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Datatype storing a set of enum values as a 64-bit integer

EnumBitVector - Datatype storing a set of enum values as a 64-bit integer #

Motivation: #

Often we want to store a set of flags/labels. For examples which super powers a super hero has, what permissions a user has, or what labels a food item posesses. All those use cases can be represented by a set of enums:

enum SuperPowers { flying, speed, resistance, psychic, wealth}
batman.superPowers = {SuperPowers.wealth, SuperPowers.flying };

enum Permissions { deleteFiles, inviteOthers, createMeetings}
user1.permissions = { Permissions.inviteOthers };

enum FoodLabels {vegan, vegetarian, containsNuts, ketoFriendly}
carrotLabels = {FoodLabels.vegan, FoodLabels.vegetarian, FoodLabels.ketoFriendly};

If we store large quantities of data it could be inefficient to store these values as a List of Strings or even a Map of Strings to Booleans in json like this:

{
  "title": "carrot",
  "foodLabels": {
    "FoodLabels.vegan": true,
    "FoodLabels.vegetarian": true,
    "FoodLabels.containsNuts": false,
    "FoodLabels.ketoFriendly": true
  }
}

Instead, in Dart we could use a 64-bit integer to represent up to 64 boolean values: As long as our enum contains at most 64 values we can fit them all into one int, which can be represented as a hexadecimal string in just 8 characters.

Installation: #

dart pub add enum_bit_vector
dart pub get

Import the package:

import 'package:enum_bit_vector/enum_bit_vector.dart';

How to use: #

  1. Register the Enum Type you want to create EnumBitVectors for. This has to happen only once during the runtime of the program, but before you first use the data type anywhere.
EnumBitVector.registerEnum(SuperPowers.values);
  1. Create an EnumBitVector from a set or list of enums, an int or a hexString:
enumBitVector = EnumBitVector.fromSet({SuperPowers.flying, SuperPowers.resistance, SuperPowers.psychic});
enumBitVector = EnumBitVector.fromList([SuperPowers.flying, SuperPowers.resistance, SuperPowers.psychic]);
enumBitVector = EnumBitVector.fromInt(13); 
enumBitVector = EnumBitVector.fromHexString('0000000d');

Access values: #

you can easily convert an EnumBitVector to a set or list of enums, to an int or a hexString again, whenever needed:

enumBitVector.toSet() // => {SuperPowers.flying, SuperPowers.resistance, SuperPowers.psychic}
enumBitVector.enumSet // => {SuperPowers.flying, SuperPowers.resistance, SuperPowers.psychic}
enumBitVector.toList() // => [SuperPowers.flying, SuperPowers.resistance, SuperPowers.psychic]
enumBitVector.toInt() // => 13
enumBitVector.value // => 13
enumBitVector.toBinaryString()  // => '0000000000000000000000000000000000000000000000000000000001101';
enumBitVector.toHexString()  // => '0000000d';

JSON-conversion: #

final json = enumBitVector.toJson();
// json will be {'v': 13}
final bitVector = EnumBitVector<SuperPowers>.fromJson({'v': 13});
// will create a bitvector with int-value 13.
enumBitVector = EnumBitVector.fromSet({SuperPowers.flying, SuperPowers.resistance, SuperPowers.psychic});
print(enumBitVector);
// prints: EnumBitVector<SuperPowers>(0000000000000000000000000000000000000000000000000000000000001101 = {SuperPowers.flying, SuperPowers.resistance, SuperPowers.psychic})
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Datatype storing a set of enum values as a 64-bit integer

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