t>.
The <tt>zalloc</tt>, <tt>zfree</tt>, and <tt>opaque</tt> fields in the <tt>strm</tt>
structure must be initialized before calling <tt>deflateInit()</tt>.  Here they are
set to the <em>zlib</em> constant <tt>Z_NULL</tt> to request that <em>zlib</em> use
the default memory allocation routines.  An application may also choose to provide
custom memory allocation routines here.  <tt>deflateInit()</tt> will allocate on the
order of 256K bytes for the internal state.
(See <a href="zlib_tech.html"><em>zlib Tech