Don't write compound header to zero length files

Change-Id: Ie964ca8b870714d1c3e92469a771fab9a71f0633
Reviewed-on: https://gerrit.libreoffice.org/8220Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

sc/source/ui/unoobj/scdetect.cxx

@@ -510,57 +510,47 @@ OUString SAL_CALL ScFilterDetect::detect( uno::Sequence<beans::PropertyValue>& l
 
                 pFilter = NULL;
 
-                pStream->Seek( STREAM_SEEK_TO_END);
-                sal_Size nSize = pStream->Tell();
-                pStream->Seek( 0);
-                // Do not attempt to create an SotStorage on a
-                // 0-length stream as that would create the compound
-                // document header on the stream and effectively write to
-                // disk!
-                if (nSize > 0)
+                const char* pSearchFilterName = NULL;
+                if (aTypeName == "calc_Lotus")
                 {
-                    const char* pSearchFilterName = NULL;
-                    if (aTypeName == "calc_Lotus")
-                    {
-                        if (!detectThisFormat(*pStream, pLotus) && !detectThisFormat(*pStream, pLotusNew) && !detectThisFormat(*pStream, pLotus2))
-                            return OUString();
-
-                        pSearchFilterName = pFilterLotus;
-                    }
-                    else if (aTypeName == "calc_QPro")
-                    {
-                        if (!detectThisFormat(*pStream, pQPro))
-                            return OUString();
-
-                        pSearchFilterName = pFilterQPro6;
-                    }
-                    else if (aTypeName == "calc_SYLK")
-                    {
-                        if (!detectThisFormat(*pStream, pSylk))
-                            return OUString();
+                    if (!detectThisFormat(*pStream, pLotus) && !detectThisFormat(*pStream, pLotusNew) && !detectThisFormat(*pStream, pLotus2))
+                        return OUString();
 
-                        pSearchFilterName = pFilterSylk;
-                    }
-                    else if (aTypeName == "calc_DIF")
-                    {
-                        if (!detectThisFormat(*pStream, pDIF1) && !detectThisFormat(*pStream, pDIF2))
-                            return OUString();
+                    pSearchFilterName = pFilterLotus;
+                }
+                else if (aTypeName == "calc_QPro")
+                {
+                    if (!detectThisFormat(*pStream, pQPro))
+                        return OUString();
 
-                        pSearchFilterName = pFilterDif;
-                    }
-                    else if (aTypeName == "calc_dBase")
-                    {
-                        if (!lcl_MayBeDBase(*pStream))
-                            return OUString();
+                    pSearchFilterName = pFilterQPro6;
+                }
+                else if (aTypeName == "calc_SYLK")
+                {
+                    if (!detectThisFormat(*pStream, pSylk))
+                        return OUString();
 
-                        pSearchFilterName = pFilterDBase;
-                    }
+                    pSearchFilterName = pFilterSylk;
+                }
+                else if (aTypeName == "calc_DIF")
+                {
+                    if (!detectThisFormat(*pStream, pDIF1) && !detectThisFormat(*pStream, pDIF2))
+                        return OUString();
 
-                    if (!pSearchFilterName)
+                    pSearchFilterName = pFilterDif;
+                }
+                else if (aTypeName == "calc_dBase")
+                {
+                    if (!lcl_MayBeDBase(*pStream))
                         return OUString();
 
-                    pFilter = aMatcher.GetFilter4FilterName(OUString::createFromAscii(pSearchFilterName));
+                    pSearchFilterName = pFilterDBase;
                 }
+
+                if (!pSearchFilterName)
+                    return OUString();
+
+                pFilter = aMatcher.GetFilter4FilterName(OUString::createFromAscii(pSearchFilterName));
             }
         }
     }

sd/source/ui/unoidl/sddetect.cxx

@@ -352,6 +352,17 @@ OUString SAL_CALL SdFilterDetect::detect( Sequence< beans::PropertyValue >& lDes
                         pStm = aMedium.GetInStream();
                         if (!pStm)
                             pFilter = NULL;
+
+                        pStm->Seek(STREAM_SEEK_TO_END);
+                        const sal_Size nSize = pStm->Tell();
+                        pStm->Seek(STREAM_SEEK_TO_BEGIN);
+
+                        // Do not attempt to create an SotStorage on a
+                        // 0-length stream as that would create the compound
+                        // document header on the stream and effectively write to
+                        // disk!
+                        if (!nSize)
+                            pFilter = NULL;
                     }
 
                     if (pFilter && pStm)

starmath/source/smdetect.cxx

@@ -296,7 +296,20 @@ OUString SAL_CALL SmFilterDetect::detect( Sequence< PropertyValue >& lDescriptor
                 //this approach, to be fixed at a better level than here
                 SvStream *pStrm = aMedium.GetInStream();
                 aTypeName = OUString();
-                if (pStrm && !pStrm->GetError())
+
+                sal_Size nSize = 0;
+                if ( pStrm && !pStrm->GetError() )
+                {
+                    pStrm->Seek( STREAM_SEEK_TO_END );
+                    nSize = pStrm->Tell();
+                    pStrm->Seek( STREAM_SEEK_TO_BEGIN );
+                }
+
+                // Do not attempt to create an SotStorage on a
+                // 0-length stream as that would create the compound
+                // document header on the stream and effectively write to
+                // disk!
+                if ( nSize > 0 )
                 {
                     SotStorageRef aStorage = new SotStorage ( pStrm, false );
                     if ( !aStorage->GetError() )