- LimitMixedStringLen

utils/utils.go

@@ -238,23 +238,65 @@ func Base64DecodeMultiString(strs ...string) (decodedData [][]byte, err error) {
 	return decodedData, nil
 }
 
-func LimitStringLen(str string, maxLen int) (limitedStr string) {
-	if maxLen > 0 {
-		if strLen := len(str); strLen > maxLen {
-			str = str[:maxLen]
+// 只适合与纯英文的情况
+func LimitStringLen(str string, maxByteCount int) (limitedStr string) {
+	if maxByteCount > 0 {
+		if strLen := len(str); strLen > maxByteCount {
+			str = str[:maxByteCount]
 		}
 	}
 	return str
 }
 
-func LimitUTF8StringLen(str string, maxLen int) (limitedStr string) {
-	if maxLen > 0 {
-		if len(str) > maxLen {
+// 限制的是字符数，不是字节数
+func LimitUTF8StringLen(str string, maxRuneCount int) (limitedStr string) {
+	if maxRuneCount > 0 {
+		if len(str) > maxRuneCount {
 			runeList := []rune(str)
-			if len(runeList) > maxLen {
-				str = string(runeList[:maxLen])
+			if len(runeList) > maxRuneCount {
+				str = string(runeList[:maxRuneCount])
 			}
 		}
 	}
 	return str
 }
+
+// 限制的是字节数，正常处理乱码
+func LimitMixedStringLen(str string, maxByteCount int) (limitedStr string) {
+	if maxByteCount <= 0 {
+		return str
+	}
+	length := len(str)
+	if maxByteCount >= length {
+		return str
+	}
+	bs := []byte(str)[:maxByteCount]
+	bl := 0
+	for i := len(bs) - 1; i >= 0; i-- {
+		switch {
+		case bs[i] >= 0 && bs[i] <= 127:
+			return string(bs[:i+1])
+		case bs[i] >= 128 && bs[i] <= 191:
+			bl++
+		case bs[i] >= 192 && bs[i] <= 253:
+			cl := 0
+			switch {
+			case bs[i]&252 == 252:
+				cl = 6
+			case bs[i]&248 == 248:
+				cl = 5
+			case bs[i]&240 == 240:
+				cl = 4
+			case bs[i]&224 == 224:
+				cl = 3
+			default:
+				cl = 2
+			}
+			if bl+1 == cl {
+				return string(bs[:i+cl])
+			}
+			return string(bs[:i])
+		}
+	}
+	return ""
+}