anchor.diff:                              // then FLAG_ENDS_ON_BOUNDARY was set on the first
                               // overflow page in this block, since we can't set it
                               // here on this page, because this page has no header.
  -                            let sofarAfterBoundaryPage = buildOverflowBoundaryPage pb ba len sofarAfterRegularPages
  +                            let sofarAfterBoundaryPage = buildBoundaryPage sofarAfterRegularPages
                               let (nextPage,boundaryPage) = pageManager.GetRange(token)
                               pb.SetLastInt32(nextPage)
                               pb.Flush(fs)
  -                            utils.SeekPage(fs, pb.PageSize, nextPage)
  -                            fn sofarAfterBoundaryPage nextPage boundaryPage
  +                            utils.SeekPage(fs, pageSize, nextPage)
  +                            writeOneBlock sofarAfterBoundaryPage nextPage boundaryPage
                           else
                               (firstRegularPageNumber + numRegularPages, boundaryPageNumber)
   
  -        fn 0 startingNextPageNumber startingBoundaryPageNumber
  +        writeOneBlock 0 startingNextPageNumber startingBoundaryPageNumber
   
       let private buildParentPage (overflows:System.Collections.Generic.Dictionary<int,int32>) (pb:PageBuilder) (children:System.Collections.Generic.List<int32 * byte[]>) stop start =
           // assert stop > start
  
positive.code:                     let (nextPage,boundaryPage) = pageManager.GetRange(token)
                      pb.SetLastInt32(nextPage)
                      pb.Flush(fs)
                      utils.SeekPage(fs, pb.PageSize, nextPage)
                      fn sofarAfterFirstPage nextPage boundaryPage
                  else 
                      let firstRegularPageNumber = firstPageNumber + 1
                      // assert sofar <= len
  
negative.code:             if sofarBeforeFirstPage >= len then
                  (firstPageNumber, boundaryPageNumber)
              else
                  let sofarAfterFirstPage = buildFirstPage sofarBeforeFirstPage
                  // note that we haven't flushed this page yet.  we may have to fix
                  // a couple of things before it gets written out.
                  if firstPageNumber = boundaryPageNumber then
  