I am happy to announce that we open-sourced PackedStructs.jl . Shamelessly copying from its README: PackedStructs.jl provides the @packed macro to annotate structs. These structs will pack together types which do not have a native size, i.e. a power-of-two byte size. This is especially useful when …

Hi, nice package and thanks for the mention of FieldFlags.jl! How does your package compare to the @bitfield macro from FieldFlags.jl? The intention of that macro is precisely this kind of packing :slight_smile: There’s an open issue for type annotations on fields, which I haven’t had the time to ta…

[image] Sukera: How does your package compare to the @bitfield macro from FieldFlags.jl ? I wondered the same. When we created the package around 2 years ago, we didn’t know about FieldFlags.jl. I only learned later about it and wanted to mention it. There is definitely the difference in the …

Well.. Claude certainly has a way of interpreting things in such a way that they don’t at all align with my own mental model of the package :sweat_smile: The summary by the LLM seems more like a dissection based on surface level words than what’s already being tracked in the issue tracker …

Hmm, Claude’s summary certainly matched my mental model of both packages. However, I never went through the complete code of FieldFlags.jl, so my mental modal seems to be biased, too. How would you phrase it? Claude might not learn from it, but I probably would. :slight_smile:

Well, the codebase was originally designed with the eventual extension to isbits typed fields in mind, that’s why the issue was created not long after the initial commit was made :slight_smile: It’s just that I prefer to have documentation about what works right now, without explicitly writing every…

[image] Sukera: I’m actually curious how you are handling it for things like that, where a type has internal padding? We haven’t used it for use cases where an external bit layout with specified internal padding needs to be used. We are using it to increase performance and save memory in opti…

Ah, it seems you’ve misunderstood me - I was referring to type annotations like this: struct Foo A::Int8 B::Int64 end @packed struct Bar C::Int7 D::Foo end Is this also supported, and how are you dealing with the internal padding in Foo if it is? This is the main reason why I have…

[image] Sukera: Is this also supported, and how are you dealing with the internal padding in Foo if it is? I deliberately let this unspecified. Currently, there is no reordering or merging done in these cases. Instead padding is always added at the end of one “group” as it is done natively in…

[image] PatrickHaecker: Currently, there is no reordering or merging done in these cases. Instead padding is always added at the end of one “group” as it is done natively in Julia (which you can observe in Foo) What do you mean by this, what is a group? I thought @packed would remove padding,…

[ANN] PackedStructs.jl

Package Announcements

matthias314 June 28, 2026, 12:52pm 7

The combination EmulatedBitIntegers.jl + PackedStructs.jl is somewhat related to the type PackedVector from SmallCollections.jl. See my post in the thread for EmulatedBitIntegers.jl.

Topic		Replies	Views
[ANN] FieldFlags.jl: Bitfield-like structs Package Announcements bitfields , bitpacking	7	518	June 20, 2023
[ANN] EmulatedBitIntegers.jl Package Announcements	13	519	June 30, 2026
Best way to save/read bytes in struct Performance struct	6	798	April 23, 2022
Packed struct Performance	2	1237	January 16, 2020
Union structs type tag memory layout Internals & Design	12	591	February 1, 2026

[ANN] PackedStructs.jl

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