BUF_LEN
avail = BUF_LEN - buf->used;
if (end >= BUF_LEN)
end -= BUF_LEN;
count = BUF_LEN - end;
count = BUF_LEN - buf->start;
unsigned char data[BUF_LEN];
if (buf->start >= BUF_LEN)
buf->start -= BUF_LEN;
avail = BUF_LEN - buf->used;
if (end >= BUF_LEN)
end -= BUF_LEN;
count = BUF_LEN - end;
count = BUF_LEN - buf->start;
if (buf->start >= BUF_LEN)
buf->start -= BUF_LEN;