Fix performance regression in v2.9.0, reduce trim cell value memory allocation for blank cells (#2100)

Author: artur-chopikian

cell.go

@@ -12,7 +12,6 @@
 package excelize
 
 import (
-	"bytes"
 	"encoding/xml"
 	"fmt"
 	"math"
@@ -510,13 +509,6 @@ func trimCellValue(value string, escape bool) (v string, ns xml.Attr) {
 	if utf8.RuneCountInString(value) > TotalCellChars {
 		value = string([]rune(value)[:TotalCellChars])
 	}
-	if escape && value != "" {
-		var buf bytes.Buffer
-		enc := xml.NewEncoder(&buf)
-		_ = enc.EncodeToken(xml.CharData(value))
-		_ = enc.Flush()
-		value = buf.String()
-	}
 	if value != "" {
 		prefix, suffix := value[0], value[len(value)-1]
 		for _, ascii := range []byte{9, 10, 13, 32} {
@@ -528,6 +520,12 @@ func trimCellValue(value string, escape bool) (v string, ns xml.Attr) {
 				break
 			}
 		}
+
+		if escape {
+			var buf strings.Builder
+			_ = xml.EscapeText(&buf, []byte(value))
+			value = strings.ReplaceAll(buf.String(), "
", "\n")
+		}
 	}
 	v = bstrMarshal(value)
 	return