Improve security and simplify code

- Make variable name more semantic
- Reduce cyclomatic complexities for the formula calculate function
- Support specified unzip size limit on open file options, avoid zip bombs vulnerability attack
- Typo fix for documentation and error message

21 files changed, 165 insertions, 120 deletions

diff --git a/calc.go b/calc.go
index a03520b..eb6ff75 100644
--- a/calc.go
+++ b/calc.go
@@ -6026,6 +6026,39 @@ func (fn *formulaFuncs) DATE(argsList *list.List) formulaArg {
 	return newStringFormulaArg(timeFromExcelTime(daysBetween(excelMinTime1900.Unix(), d)+1, false).String())
 }
 
+// calcDateDif is an implementation of the formula function DATEDIF,
+// calculation difference between two dates.
+func calcDateDif(unit string, diff float64, seq []int, startArg, endArg formulaArg) float64 {
+	ey, sy, em, sm, ed, sd := seq[0], seq[1], seq[2], seq[3], seq[4], seq[5]
+	switch unit {
+	case "d":
+		diff = endArg.Number - startArg.Number
+	case "md":
+		smMD := em
+		if ed < sd {
+			smMD--
+		}
+		diff = endArg.Number - daysBetween(excelMinTime1900.Unix(), makeDate(ey, time.Month(smMD), sd)) - 1
+	case "ym":
+		diff = float64(em - sm)
+		if ed < sd {
+			diff--
+		}
+		if diff < 0 {
+			diff += 12
+		}
+	case "yd":
+		syYD := sy
+		if em < sm || (em == sm && ed < sd) {
+			syYD++
+		}
+		s := daysBetween(excelMinTime1900.Unix(), makeDate(syYD, time.Month(em), ed))
+		e := daysBetween(excelMinTime1900.Unix(), makeDate(sy, time.Month(sm), sd))
+		diff = s - e
+	}
+	return diff
+}
+
 // DATEDIF function calculates the number of days, months, or years between
 // two dates. The syntax of the function is:
 //
@@ -6051,8 +6084,6 @@ func (fn *formulaFuncs) DATEDIF(argsList *list.List) formulaArg {
 	ey, emm, ed := endDate.Date()
 	sm, em, diff := int(smm), int(emm), 0.0
 	switch unit {
-	case "d":
-		return newNumberFormulaArg(endArg.Number - startArg.Number)
 	case "y":
 		diff = float64(ey - sy)
 		if em < sm || (em == sm && ed < sd) {
@@ -6069,28 +6100,8 @@ func (fn *formulaFuncs) DATEDIF(argsList *list.List) formulaArg {
 			mdiff += 12
 		}
 		diff = float64(ydiff*12 + mdiff)
-	case "md":
-		smMD := em
-		if ed < sd {
-			smMD--
-		}
-		diff = endArg.Number - daysBetween(excelMinTime1900.Unix(), makeDate(ey, time.Month(smMD), sd)) - 1
-	case "ym":
-		diff = float64(em - sm)
-		if ed < sd {
-			diff--
-		}
-		if diff < 0 {
-			diff += 12
-		}
-	case "yd":
-		syYD := sy
-		if em < sm || (em == sm && ed < sd) {
-			syYD++
-		}
-		s := daysBetween(excelMinTime1900.Unix(), makeDate(syYD, time.Month(em), ed))
-		e := daysBetween(excelMinTime1900.Unix(), makeDate(sy, time.Month(sm), sd))
-		diff = s - e
+	case "d", "md", "ym", "yd":
+		diff = calcDateDif(unit, diff, []int{ey, sy, em, sm, ed, sd}, startArg, endArg)
 	default:
 		return newErrorFormulaArg(formulaErrorVALUE, "DATEDIF has invalid unit")
 	}
diff --git a/comment_test.go b/comment_test.go
index f1b60dc..fb36d29 100644
--- a/comment_test.go
+++ b/comment_test.go
@@ -3,9 +3,11 @@
 // the LICENSE file.
 //
 // Package excelize providing a set of functions that allow you to write to
-// and read from XLSX files. Support reads and writes XLSX file generated by
-// Microsoft Excel™ 2007 and later. Support save file without losing original
-// charts of XLSX. This library needs Go version 1.15 or later.
+// and read from XLSX / XLSM / XLTM files. Supports reading and writing
+// spreadsheet documents generated by Microsoft Excel™ 2007 and later. Supports
+// complex components by high compatibility, and provided streaming API for
+// generating or reading data from a worksheet with huge amounts of data. This
+// library needs Go version 1.15 or later.
 
