 structure. <b>comp_nid</b> is the compression algorithm to use or <b>NID_undef</b> to use the default algorithm (zlib compression). <b>in</b> is the content to be compressed. <b>flags</b> is an optional set of flags.</p>

<p>The only currently supported compression algorithm is zlib using the NID NID_zlib_compression.</p>

<p>If zlib support is not compiled into OpenSSL then CMS_compress() will return an error.</p>

<p>If the <b>CMS_TEXT</b> flag is set MIME headers for type <b>text/plain</b> are prepended