_client.BufferReference(
            offset=args.offset, length=len(data), data=digest))