 package excelize
 
diff --git a/crypt.go b/crypt.go
index a0096c9..24ac7ec 100644
--- a/crypt.go
+++ b/crypt.go
@@ -3,9 +3,11 @@
 // the LICENSE file.
 //
 // Package excelize providing a set of functions that allow you to write to
-// and read from XLSX files. Support reads and writes XLSX file generated by
-// Microsoft Excel™ 2007 and later. Support save file without losing original
-// charts of XLSX. This library needs Go version 1.15 or later.
+// and read from XLSX / XLSM / XLTM files. Supports reading and writing
+// spreadsheet documents generated by Microsoft Excel™ 2007 and later. Supports
+// complex components by high compatibility, and provided streaming API for
+// generating or reading data from a worksheet with huge amounts of data. This
+// library needs Go version 1.15 or later.
 
 package excelize
 
@@ -15,6 +17,7 @@ import (
 	"crypto/cipher"
 	"crypto/hmac"
 	"crypto/md5"
+	"crypto/rand"
 	"crypto/sha1"
 	"crypto/sha256"
 	"crypto/sha512"
@@ -22,7 +25,6 @@ import (
 	"encoding/binary"
 	"encoding/xml"
 	"hash"
-	"math/rand"
 	"reflect"
 	"strings"
 
diff --git a/crypt_test.go b/crypt_test.go
index 6a882e5..68ff5b8 100644
--- a/crypt_test.go
+++ b/crypt_test.go
@@ -3,9 +3,11 @@
 // the LICENSE file.
 //
 // Package excelize providing a set of functions that allow you to write to
-// and read from XLSX files. Support reads and writes XLSX file generated by
-// Microsoft Excel™ 2007 and later. Support save file without losing original
-// charts of XLSX. This library needs Go version 1.15 or later.
+// and read from XLSX / XLSM / XLTM files. Supports reading and writing
+// spreadsheet documents generated by Microsoft Excel™ 2007 and later. Supports
+// complex components by high compatibility, and provided streaming API for
+// generating or reading data from a worksheet with huge amounts of data. This
+// library needs Go version 1.15 or later.
 
 package excelize
 
diff --git a/datavalidation_test.go b/datavalidation_test.go
index f0afe5f..0cb5929 100644
--- a/datavalidation_test.go
+++ b/datavalidation_test.go
@@ -3,9 +3,11 @@
 // the LICENSE file.
 //
 // Package excelize providing a set of functions that allow you to write to
-// and read from XLSX files. Support reads and writes XLSX file generated by
-// Microsoft Excel™ 2007 and later. Support save file without losing original
-// charts of XLSX. This library needs Go version 1.15 or later.
+// and read from XLSX / XLSM / XLTM files. Supports reading and writing
+// spreadsheet documents generated by Microsoft Excel™ 2007 and later. Supports
+// complex components by high compatibility, and provided streaming API for
+// generating or reading data from a worksheet with huge amounts of data. This
+// library needs Go version 1.15 or later.
 
 package excelize
 
diff --git a/date_test.go b/date_test.go
index 38898b0..2addc4a 100644
--- a/date_test.go
+++ b/date_test.go
@@ -85,5 +85,5 @@ func TestExcelDateToTime(t *testing.T) {
 	}
 	// Check error case
 	_, err := ExcelDateToTime(-1, false)
-	assert.EqualError(t, err, "invalid date value -1.000000, negative values are not supported supported")
+	assert.EqualError(t, err, "invalid date value -1.000000, negative values are not supported")
 }
diff --git a/errors.go b/errors.go
index 0edb697..aee4420 100644
--- a/errors.go
+++ b/errors.go
@@ -16,26 +16,36 @@ import (
 	"fmt"
 )
 
+// newInvalidColumnNameError defined the error message on receiving the invalid column name.
 func newInvalidColumnNameError(col string) error {
 	return fmt.Errorf("invalid column name %q", col)
 }
 
+// newInvalidRowNumberError defined the error message on receiving the invalid row number.
 func newInvalidRowNumberError(row int) error {
 	return fmt.Errorf("invalid row number %d", row)
 }
 
