public override Long readBuf(Buf other, long n)
{
if (p.m_pos >= p.m_size) return null;
int len = Math.Min(p.m_size-p.m_pos, (int)n);
other.pipeFrom(p.m_buf, p.m_pos, len);
p.m_pos += len;
return Long.valueOf(len);
}