Swift script to generate UUID version 7 in accordance with draft-ietf-uuidrev-rfc4122bis-14. Can generate about 4k/ms on a Release profile on my A16 Bionic.

UUIDv7.swift

/// License: Public Domain, or MIT License where Public Domain is not available

import Foundation

extension UUID {
    /// Implementation of UUIDv7 generator based on the specifications in draft-ietf-uuidrev-rfc4122bis-14
    ///
    /// UUIDv7 is generated without using any additional methods of Monotonicity Guarantees. (Section 6.2) As such, the UUID is accurate to the millisecond only.
    ///
    // Field and Bit Layout:
    // 0                   1                   2                   3
    // 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    // |                           unix_ts_ms                          |
    // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    // |          unix_ts_ms           |  ver  |       rand_a          |
    // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    // |var|                        rand_b                             |
    // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    // |                            rand_b                             |
    // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    public static func init_v7(timeAtGeneration: Date = Date()) -> UUID? {
        let unix_ts_ms = withUnsafeBytes(of: UInt64(timeAtGeneration.timeIntervalSince1970 * 1000).bigEndian, Array.init)
        
        var rand = [UInt8](repeating: 0, count: 10)
        
        guard errSecSuccess == SecRandomCopyBytes(kSecRandomDefault, rand.count, &rand) else {
            return nil
        }
        
        // ver
        rand[0] &= 0b00001111
        rand[0] |= 0b01110000
        
        // var
        rand[2] &= 0b00111111
        rand[2] |= 0b10000000
        
        let bytes = (
            unix_ts_ms[2], unix_ts_ms[3], unix_ts_ms[4], unix_ts_ms[5],
            unix_ts_ms[6], unix_ts_ms[7], rand[0], rand[1],
            rand[2], rand[3], rand[4], rand[5],
            rand[6], rand[7], rand[8], rand[9]
        )
        
        return UUID(uuid: bytes)
    }
}