+// newInvalidCellNameError defined the error message on receiving the invalid cell name.
 func newInvalidCellNameError(cell string) error {
 	return fmt.Errorf("invalid cell name %q", cell)
 }
 
+// newInvalidExcelDateError defined the error message on receiving the data with negative values.
 func newInvalidExcelDateError(dateValue float64) error {
-	return fmt.Errorf("invalid date value %f, negative values are not supported supported", dateValue)
+	return fmt.Errorf("invalid date value %f, negative values are not supported", dateValue)
 }
 
+// newUnsupportChartType defined the error message on receiving the chart type are unsupported.
 func newUnsupportChartType(chartType string) error {
 	return fmt.Errorf("unsupported chart type %s", chartType)
 }
 
+// newUnzipSizeLimitError defined the error message on unzip size exceeds the limit.
+func newUnzipSizeLimitError(unzipSizeLimit int64) error {
+	return fmt.Errorf("unzip size exceeds the %d bytes limit", unzipSizeLimit)
+}
+
 var (
 	// ErrStreamSetColWidth defined the error message on set column width in
 	// stream writing mode.
diff --git a/errors_test.go b/errors_test.go
index 207e80a..971802f 100644
--- a/errors_test.go
+++ b/errors_test.go
@@ -21,5 +21,5 @@ func TestNewInvalidCellNameError(t *testing.T) {
 }
 
 func TestNewInvalidExcelDateError(t *testing.T) {
-	assert.EqualError(t, newInvalidExcelDateError(-1), "invalid date value -1.000000, negative values are not supported supported")
+	assert.EqualError(t, newInvalidExcelDateError(-1), "invalid date value -1.000000, negative values are not supported")
 }
diff --git a/excelize.go b/excelize.go
index 0091c82..fafa57f 100644
--- a/excelize.go
+++ b/excelize.go
@@ -21,6 +21,7 @@ import (
 	"io/ioutil"
 	"os"
 	"path"
+	"path/filepath"
 	"strconv"
 	"strings"
 	"sync"
@@ -59,21 +60,27 @@ type charsetTranscoderFn func(charset string, input io.Reader) (rdr io.Reader, e
 
 // Options define the options for open spreadsheet.
 type Options struct {
-	Password string
+	Password       string
+	UnzipSizeLimit int64
 }
 
