Tuesday, June 23, 2009

comparing with rsids

Now that the rsid is almost done (up to slight modifications and bugs fixing that will probably be necessary in the course of time) I turned to the document comparison itself.

The first more or less obvious use of the rsid is whenever two lines (text nodes) or two chars are compared. In addition to the condition that the two things being compared are the same I add the condition that their rsids are the same. This will ensure that the two things are not the same just by chance (which can easilly be the case when comparing chars or short and repetitive lines in the document) but because they were created in the same edit session.

Here is an example of how it goes in the CompareTxtNd function:

BOOL SwCompareLine::CompareTxtNd( const SwTxtNode& rDstNd,
const SwTxtNode& rSrcNd )

const SwDoc* pDestDoc = rDstNd.GetDoc();
const SwDoc* pSrcDoc = rSrcNd.GetDoc();

UINT32 nDstRsid = 0;
UINT32 nSrcRsid = 0;

// Only compare rsids if the rsidRoots are the same (docs have the same origin)
if ( pSrcDoc->getRsidRoot() == pDestDoc->getRsidRoot() )
nDstRsid = rDstNd.GetRsid( 0, rDstNd.Len() );
nSrcRsid = rSrcNd.GetRsid( 0, rSrcNd.Len() );

// erstmal ganz einfach!
if( rDstNd.GetTxt() == rSrcNd.GetTxt() && nDstRsid == nSrcRsid )
// der Text ist gleich, aber sind die "Sonderattribute" (0xFF) auch
// dieselben??
bRet = TRUE;
return bRet;

A few things to note:
The rsid check is applicable only if the two documents originate from the same document i.e. if their root rsids are the same, which is easily checked with the handy getRsidRoot() method;
If the root rsids are not the same or the documents don't have rsids, the two rsids will be 0;
To get the rsids I made a method of SwTxtNode, GetRsid(start,end);

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