make trim use cutset like trim_right/trim_left

vlib/builtin/string.v

@@ -590,30 +590,38 @@ pub fn (s string) trim_space() string {
 	return res
 }
 
-pub fn (s string) trim(c byte) string {
-	if s == '' {
-		return ''
+pub fn (s string) trim(cutset string) string {
+	if s.len == 0 || cutset.len == 0 {
+		return s
 	}
-	mut i := 0
-	for i < s.len && c == s[i] {
-		i++
+	cs_arr := cutset.bytes()
+	mut pos_left := 0
+	mut pos_right := s.len - 1
+	mut cs_match := true
+	for pos_left <= s.len && pos_right >= -1 && cs_match {
+		cs_match = false
+		if s[pos_left] in cs_arr {
+			pos_left++
+			cs_match = true
+		}
+		if s[pos_right] in cs_arr {
+			pos_right--
+			cs_match = true
+		}
+		if pos_left > pos_right {
+			return ''
+		}
 	}
-	mut res := s.right(i)
-	mut end := res.len - 1
-	for end >= 0 && c == res[end] {
-		end--
-	}
-	res = res.left(end + 1)
-	return res
+	return s.substr(pos_left, pos_right+1)
 }
 
 pub fn (s string) trim_left(cutset string) string {
 	if s.len == 0 || cutset.len == 0 {
 		return s
 	}
-	mut pos := 0
 	cs_arr := cutset.bytes()
-	for s[pos] in cs_arr {
+	mut pos := 0
+	for pos <= s.len && s[pos] in cs_arr {
 		pos++
 	}
 	return s.right(pos)
@@ -623,9 +631,9 @@ pub fn (s string) trim_right(cutset string) string {
 	if s.len == 0 || cutset.len == 0 {
 		return s
 	}
-	mut pos := s.len - 1
 	cs_arr := cutset.bytes()
-	for s[pos] in cs_arr {
+	mut pos := s.len - 1
+	for pos >= -1 && s[pos] in cs_arr {
 		pos--
 	}
 	return s.left(pos+1)