Optimize the coordinates conversion and some internal functions performance

chart.go

@@ -956,7 +956,7 @@ func (opts *Chart) parseTitle() error {
 // Set chart offset, scale, aspect ratio setting and print settings by 'Format',
 // same as function 'AddPicture'.
 //
-// Set the position of the chart plot area by 'PlotArea' field with
+// Set the properties of the chart plot area by 'PlotArea' field with
 // 'ChartPlotArea' data type. The properties that can be set are:
 //
 //	SecondPlotValues

excelize.go

@@ -311,15 +311,16 @@ func (f *File) workSheetReader(sheet string) (ws *xlsxWorksheet, err error) {
 		}
 	}
 	ws = new(xlsxWorksheet)
+	data := f.readBytes(name)
 	if attrs, ok := f.xmlAttr.Load(name); !ok {
-		d := f.xmlNewDecoder(bytes.NewReader(namespaceStrictToTransitional(f.readBytes(name))))
+		d := f.xmlNewDecoder(bytes.NewReader(namespaceStrictToTransitional(data)))
 		if attrs == nil {
 			attrs = []xml.Attr{}
 		}
 		attrs = append(attrs.([]xml.Attr), getRootElement(d)...)
 		f.xmlAttr.Store(name, attrs)
 	}
-	if err = f.xmlNewDecoder(bytes.NewReader(namespaceStrictToTransitional(f.readBytes(name)))).
+	if err = f.xmlNewDecoder(bytes.NewReader(namespaceStrictToTransitional(data))).
 		Decode(ws); err != nil && err != io.EOF {
 		return
 	}

lib.go

@@ -19,7 +19,6 @@ import (
 	"fmt"
 	"io"
 	"math"
-	"math/big"
 	"os"
 	"reflect"
 	"regexp"
@@ -225,6 +224,28 @@ func ColumnNameToNumber(name string) (int, error) {
 	return col, nil
 }
 
+// columnNames is a precomputed lookup table of column names for all valid
+// column numbers (1 to MaxColumns). This eliminates per-call allocations
+// in ColumnNumberToName.
+var columnNames = func() []string {
+	names := make([]string, MaxColumns+1)
+	for i := 1; i <= MaxColumns; i++ {
+		num := i
+		l := 0
+		for n := num; n > 0; n = (n - 1) / 26 {
+			l++
+		}
+		buf := make([]byte, l)
+		for num > 0 {
+			l--
+			buf[l] = byte((num-1)%26 + 'A')
+			num = (num - 1) / 26
+		}
+		names[i] = string(buf)
+	}
+	return names
+}()
+
 // ColumnNumberToName provides a function to convert the integer to Excel
 // sheet column title.
 //
@@ -235,18 +256,7 @@ func ColumnNumberToName(num int) (string, error) {
 	if num < MinColumns || num > MaxColumns {
 		return "", ErrColumnNumber
 	}
-	estimatedLength := 0
-	for n := num; n > 0; n = (n - 1) / 26 {
-		estimatedLength++
-	}
-
-	result := make([]byte, estimatedLength)
-	for num > 0 {
-		estimatedLength--
-		result[estimatedLength] = byte((num-1)%26 + 'A')
-		num = (num - 1) / 26
-	}
-	return string(result), nil
+	return columnNames[num], nil
 }
 
 // CellNameToCoordinates converts alphanumeric cell name to [X, Y] coordinates
@@ -282,14 +292,16 @@ func CoordinatesToCellName(col, row int, abs ...bool) (string, error) {
 	if row > TotalRows {
 		return "", ErrMaxRows
 	}
-	sign := ""
+	colName, err := ColumnNumberToName(col)
+	if err != nil {
+		return "", err
+	}
 	for _, a := range abs {
 		if a {
-			sign = "$"
+			return "$" + colName + "$" + strconv.Itoa(row), nil
 		}
 	}
-	colName, err := ColumnNumberToName(col)
-	return sign + colName + sign + strconv.Itoa(row), err
+	return colName + strconv.Itoa(row), nil
 }
 
 // rangeRefToCoordinates provides a function to convert range reference to a
@@ -573,6 +585,9 @@ func (ext *xlsxExt) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
 // namespaceStrictToTransitional provides a method to convert Strict and
 // Transitional namespaces.
 func namespaceStrictToTransitional(content []byte) []byte {
+	if !bytes.Contains(content, []byte("purl.oclc.org")) {
+		return content
+	}
 	namespaceTranslationDic := map[string]string{
 		StrictNameSpaceDocumentPropertiesVariantTypes: NameSpaceDocumentPropertiesVariantTypes.Value,
 		StrictNameSpaceDrawingMLMain:                  NameSpaceDrawingMLMain,
@@ -781,15 +796,12 @@ func isNumeric(s string) (bool, int, float64) {
 	if strings.Contains(s, "_") {
 		return false, 0, 0
 	}
-	var decimal big.Float
-	_, ok := decimal.SetString(s)
-	if !ok {
+	flt, err := strconv.ParseFloat(s, 64)
+	if err != nil {
 		return false, 0, 0
 	}
-	var noScientificNotation string
-	flt, _ := decimal.Float64()
-	noScientificNotation = strconv.FormatFloat(flt, 'f', -1, 64)
-	return true, len(strings.ReplaceAll(noScientificNotation, ".", "")), flt
+	noScientificNotation := strconv.FormatFloat(flt, 'f', -1, 64)
+	return true, len(noScientificNotation) - strings.Count(noScientificNotation, "."), flt
 }
 
 var (
@@ -809,6 +821,9 @@ var (
 // initial underscore shall itself be escaped (i.e. stored as _x005F_). For
 // example: The string literal _x0008_ would be stored as _x005F_x0008_.
 func bstrUnmarshal(s string) (result string) {
+	if !strings.Contains(s, "_x") {
+		return s
+	}
 	matches, l, cursor := bstrExp.FindAllStringSubmatchIndex(s, -1), len(s), 0
 	for _, match := range matches {
 		result += s[cursor:match[0]]