Generate timebase UUID in swift

Everything you need to know about UUID

First of all what is UUID?

In software development as soon as we encounter assigning/fetching piece of data uniquely first thing that pops up in mind is UUID(universally unique identifier). so this is how wikipedia defines it.

A universally unique identifier (UUID) is an identifier standard used in software construction. A UUID is simply a 128-bit value. The meaning of each bit is defined by any of several variants.

Still not clear?

A UUID is a 16-octet (128-bit) number in with digit having hyphens in the form of, 8–4–4–4–12, which can be both unique and random 😎

ex: b99d95a0–20c5–11ea-a092–59756dff43fc

Types of UUID

1. Version 1 (date-time and MAC address)
2. Version 2 (date-time and MAC address, DCE security version)
3. Versions 3 and 5 (namespace name-based)
4. Version 4 (random)

For this article will only discuss about Version 1 and 4

Ok, let see what is the difference between these two

• Version 1: This generates a unique ID based on a network card MAC address and a timer. These IDs are easy to predict (given one, I might be able to guess another one) and can be traced back to your network card. It’s not recommended to create these.
• Version 4: These are generated from random (or pseudo-random) numbers. If you just need to generate a UUID, this is probably what you want.

So let create UUID in swift

1. UUID Version 4

By default in Swift/iOS UUID’s is version version 4, here is the apple documentation

A universally unique value that can be used to identify types, interfaces, and other items.
Initializes a new UUID with RFC 4122 version 4 random bytes.

so to create UUID version 4

let uuidToUse = UUID() 

2. UUID Version 1

Creating the version 1 type UUID is not straight forward, but version 1 are very helpful in sorting because they are time based. so the we can make C call to generate the version 1

func generateVersionOneAkaTimeBasedUUID() -> String? {
// figure out the sizes
let uuidSize = MemoryLayout<uuid_t>.size
let uuidStringSize = MemoryLayout<uuid_string_t>.size
// get some ram
let uuidPointer = UnsafeMutablePointer<UInt8>.allocate(capacity: uuidSize)
let uuidStringPointer = UnsafeMutablePointer<Int8>.allocate(capacity: uuidStringSize)
// do the work in C
uuid_generate_time(uuidPointer)
uuid_unparse(uuidPointer, uuidStringPointer)
// make a Swift string while we still have the C stuff
let uuidString = NSString(utf8String: uuidStringPointer) as String?
// avoid leaks
uuidPointer.deallocate()
uuidStringPointer.deallocate()
assert(uuidString != nil, "uuid (V1 style) failed")
return uuidString
}

Thank you for Reading the article ☺️

Reference

1. Stackoverflow- https://stackoverflow.com/questions/41232049/uuid-in-swift3-but-version-1-style-uuid
2. More about UUID- https://www.sohamkamani.com/blog/2016/10/05/uuid1-vs-uuid4/