-// OpenFile take the name of an spreadsheet file and returns a populated spreadsheet file struct
-// for it. For example, open spreadsheet with password protection:
+// OpenFile take the name of an spreadsheet file and returns a populated
+// spreadsheet file struct for it. For example, open spreadsheet with
+// password protection:
 //
 //    f, err := excelize.OpenFile("Book1.xlsx", excelize.Options{Password: "password"})
 //    if err != nil {
 //        return
 //    }
 //
-// Note that the excelize just support decrypt and not support encrypt currently, the spreadsheet
-// saved by Save and SaveAs will be without password unprotected.
+// Note that the excelize just support decrypt and not support encrypt
+// currently, the spreadsheet saved by Save and SaveAs will be without
+// password unprotected.
+//
+// UnzipSizeLimit specified the unzip size limit in bytes on open the
+// spreadsheet, the default size limit is 16GB.
 func OpenFile(filename string, opt ...Options) (*File, error) {
-	file, err := os.Open(filename)
+	file, err := os.Open(filepath.Clean(filename))
 	if err != nil {
 		return nil, err
 	}
@@ -89,6 +96,7 @@ func OpenFile(filename string, opt ...Options) (*File, error) {
 // newFile is object builder
 func newFile() *File {
 	return &File{
+		options:          &Options{UnzipSizeLimit: UnzipSizeLimit},
 		xmlAttr:          make(map[string][]xml.Attr),
 		checked:          make(map[string]bool),
 		sheetMap:         make(map[string]string),
@@ -111,10 +119,13 @@ func OpenReader(r io.Reader, opt ...Options) (*File, error) {
 		return nil, err
 	}
 	f := newFile()
-	if bytes.Contains(b, oleIdentifier) && len(opt) > 0 {
-		for _, o := range opt {
-			f.options = &o
+	for i := range opt {
+		f.options = &opt[i]
+		if f.options.UnzipSizeLimit == 0 {
+			f.options.UnzipSizeLimit = UnzipSizeLimit
 		}
+	}
+	if bytes.Contains(b, oleIdentifier) {
 		b, err = Decrypt(b, f.options)
 		if err != nil {
 			return nil, fmt.Errorf("decrypted file failed")
@@ -124,8 +135,7 @@ func OpenReader(r io.Reader, opt ...Options) (*File, error) {
 	if err != nil {
 		return nil, err
 	}
-
-	file, sheetCount, err := ReadZipReader(zr)
+	file, sheetCount, err := ReadZipReader(zr, f.options)
 	if err != nil {
 		return nil, err
 	}
@@ -316,18 +326,18 @@ func (f *File) UpdateLinkedValue() error {
 	// recalculate formulas
 	wb.CalcPr = nil
 	for _, name := range f.GetSheetList() {
-		xlsx, err := f.workSheetReader(name)
+		ws, err := f.workSheetReader(name)
 		if err != nil {
 			if err.Error() == fmt.Sprintf("sheet %s is chart sheet", trimSheetName(name)) {
 				continue
 			}
 			return err
 		}
-		for indexR := range xlsx.SheetData.Row {
-			for indexC, col := range xlsx.SheetData.Row[indexR].C {
+		for indexR := range ws.SheetData.Row {
+			for indexC, col := range ws.SheetData.Row[indexR].C {
 				if col.F != nil && col.V != "" {
-					xlsx.SheetData.Row[indexR].C[indexC].V = ""
-					xlsx.SheetData.Row[indexR].C[indexC].T = ""
+					ws.SheetData.Row[indexR].C[indexC].V = ""
+					ws.SheetData.Row[indexR].C[indexC].T = ""
 				}
 			}
 		}
@@ -381,7 +391,7 @@ func (f *File) AddVBAProject(bin string) error {
 			Type:   SourceRelationshipVBAProject,
 		})
 	}
-	file, _ := ioutil.ReadFile(bin)
+	file, _ := ioutil.ReadFile(filepath.Clean(bin))
 	f.Pkg.Store("xl/vbaProject.bin", file)
 	return err
 }
diff --git a/excelize_test.go b/excelize_test.go
index cc3a1b2..918279b 100644
--- a/excelize_test.go
+++ b/excelize_test.go
@@ -184,13 +184,9 @@ func TestSaveFile(t *testing.T) {
 
 func TestSaveAsWrongPath(t *testing.T) {
 	f, err := OpenFile(filepath.Join("test", "Book1.xlsx"))
-	if assert.NoError(t, err) {
-		// Test write file to not exist directory.
-		err = f.SaveAs("")
-		if assert.Error(t, err) {
-			assert.True(t, os.IsNotExist(err), "Error: %v: Expected os.IsNotExists(err) == true", err)
-		}
-	}
+	assert.NoError(t, err)
+	// Test write file to not exist directory.
+	assert.EqualError(t, f.SaveAs(""), "open .: is a directory")
 }
 
 func TestCharsetTranscoder(t *testing.T) {
@@ -204,6 +200,10 @@ func TestOpenReader(t *testing.T) {
 	_, err = OpenReader(bytes.NewReader(oleIdentifier), Options{Password: "password"})
 	assert.EqualError(t, err, "decrypted file failed")
 
+	// Test open spreadsheet with unzip size limit.
+	_, err = OpenFile(filepath.Join("test", "Book1.xlsx"), Options{UnzipSizeLimit: 100})
+	assert.EqualError(t, err, newUnzipSizeLimitError(100).Error())
+
 	// Test open password protected spreadsheet created by Microsoft Office Excel 2010.
 	f, err := OpenFile(filepath.Join("test", "encryptSHA1.xlsx"), Options{Password: "password"})
 	assert.NoError(t, err)
@@ -1226,6 +1226,7 @@ func TestWorkSheetReader(t *testing.T) {
 	f.Pkg.Store("xl/worksheets/sheet1.xml", MacintoshCyrillicCharset)
 	_, err := f.workSheetReader("Sheet1")
 	assert.EqualError(t, err, "xml decode error: XML syntax error on line 1: invalid UTF-8")
+	assert.EqualError(t, f.UpdateLinkedValue(), "xml decode error: XML syntax error on line 1: invalid UTF-8")
 
