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https://github.com/uatuko/swift-xid
A globally unique id generator
https://github.com/uatuko/swift-xid
swiftpm xid
Last synced: 5 days ago
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A globally unique id generator
- Host: GitHub
- URL: https://github.com/uatuko/swift-xid
- Owner: uatuko
- License: mit
- Created: 2022-06-11T07:25:11.000Z (over 2 years ago)
- Default Branch: main
- Last Pushed: 2023-08-09T06:40:40.000Z (over 1 year ago)
- Last Synced: 2023-08-09T08:08:15.367Z (over 1 year ago)
- Topics: swiftpm, xid
- Language: Swift
- Homepage:
- Size: 33.2 KB
- Stars: 1
- Watchers: 1
- Forks: 1
- Open Issues: 1
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# Swift Xid
[](https://raw.githubusercontent.com/uatuko/swift-xid/main/LICENSE)
A globally unique id generator.
> This is a swift implementation of the Golang package found at: [https://github.com/rs/xid](https://github.com/rs/xid)
Xid uses MongoDB Object ID algorighm[^1] to generate globally unique ids with base32 serialzation to produce shorter strings.
## Binary representation
```
+---+----+----+----+----+----+----+----+----+----+-----+-----+
| 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 |
+---+----+----+----+----+----+----+----+----+----+-----+-----+
\----- time -----/ \ machine id / \- pid -/ \--- counter ---/
```
- 4-byte value representing the seconds since the Unix epoch,
- 3-byte machine identifier,
- 2-byte process id, and
- 3-byte counter, starting with a random value.
The binary representation of the id is compatible with MongoDB's 12 bytes Object IDs.
The string representation is using base32hex (w/o padding)[^2] for better space efficiency when stored in string form (20 bytes). The hex variant of base32 is used to retain the
sortable property of the id.
## Features
- Size: 12 bytes (96 bits), smaller than UUID, larger than Twitter Snowflake[^3]
- Base32hex encoded by default (20 chars when transported as printable string, still sortable)
- Configuration free: there is no need to set a unique machine and/or data center id
- K-ordered
- Embedded time with 1 second precision
- Unicity guaranteed for 16,777,216 (24 bits) unique ids per second and per host/process
- Lock-free (unlike UUIDv1 and v2)
## Comparison
| Name | Binary Size | String Size | Features
|-------------|-------------|----------------|----------------
| [UUID] | 16 bytes | 36 chars | configuration free, not sortable
| [shortuuid] | 16 bytes | 22 chars | configuration free, not sortable
| [Snowflake] | 8 bytes | up to 20 chars | needs machine/DC configuration, needs central server, sortable
| [MongoID] | 12 bytes | 24 chars | configuration free, sortable
| xid | 12 bytes | 20 chars | configuration free, sortable
[UUID]: https://en.wikipedia.org/wiki/Universally_unique_identifier
[shortuuid]: https://github.com/stochastic-technologies/shortuuid
[Snowflake]: https://blog.twitter.com/2010/announcing-snowflake
[MongoID]: https://www.mongodb.com/docs/manual/reference/method/ObjectId/
## Usage
```swift
let id: String = NewXid() // or let id: Id = NewXid()
print(id)
// Output: caia5ng890f0tr46f690
```
```swift
var xid = Xid()
print(xid.next())
// Output: caia5ng890f0tr00hgtg
```
```swift
// Get embedded info
let id = xid.next()
id.time()
id.machineId()
id.pid()
id.counter()
// Access raw bytes
print(id.data as NSData)
// Output: {length = 12, bytes = 0x62a4a4a108481e0f9b83781f}
```
### Encoding and Decoding
The `Id` structure complies with `Codable` protocol and can be converted into and out of an external representation (e.g. JSON).
#### Decoding from JSON
```swift
struct User: Decodable {
var id: Id
var name: String
}
let data = """
{
"id": "caia5ng890f0tr00hgtg",
"name": "Jane Smith"
}
""".data(using: .utf8)!
let decoder = JSONDecoder()
let user = try decoder.decode(User.self, from: data)
print(user.id)
// Output: caia5ng890f0tr00hgtg
```
#### Encoding into JSON
```swift
struct User: Encodable {
var id: Id
var name: String
}
let user = User(id: NewXid(), name: "Jane Smith")
let encoder = JSONEncoder()
let data = try encoder.encode(user)
print(String(data: data, encoding: .utf8)!)
// Output: {"id":"caia5ng890f0tr00hgtg","name":"Jane Smith"}
```
[^1]: https://www.mongodb.com/docs/manual/reference/method/ObjectId/
[^2]: https://datatracker.ietf.org/doc/html/rfc4648#section-7
[^3]: https://blog.twitter.com/2010/announcing-snowflake