Add extract alfanumeric with selected special characters (#4)

* add extract alfanumeric with selected special characters

* fix comment

str/string.go

@@ -29,6 +29,21 @@ func ExtractAlfaNumericFromText(source string) string {
 	return result.String()
 }
 
+func ExtractAlfaNumericWithSelectedSpecialCharactersFromText(source string) string {
+	// allowed special characters are !"#$%&'()*+,-./ \[]\n
+	var result strings.Builder
+	for i := 0; i < len(source); i++ {
+		b := source[i]
+		if (32 <= b && b <= 57) ||
+			(65 <= b && b <= 93) ||
+			(97 <= b && b <= 122) ||
+			b == 10 {
+			result.WriteByte(b)
+		}
+	}
+	return result.String()
+}
+
 func SplitOnNotEmpty(str string, delimiter string) []string {
 	if strings.TrimSpace(str) != "" {
 		var result []string

str/string_test.go

@@ -0,0 +1,13 @@
+package str
+
+import (
+	"github.com/stretchr/testify/assert"
+	"testing"
+)
+
+func TestExtractAlfaNumericWithSelectedSpecialCharactersFromText(t *testing.T) {
+	sourceText := "Ab9 \\!@#$%^&*_+-=\n"
+	validateText := "Ab9 \\!#$%&*+-\n"
+	filteredText := ExtractAlfaNumericWithSelectedSpecialCharactersFromText(sourceText)
+	assert.Equal(t, validateText, filteredText)
+}