 	// Test on no checked worksheet.
 	f = NewFile()
diff --git a/file.go b/file.go
index abb0305..bfb6abf 100644
--- a/file.go
+++ b/file.go
@@ -17,6 +17,7 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"path/filepath"
 	"sync"
 )
 
@@ -69,14 +70,14 @@ func (f *File) SaveAs(name string, opt ...Options) error {
 		return ErrMaxFileNameLength
 	}
 	f.Path = name
-	file, err := os.OpenFile(name, os.O_WRONLY|os.O_TRUNC|os.O_CREATE, 0666)
+	file, err := os.OpenFile(filepath.Clean(name), os.O_WRONLY|os.O_TRUNC|os.O_CREATE, 0600)
 	if err != nil {
 		return err
 	}
 	defer file.Close()
 	f.options = nil
-	for _, o := range opt {
-		f.options = &o
+	for i := range opt {
+		f.options = &opt[i]
 	}
 	return f.Write(file)
 }
@@ -102,7 +103,8 @@ func (f *File) WriteTo(w io.Writer) (int64, error) {
 	return 0, nil
 }
 
-// WriteToBuffer provides a function to get bytes.Buffer from the saved file. And it allocate space in memory. Be careful when the file size is large.
+// WriteToBuffer provides a function to get bytes.Buffer from the saved file,
+// and it allocates space in memory. Be careful when the file size is large.
 func (f *File) WriteToBuffer() (*bytes.Buffer, error) {
 	buf := new(bytes.Buffer)
 	zw := zip.NewWriter(buf)
@@ -130,7 +132,7 @@ func (f *File) WriteToBuffer() (*bytes.Buffer, error) {
 func (f *File) writeDirectToWriter(w io.Writer) error {
 	zw := zip.NewWriter(w)
 	if err := f.writeToZip(zw); err != nil {
-		zw.Close()
+		_ = zw.Close()
 		return err
 	}
 	return zw.Close()
@@ -157,14 +159,14 @@ func (f *File) writeToZip(zw *zip.Writer) error {
 		var from io.Reader
 		from, err = stream.rawData.Reader()
 		if err != nil {
-			stream.rawData.Close()
+			_ = stream.rawData.Close()
 			return err
 		}
 		_, err = io.Copy(fi, from)
 		if err != nil {
 			return err
 		}
-		stream.rawData.Close()
+		_ = stream.rawData.Close()
 	}
 	var err error
 	f.Pkg.Range(func(path, content interface{}) bool {
diff --git a/file_test.go b/file_test.go
index d86ce53..956ff92 100644
--- a/file_test.go
+++ b/file_test.go
@@ -37,9 +37,7 @@ func BenchmarkWrite(b *testing.B) {
 func TestWriteTo(t *testing.T) {
 	// Test WriteToBuffer err
 	{
-		f := File{}
-		buf := bytes.Buffer{}
-		f.Pkg = sync.Map{}
+		f, buf := File{Pkg: sync.Map{}}, bytes.Buffer{}
 		f.Pkg.Store("/d/", []byte("s"))
 		_, err := f.WriteTo(bufio.NewWriter(&buf))
 		assert.EqualError(t, err, "zip: write to directory")
@@ -47,9 +45,7 @@ func TestWriteTo(t *testing.T) {
 	}
 	// Test file path overflow
 	{
-		f := File{}
-		buf := bytes.Buffer{}
-		f.Pkg = sync.Map{}
+		f, buf := File{Pkg: sync.Map{}}, bytes.Buffer{}
 		const maxUint16 = 1<<16 - 1
 		f.Pkg.Store(strings.Repeat("s", maxUint16+1), nil)
 		_, err := f.WriteTo(bufio.NewWriter(&buf))
@@ -57,9 +53,7 @@ func TestWriteTo(t *testing.T) {
 	}
 	// Test StreamsWriter err
 	{
-		f := File{}
-		buf := bytes.Buffer{}
-		f.Pkg = sync.Map{}
+		f, buf := File{Pkg: sync.Map{}}, bytes.Buffer{}
 		f.Pkg.Store("s", nil)
 		f.streams = make(map[string]*StreamWriter)
 		file, _ := os.Open("123")
diff --git a/lib.go b/lib.go
index 912f738..712576d 100644
--- a/lib.go
+++ b/lib.go
@@ -26,15 +26,22 @@ import (
 
