func readN(rd *bufio.Reader, n int) ([]byte, error) {
b, err := rd.ReadN(n)
if err == bufio.ErrBufferFull {
tmp := make([]byte, n)
r := copy(tmp, b)
b = tmp
for {
nn, err := rd.Read(b[r:])
r += nn
if r >= n {
// Ignore error if we read enough.
break
}
if err != nil {
return nil, err
}
}
} else if err != nil {
return nil, err
}
return b, nil
}