add SubstrCount and test case.

README.md

@@ -1097,6 +1097,7 @@ func PrettyJSON(v any) (string, error)
 func RenderTemplate(input string, data any, fns template.FuncMap, isFile ...bool) string
 func RenderText(input string, data any, fns template.FuncMap, isFile ...bool) string
 func WrapTag(s, tag string) string
+func SubstrCount(s string, needle string, params ...uint64) (int, error)
 ```
 
 ### System Utils

strutil/strutil.go

@@ -4,6 +4,7 @@ package strutil
 import (
 	"bytes"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"strings"
 	"text/template"
@@ -88,3 +89,35 @@ func WrapTag(s, tag string) string {
 	}
 	return fmt.Sprintf("<%s>%s</%s>", tag, s, tag)
 }
+
+// SubstrCount returns the number of times the substr substring occurs in the s string.
+// Actually, it comes from strings.Count().
+// s The string to search in
+// substr The substring to search for
+// params[0] The offset where to start counting.
+// params[1] The maximum length after the specified offset to search for the substring.
+func SubstrCount(s string, substr string, params ...uint64) (int, error) {
+	larg := len(params)
+	hasArgs := larg != 0
+	if hasArgs && larg > 2 {
+		return 0, errors.New("too many parameters")
+	}
+	if !hasArgs {
+		return strings.Count(s, substr), nil
+	}
+	strlen := len(s)
+	offset := 0
+	end := strlen
+	if hasArgs {
+		offset = int(params[0])
+		if larg == 2 {
+			length := int(params[1])
+			end = offset + length
+		}
+		if end > strlen {
+			end = strlen
+		}
+	}
+	s = string([]rune(s)[offset:end])
+	return strings.Count(s, substr), nil
+}

strutil/strutil_test.go

@@ -34,6 +34,23 @@ func TestWrapTag(t *testing.T) {
 	assert.Eq(t, "<info>abc</info>", strutil.WrapTag("abc", "info"))
 }
 
+func TestSubstrCount(t *testing.T) {
+	s := "I'm fine, thank you, and you"
+	substr := "you"
+	res, err := strutil.SubstrCount(s, substr)
+	assert.NoErr(t, err)
+	assert.Eq(t, 2, res)
+	res1, err := strutil.SubstrCount(s, substr, 18)
+	assert.NoErr(t, err)
+	assert.Eq(t, 1, res1)
+	res2, err := strutil.SubstrCount(s, substr, 17, 100)
+	assert.NoErr(t, err)
+	assert.Eq(t, 1, res2)
+	res3, err := strutil.SubstrCount(s, substr, 16)
+	assert.NoErr(t, err)
+	assert.Eq(t, 2, res3)
+}
+
 func TestPrettyJSON(t *testing.T) {
 	tests := []any{
 		map[string]int{"a": 1},