 // ReadZipReader can be used to read the spreadsheet in memory without touching the
 // filesystem.
-func ReadZipReader(r *zip.Reader) (map[string][]byte, int, error) {
-	var err error
-	var docPart = map[string]string{
-		"[content_types].xml":  "[Content_Types].xml",
-		"xl/sharedstrings.xml": "xl/sharedStrings.xml",
-	}
-	fileList := make(map[string][]byte, len(r.File))
-	worksheets := 0
+func ReadZipReader(r *zip.Reader, o *Options) (map[string][]byte, int, error) {
+	var (
+		err     error
+		docPart = map[string]string{
+			"[content_types].xml":  "[Content_Types].xml",
+			"xl/sharedstrings.xml": "xl/sharedStrings.xml",
+		}
+		fileList   = make(map[string][]byte, len(r.File))
+		worksheets int
+		unzipSize  int64
+	)
 	for _, v := range r.File {
+		unzipSize += v.FileInfo().Size()
+		if unzipSize > o.UnzipSizeLimit {
+			return fileList, worksheets, newUnzipSizeLimitError(o.UnzipSizeLimit)
+		}
 		fileName := strings.Replace(v.Name, "\\", "/", -1)
 		if partName, ok := docPart[strings.ToLower(fileName)]; ok {
 			fileName = partName
@@ -61,7 +68,7 @@ func (f *File) readXML(name string) []byte {
 }
 
 // saveFileList provides a function to update given file content in file list
-// of XLSX.
+// of spreadsheet.
 func (f *File) saveFileList(name string, content []byte) {
 	f.Pkg.Store(name, append([]byte(XMLHeader), content...))
 }
@@ -75,8 +82,7 @@ func readFile(file *zip.File) ([]byte, error) {
 	dat := make([]byte, 0, file.FileInfo().Size())
 	buff := bytes.NewBuffer(dat)
 	_, _ = io.Copy(buff, rc)
-	rc.Close()
-	return buff.Bytes(), nil
+	return buff.Bytes(), rc.Close()
 }
 
 // SplitCellName splits cell name to column name and row number.
diff --git a/merge_test.go b/merge_test.go
index a370126..02d92fb 100644
--- a/merge_test.go
+++ b/merge_test.go
@@ -148,16 +148,16 @@ func TestUnmergeCell(t *testing.T) {
 	}
 	sheet1 := f.GetSheetName(0)
 
-	xlsx, err := f.workSheetReader(sheet1)
+	sheet, err := f.workSheetReader(sheet1)
 	assert.NoError(t, err)
 
-	mergeCellNum := len(xlsx.MergeCells.Cells)
+	mergeCellNum := len(sheet.MergeCells.Cells)
 
 	assert.EqualError(t, f.UnmergeCell("Sheet1", "A", "A"), `cannot convert cell "A" to coordinates: invalid cell name "A"`)
 
 	// unmerge the mergecell that contains A1
 	assert.NoError(t, f.UnmergeCell(sheet1, "A1", "A1"))
-	if len(xlsx.MergeCells.Cells) != mergeCellNum-1 {
+	if len(sheet.MergeCells.Cells) != mergeCellNum-1 {
 		t.FailNow()
 	}
 
