feat: add Substring function

strutil/string.go

@@ -281,3 +281,27 @@ func SplitEx(s, sep string, removeEmptyString bool) []string {
 
 	return ret
 }
+
+// Substring returns a substring of the specified length starting at the specified offset position.
+func Substring(s string, offset int, length uint) string {
+	rs := []rune(s)
+	size := len(rs)
+
+	if offset < 0 {
+		offset = size + offset
+		if offset < 0 {
+			offset = 0
+		}
+	}
+	if offset > size {
+		return ""
+	}
+
+	if length > uint(size)-uint(offset) {
+		length = uint(size - offset)
+	}
+
+	str := string(rs[offset : offset+int(length)])
+
+	return strings.Replace(str, "\x00", "", -1)
+}

strutil/string_example_test.go

@@ -337,3 +337,27 @@ func ExampleUnwrap() {
 	// foo*
 	// *foo*
 }
+
+func ExampleSubstring() {
+
+	result1 := Substring("abcde", 1, 3)
+	result2 := Substring("abcde", 1, 5)
+	result3 := Substring("abcde", -1, 3)
+	result4 := Substring("abcde", -2, 2)
+	result5 := Substring("abcde", -2, 3)
+	result6 := Substring("你好，欢迎你", 0, 2)
+
+	fmt.Println(result1)
+	fmt.Println(result2)
+	fmt.Println(result3)
+	fmt.Println(result4)
+	fmt.Println(result5)
+	fmt.Println(result6)
+	// Output:
+	// bcd
+	// bcde
+	// e
+	// de
+	// de
+	// 你好
+}

strutil/string_test.go

@@ -287,3 +287,14 @@ func TestSplitEx(t *testing.T) {
 	assert.Equal([]string{"a", "b", "c", ""}, SplitEx("a = b = c = ", " = ", false))
 	assert.Equal([]string{"a", "b", "c"}, SplitEx("a = b = c = ", " = ", true))
 }
+
+func TestSubstring(t *testing.T) {
+	assert := internal.NewAssert(t, "TestSubstring")
+
+	assert.Equal("bcd", Substring("abcde", 1, 3))
+	assert.Equal("bcde", Substring("abcde", 1, 5))
+	assert.Equal("e", Substring("abcde", -1, 3))
+	assert.Equal("de", Substring("abcde", -2, 2))
+	assert.Equal("de", Substring("abcde", -2, 3))
+	assert.Equal("你好", Substring("你好，欢迎你", 0, 2))
+}