Gecko SDK for Delphi

I'm implementing nsIProtocolHandler in Delphi 7 with help of GeckoSDK, and
am missing the definition for nsISeekableStream,
based on
http://mxr.mozilla.org/firefox/source/xpcom/io/nsISeekableStream.idl
I tried below definition is it correct?
on the nsIInputStream instance I get over nsIUploadChannel, the seek method
throws 'not implemented' exceptions, is that correct or am I doing
something wrong?


const

NS_SEEK_SET = 0;
NS_SEEK_CUR = 1;
NS_SEEK_END = 2;

type

nsISeekableStream = interface(nsISupports)
['{8429d350-1040-4661-8b71-f2a6ba455980}']
//const NS_SEEK_* see above
procedure seek(whence:PRUint32;offset:PRUint64); safecall;
function tell:PRUint64; safecall;
procedure setEOF(); safecall;
end;