ByteStream class are an abstraction of the UNIX
file descriptors.
byte read;
int read;
EOF on end-of-file.
int
readRange (int, int) (start, num)
into MutableByteArray buffer;
buffer read at most num bytes from the receiving
ByteStream starting at start.
void write byte b;
int write byte b;
int
writeBytes int num
from pointer address;