diff --git a/picture.go b/picture.go
index c37899e..e3601dd 100644
--- a/picture.go
+++ b/picture.go
@@ -94,7 +94,7 @@ func (f *File) AddPicture(sheet, cell, picture, format string) error {
 	if !ok {
 		return ErrImgExt
 	}
-	file, _ := ioutil.ReadFile(picture)
+	file, _ := ioutil.ReadFile(filepath.Clean(picture))
 	_, name := filepath.Split(picture)
 	return f.AddPictureFromBytes(sheet, cell, format, name, ext, file)
 }
@@ -199,8 +199,8 @@ func (f *File) deleteSheetRelationships(sheet, rID string) {
 // addSheetLegacyDrawing provides a function to add legacy drawing element to
 // xl/worksheets/sheet%d.xml by given worksheet name and relationship index.
 func (f *File) addSheetLegacyDrawing(sheet string, rID int) {
-	xlsx, _ := f.workSheetReader(sheet)
-	xlsx.LegacyDrawing = &xlsxLegacyDrawing{
+	ws, _ := f.workSheetReader(sheet)
+	ws.LegacyDrawing = &xlsxLegacyDrawing{
 		RID: "rId" + strconv.Itoa(rID),
 	}
 }
@@ -208,8 +208,8 @@ func (f *File) addSheetLegacyDrawing(sheet string, rID int) {
 // addSheetDrawing provides a function to add drawing element to
 // xl/worksheets/sheet%d.xml by given worksheet name and relationship index.
 func (f *File) addSheetDrawing(sheet string, rID int) {
-	xlsx, _ := f.workSheetReader(sheet)
-	xlsx.Drawing = &xlsxDrawing{
+	ws, _ := f.workSheetReader(sheet)
+	ws.Drawing = &xlsxDrawing{
 		RID: "rId" + strconv.Itoa(rID),
 	}
 }
@@ -217,8 +217,8 @@ func (f *File) addSheetDrawing(sheet string, rID int) {
 // addSheetPicture provides a function to add picture element to
 // xl/worksheets/sheet%d.xml by given worksheet name and relationship index.
 func (f *File) addSheetPicture(sheet string, rID int) {
-	xlsx, _ := f.workSheetReader(sheet)
-	xlsx.Picture = &xlsxPicture{
+	ws, _ := f.workSheetReader(sheet)
+	ws.Picture = &xlsxPicture{
 		RID: "rId" + strconv.Itoa(rID),
 	}
 }
diff --git a/picture_test.go b/picture_test.go
index 913ed3d..3e12f5f 100644
--- a/picture_test.go
+++ b/picture_test.go
@@ -71,24 +71,24 @@ func TestAddPicture(t *testing.T) {
 }
 
 func TestAddPictureErrors(t *testing.T) {
-	xlsx, err := OpenFile(filepath.Join("test", "Book1.xlsx"))
+	f, err := OpenFile(filepath.Join("test", "Book1.xlsx"))
 	assert.NoError(t, err)
 
 	// Test add picture to worksheet with invalid file path.
-	err = xlsx.AddPicture("Sheet1", "G21", filepath.Join("test", "not_exists_dir", "not_exists.icon"), "")
+	err = f.AddPicture("Sheet1", "G21", filepath.Join("test", "not_exists_dir", "not_exists.icon"), "")
 	if assert.Error(t, err) {
 		assert.True(t, os.IsNotExist(err), "Expected os.IsNotExist(err) == true")
 	}
 
 	// Test add picture to worksheet with unsupported file type.
-	err = xlsx.AddPicture("Sheet1", "G21", filepath.Join("test", "Book1.xlsx"), "")
+	err = f.AddPicture("Sheet1", "G21", filepath.Join("test", "Book1.xlsx"), "")
 	assert.EqualError(t, err, ErrImgExt.Error())
 
-	err = xlsx.AddPictureFromBytes("Sheet1", "G21", "", "Excel Logo", "jpg", make([]byte, 1))
+	err = f.AddPictureFromBytes("Sheet1", "G21", "", "Excel Logo", "jpg", make([]byte, 1))
 	assert.EqualError(t, err, ErrImgExt.Error())
 
 	// Test add picture to worksheet with invalid file data.
-	err = xlsx.AddPictureFromBytes("Sheet1", "G21", "", "Excel Logo", ".jpg", make([]byte, 1))
+	err = f.AddPictureFromBytes("Sheet1", "G21", "", "Excel Logo", ".jpg", make([]byte, 1))
 	assert.EqualError(t, err, "image: unknown format")
 }
 
