Announce Heptapod (#175)

_posts/2024-08-18-heptapod.md

@@ -0,0 +1,39 @@
+---
+title: 'Announcing Heptapod: Generate UUIDv7 in Haskell'
+---
+
+I'm happy to announce [Heptapod][1], a tiny Haskell library for generating version 7 UUIDs.
+If you're not familiar with UUIDv7s, they are defined by [RFC 9562][2].
+As a brief summary, they are sort of like a mix of UUIDv1s and UUIDv4s.
+They start with a timestamp and end with some randomness.
+Here's a diagram of their 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                             |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+```
+
+Heptapod allows you to generate UUIDv7s.
+`unix_ts_ms` comes from [`getSystemTime`][3].
+Both `rand_a` and `rand_b` both come from [`getEntropy`][4], which is cryptographically secure.
+
+The `rand_a` field can be a few different things: additional clock precision, a monotonic counter, or simply more randomness.
+Heptapod chooses the latter.
+If you'd like it to be something else, Heptapod also allows you to build your own UUIDv7 using provided values for `unix_ts_ms`, `rand_a`, and `rand_b`.
+
+That's it!
+Please check out [Heptapod][1] and consider using version 7 UUIDs!
+
+[1]: https://hackage.haskell.org/package/heptapod-1.0.0.0
+[2]: https://datatracker.ietf.org/doc/html/rfc9562
+[3]: https://hackage.haskell.org/package/time-1.14/docs/Data-Time-Clock-System.html#v:getSystemTime
+[4]: https://hackage.haskell.org/package/entropy-0.4.1.10/docs/System-Entropy.html#v:getEntropy