Optimize ColumnNumberToName function performance, reduce about 50% memory usage and 50% time cost

lib.go

@@ -232,12 +232,18 @@ func ColumnNumberToName(num int) (string, error) {
 	if num < MinColumns || num > MaxColumns {
 		return "", ErrColumnNumber
 	}
-	var col string
+	estimatedLength := 0
+	for n := num; n > 0; n = (n - 1) / 26 {
+		estimatedLength++
+	}
+
+	result := make([]rune, estimatedLength)
 	for num > 0 {
-		col = string(rune((num-1)%26+65)) + col
+		estimatedLength--
+		result[estimatedLength] = rune((num-1)%26 + 'A')
 		num = (num - 1) / 26
 	}
-	return col, nil
+	return string(result), nil
 }
 
 // CellNameToCoordinates converts alphanumeric cell name to [X, Y] coordinates

sheet.go

@@ -30,11 +30,21 @@ import (
 	"github.com/mohae/deepcopy"
 )
 
+type Option func(ws *xlsxWorksheet)
+
+func WithMaxSheetRow(count int) Option {
+	return func(ws *xlsxWorksheet) {
+		if count > 0 {
+			ws.SheetData.Row = make([]xlsxRow, 0, count)
+		}
+	}
+}
+
 // NewSheet provides the function to create a new sheet by given a worksheet
 // name and returns the index of the sheets in the workbook after it appended.
 // Note that when creating a new workbook, the default worksheet named
 // `Sheet1` will be created.
-func (f *File) NewSheet(sheet string) (int, error) {
+func (f *File) NewSheet(sheet string, options ...Option) (int, error) {
 	var err error
 	if err = checkSheetName(sheet); err != nil {
 		return -1, err
@@ -57,7 +67,7 @@ func (f *File) NewSheet(sheet string) (int, error) {
 	// Update [Content_Types].xml
 	_ = f.setContentTypes("/xl/worksheets/sheet"+strconv.Itoa(sheetID)+".xml", ContentTypeSpreadSheetMLWorksheet)
 	// Create new sheet /xl/worksheets/sheet%d.xml
-	f.setSheet(sheetID, sheet)
+	f.setSheet(sheetID, sheet, options...)
 	// Update workbook.xml.rels
 	rID := f.addRels(f.getWorkbookRelsPath(), SourceRelationshipWorkSheet, fmt.Sprintf("/xl/worksheets/sheet%d.xml", sheetID), "")
 	// Update workbook.xml
@@ -230,13 +240,16 @@ func (f *File) setContentTypes(partName, contentType string) error {
 }
 
 // setSheet provides a function to update sheet property by given index.
-func (f *File) setSheet(index int, name string) {
+func (f *File) setSheet(index int, name string, options ...Option) {
 	ws := xlsxWorksheet{
 		Dimension: &xlsxDimension{Ref: "A1"},
 		SheetViews: &xlsxSheetViews{
 			SheetView: []xlsxSheetView{{WorkbookViewID: 0}},
 		},
 	}
+	for _, opt := range options {
+		opt(&ws)
+	}
 	sheetXMLPath := "xl/worksheets/sheet" + strconv.Itoa(index) + ".xml"
 	f.sheetMap[name] = sheetXMLPath
 	f.Sheet.Store(sheetXMLPath, &ws)

sheet_test.go

@@ -36,6 +36,9 @@ func TestNewSheet(t *testing.T) {
 	sheetID, err = f.NewSheet(":\\/?*[]")
 	assert.EqualError(t, err, ErrSheetNameInvalid.Error())
 	assert.Equal(t, -1, sheetID)
+	sheetID, err = f.NewSheet("Sheet3", WithMaxSheetRow(50))
+	assert.NoError(t, err)
+
 }
 
 func TestPanes(t *testing.T) {