tdf#89319 remove redundant file seekings in XLS export

Normally StartRecord() is called with closed records and with end position
of the stream set by EndRecord(), so the mrStrm.Seek( STREAM_SEEK_TO_END )
in the InitRecord() is a redundant call. The patch removes this call,
and sets it only for the non redundant cases: when there is an unclosed
record in StartRecord() or a continue record in StartContinue().

Change-Id: Iecbcaf01cbfe6094fa73d5ed41dba5f01417edb3

sc/source/filter/excel/xestream.cxx

@@ -109,6 +109,8 @@ void XclExpStream::StartRecord( sal_uInt16 nRecId, sal_Size nRecSize )
     DisableEncryption();
     mnMaxContSize = mnCurrMaxSize = mnMaxRecSize;
     mnPredictSize = nRecSize;
+    if ( mbInRec )
+        mrStrm.Seek( STREAM_SEEK_TO_END );
     mbInRec = true;
     InitRecord( nRecId );
     SetSliceSize( 0 );
@@ -380,7 +382,7 @@ sal_uInt64 XclExpStream::SetSvStreamPos(sal_uInt64 const nPos)
 
 void XclExpStream::InitRecord( sal_uInt16 nRecId )
 {
-    mrStrm.Seek( STREAM_SEEK_TO_END );
+    OSL_ENSURE( mrStrm.remainingSize() == 0, "XclExpStream::InitRecord - not in end position" );
     mrStrm.WriteUInt16( nRecId );
 
     mnLastSizePos = mrStrm.Tell();
@@ -417,6 +419,7 @@ void XclExpStream::StartContinue()
     UpdateRecSize();
     mnCurrMaxSize = mnMaxContSize;
     mnPredictSize -= mnCurrSize;
+    mrStrm.Seek( STREAM_SEEK_TO_END );
     InitRecord( EXC_ID_CONT );
 }