diff --git a/sheet.go b/sheet.go
index 1c4b355..7e15bbe 100644
--- a/sheet.go
+++ b/sheet.go
@@ -480,7 +480,7 @@ func (f *File) SetSheetBackground(sheet, picture string) error {
 	if !ok {
 		return ErrImgExt
 	}
-	file, _ := ioutil.ReadFile(picture)
+	file, _ := ioutil.ReadFile(filepath.Clean(picture))
 	name := f.addMedia(file, ext)
 	sheetRels := "xl/worksheets/_rels/" + strings.TrimPrefix(f.sheetMap[trimSheetName(sheet)], "xl/worksheets/") + ".rels"
 	rID := f.addRels(sheetRels, SourceRelationshipImage, strings.Replace(name, "xl", "..", 1), "")
@@ -655,13 +655,13 @@ func (f *File) SetSheetVisible(name string, visible bool) error {
 		}
 	}
 	for k, v := range content.Sheets.Sheet {
-		xlsx, err := f.workSheetReader(v.Name)
+		ws, err := f.workSheetReader(v.Name)
 		if err != nil {
 			return err
 		}
 		tabSelected := false
-		if len(xlsx.SheetViews.SheetView) > 0 {
-			tabSelected = xlsx.SheetViews.SheetView[0].TabSelected
+		if len(ws.SheetViews.SheetView) > 0 {
+			tabSelected = ws.SheetViews.SheetView[0].TabSelected
 		}
 		if v.Name == name && count > 1 && !tabSelected {
 			content.Sheets.Sheet[k].State = "hidden"
diff --git a/sheetpr.go b/sheetpr.go
index 8bc4bfe..6f46040 100644
--- a/sheetpr.go
+++ b/sheetpr.go
@@ -182,14 +182,14 @@ func (o *AutoPageBreaks) getSheetPrOption(pr *xlsxSheetPr) {
 //   AutoPageBreaks(bool)
 //   OutlineSummaryBelow(bool)
 func (f *File) SetSheetPrOptions(name string, opts ...SheetPrOption) error {
-	sheet, err := f.workSheetReader(name)
+	ws, err := f.workSheetReader(name)
 	if err != nil {
 		return err
 	}
-	pr := sheet.SheetPr
+	pr := ws.SheetPr
 	if pr == nil {
 		pr = new(xlsxSheetPr)
-		sheet.SheetPr = pr
+		ws.SheetPr = pr
 	}
 
 	for _, opt := range opts {
@@ -208,11 +208,11 @@ func (f *File) SetSheetPrOptions(name string, opts ...SheetPrOption) error {
 //   AutoPageBreaks(bool)
 //   OutlineSummaryBelow(bool)
 func (f *File) GetSheetPrOptions(name string, opts ...SheetPrOptionPtr) error {
-	sheet, err := f.workSheetReader(name)
+	ws, err := f.workSheetReader(name)
 	if err != nil {
 		return err
 	}
-	pr := sheet.SheetPr
+	pr := ws.SheetPr
 
 	for _, opt := range opts {
 		opt.getSheetPrOption(pr)
diff --git a/stream.go b/stream.go
index 9939016..125b58c 100644
--- a/stream.go
+++ b/stream.go
@@ -346,8 +346,8 @@ func (sw *StreamWriter) SetRow(axis string, values []interface{}, opts ...RowOpt
 // marshalRowAttrs prepare attributes of the row by given options.
 func marshalRowAttrs(opts ...RowOpts) (attrs string, err error) {
 	var opt *RowOpts
-	for _, o := range opts {
-		opt = &o
+	for i := range opts {
+		opt = &opts[i]
 	}
 	if opt == nil {
 		return
diff --git a/xmlChartSheet.go b/xmlChartSheet.go
index 4ef2ded..fcc3443 100644
--- a/xmlChartSheet.go
+++ b/xmlChartSheet.go
@@ -5,9 +5,11 @@
 // struct code generated by github.com/xuri/xgen
 //
 // Package excelize providing a set of functions that allow you to write to
-// and read from XLSX files. Support reads and writes XLSX file generated by
-// Microsoft Excel™ 2007 and later. Support save file without losing original
-// charts of XLSX. This library needs Go version 1.15 or later.
+// and read from XLSX / XLSM / XLTM files. Supports reading and writing
+// spreadsheet documents generated by Microsoft Excel™ 2007 and later. Supports
+// complex components by high compatibility, and provided streaming API for
+// generating or reading data from a worksheet with huge amounts of data. This
+// library needs Go version 1.15 or later.
 
 package excelize
 
diff --git a/xmlDrawing.go b/xmlDrawing.go
index 4e35fcf..b49ae9d 100644
--- a/xmlDrawing.go
+++ b/xmlDrawing.go
@@ -94,6 +94,7 @@ const (
 
 // Excel specifications and limits
 const (
+	UnzipSizeLimit       = 1000 << 24
 	StreamChunkSize      = 1 << 24
 	MaxFontFamilyLength  = 31
 	MaxFontSize          = 409