spreadsheet: add fast paths for appending rows/cells

spreadsheet/row.go

@@ -61,10 +61,22 @@ func (r Row) SetHidden(hidden bool) {
 
 // AddCell adds a cell to a spreadsheet.
 func (r Row) AddCell() Cell {
+	numCells := uint32(len(r.x.C))
+	var nextCellID *string
+	if numCells > 0 {
+		prevCellName := gooxml.Stringf("%s%d", IndexToColumn(numCells-1), r.RowNumber())
+		// previous cell has an expected name
+		if r.x.C[numCells-1].RAttr != nil && *r.x.C[numCells-1].RAttr == *prevCellName {
+			nextCellID = gooxml.Stringf("%s%d", IndexToColumn(numCells), r.RowNumber())
+		}
+	}
+
 	c := spreadsheetml.NewCT_Cell()
 	c.TAttr = spreadsheetml.ST_CellTypeN
-
 	r.x.C = append(r.x.C, c)
+
+	// fast path failed, so find the last cell and add another
+	if nextCellID == nil {
 		nextIdx := uint32(0)
 		for _, c := range r.x.C {
 			if c.RAttr != nil {
@@ -74,7 +86,9 @@ func (r Row) AddCell() Cell {
 				}
 			}
 		}
-	c.RAttr = gooxml.Stringf("%s%d", IndexToColumn(nextIdx), r.RowNumber())
+		nextCellID = gooxml.Stringf("%s%d", IndexToColumn(nextIdx), r.RowNumber())
+	}
+	c.RAttr = nextCellID
 	return Cell{r.w, r.s, r.x, c}
 }
 

spreadsheet/sheet.go

@@ -80,11 +80,27 @@ func (s Sheet) AddNumberedRow(rowNum uint32) Row {
 	return Row{s.w, s.x, r}
 }
 
+// addNumberedRowFast is a fast path that can be used when adding consecutive
+// rows and not skipping any.
+func (s Sheet) addNumberedRowFast(rowNum uint32) Row {
+	r := sml.NewCT_Row()
+	r.RAttr = gooxml.Uint32(rowNum)
+	s.x.SheetData.Row = append(s.x.SheetData.Row, r)
+	return Row{s.w, s.x, r}
+}
+
 // AddRow adds a new row to a sheet.  You can mix this with numbered rows,
 // however it will get confusing. You should prefer to use either automatically
 // numbered rows with AddRow or manually numbered rows with Row/AddNumberedRow
 func (s Sheet) AddRow() Row {
 	maxRowID := uint32(0)
+
+	numRows := uint32(len(s.x.SheetData.Row))
+	// fast path, adding consecutive rows
+	if numRows > 0 && s.x.SheetData.Row[numRows-1].RAttr != nil && *s.x.SheetData.Row[numRows-1].RAttr == numRows {
+		return s.addNumberedRowFast(numRows + 1)
+	}
+
 	// find the max row number
 	for _, r := range s.x.SheetData.Row {
 		if r.RAttr != nil && *r.RAttr > maxRowID {

spreadsheet/sheet_bench_test.go

@@ -0,0 +1,25 @@
+package spreadsheet_test
+
+import (
+	"testing"
+
+	"baliance.com/gooxml/spreadsheet"
+)
+
+func BenchmarkAddRow(b *testing.B) {
+	ss := spreadsheet.New()
+	sheet := ss.AddSheet()
+	for r := 0; r < b.N; r++ {
+		sheet.AddRow()
+	}
+}
+
+func BenchmarkAddCell(b *testing.B) {
+	ss := spreadsheet.New()
+	sheet := ss.AddSheet()
+	row := sheet.AddRow()
+
+	for c := 0; c < b.N; c++ {
+		row.AddCell()
+	}
+}