struct CSUUID

• CSUUID
• Struct
• Value
• Object

Overview

This struct wraps up a UUID that encodes a timestamp measured as seconds from the epoch (0001-01-01 00:00:00.0 UTC) observed at the location where the timestamp was generated, plus nanoseconds in the current second, plus 6 bytes for unique identification of the source -- this could be an IPV4 address with two null bytes, a MAC address, or some other sequence that will fit in 6 bytes.

Nanoseconds will fit in an Int32 (4 bytes), but seconds since the epoch will not. The current number of seconds leaks a short distance into a 5th byte, meaning that in this class, it has to be represented by an Int64. This is problematic because a UID allows for 16 bytes, so the use of 8 for seconds and 4 for nanoseconds leaves only 4 bytes for system identification. It also leaves three bytes in the UUID as zeros because 8 bytes for seconds is a lot of seconds.

One solution is to combine the seconds and the nanoseconds into a single Int64 number. This requires math operations to do efficiently: (seconds * 1000000000) + nanoseconds and then more math to extract the original numbers in order to reconstruct the original timestamp. This leaves 8 bytes for identification or other uniqueness information, which is lovely, but the math requirement is less lovely.

The other options is to truncate 2 bytes off of the seconds, storing 6 bytes of seconds data. This leaves 6 bytes for identification.

The current implementation chose option #2, as it is less work to generate a UUID if math is not involved.

+-------------+-----------------+------------+
| nanoseconds |     seconds     | identifier |
|    0..3     |      4..10      |   11..15   |
+-------------+-----------------+------------+

Defined in:

csuuid.cr

Constant Summary

VERSION = "0.1.1"

Constructors

• .new(seconds : Int64, nanoseconds : Int32, identifier : Slice(UInt8) | String | Nil = nil)
• .new(uuid : String)
• .new(uuid : UUID | CSUUID)
• .new(timestamp : Time, identifier : Slice(UInt8) | String | Nil = nil)
• .new(identifier : Slice(UInt8) | String | Nil = nil)

Instance Method Summary

• #seconds_and_nanoseconds : Tuple(Int64, Int32)

  This returns a tuple containing the seconds since the epoch as well as the nanoseconds in the current second for the UUID.

• #timestamp : Time

  Return a Time object representing the timestamp encoded into the UUID as local time.

• #to_s : String

  Return the String representation of the UUID.

• #utc : Time

  Return a Time object representing the timestamp encoded into the UUID as UTC time.

Constructor Detail

Instance Method Detail