add utils of incr&decr for cache

client/cache/calc_utils.go

@@ -0,0 +1,83 @@
+package cache
+
+import (
+	"fmt"
+	"math"
+)
+
+func incr(originVal interface{}) (interface{}, error) {
+	switch val := originVal.(type) {
+	case int:
+		tmp := val + 1
+		if val > 0 && tmp < 0 {
+			return nil, fmt.Errorf("increment would overflow")
+		}
+		return tmp, nil
+	case int32:
+		if val == math.MaxInt32 {
+			return nil, fmt.Errorf("increment would overflow")
+		}
+		return val + 1, nil
+	case int64:
+		// if val == math.MaxInt64 {
+		// 	return nil, fmt.Errorf("increment would overflow")
+		// }
+		return val + 1, nil
+	case uint:
+		tmp := val + 1
+		if tmp < val {
+			return nil, fmt.Errorf("increment would overflow")
+		}
+		return tmp, nil
+	case uint32:
+		if val == math.MaxUint32 {
+			return nil, fmt.Errorf("increment would overflow")
+		}
+		return val + 1, nil
+	case uint64:
+		if val == math.MaxUint64 {
+			return nil, fmt.Errorf("increment would overflow")
+		}
+		return val + 1, nil
+	default:
+		return nil, fmt.Errorf("item val is not (u)int (u)int32 (u)int64")
+	}
+}
+
+func decr(originVal interface{}) (interface{}, error) {
+	switch val := originVal.(type) {
+	case int:
+		tmp := val - 1
+		if val < 0 && tmp > 0 {
+			return nil, fmt.Errorf("decrement would overflow")
+		}
+		return tmp, nil
+	case int32:
+		if val == math.MinInt32 {
+			return nil, fmt.Errorf("decrement would overflow")
+		}
+		return val - 1, nil
+	case int64:
+		if val == math.MinInt64 {
+			return nil, fmt.Errorf("decrement would overflow")
+		}
+		return val - 1, nil
+	case uint:
+		if val == 0 {
+			return nil, fmt.Errorf("decrement would overflow")
+		}
+		return val - 1, nil
+	case uint32:
+		if val == 0 {
+			return nil, fmt.Errorf("increment would overflow")
+		}
+		return val - 1, nil
+	case uint64:
+		if val == 0 {
+			return nil, fmt.Errorf("increment would overflow")
+		}
+		return val - 1, nil
+	default:
+		return nil, fmt.Errorf("item val is not (u)int (u)int32 (u)int64")
+	}
+}