achan1989
I want tidy code that creates an opcode from two pieces, and encodes it as a little endian binary. Where “the OGF occupies the upper 6 bits of the Opcode, and the OCF occupies the remaining 10 bits.” This code is almost what I want, except that the resulting binary is big endian:
def opcode_bin(ogf, ocf), do: <<ogf::6, ocf::10>>
<<16, 1>> = opcode_bin(4, 1)
# I want <<1, 16>>
The following works, but the intermediate step isn’t very elegant:
def opcode_bin(ogf, ocf) do
<<opcode::16>> = <<ogf::6, ocf::10>>
<<opcode::little-16>>
end
Is there a nicer way to accomplish this, maybe by specifying that I want little-endian output directly?
Where Next?
Trending in Questions
Other Trending Topics
Latest on Elixir Forum
Sponsor Spotlight
Catch errors, track performance, monitor hosts and more.
Categories:
Sub Categories:
Forums
Popular Tags
- #ecto
- #liveview
- #troubleshooting
- #learning-elixir
- #library
- #deployment
- #erlang
- #testing
- #genserver
- #mix
- #absinthe
- #remote-other
- #otp
- #plug
- #how-to-question
- #macros
- #postgres
- #elixirconf
- #channels
- #exunit
- #discussion
- #code-sync
- #podcasts
- #javascript
- #onsite
- #dialyzer
- #docker
- #authentication
- #umbrella
- #full-time-contract
- #podcasts-by-brainlid
- #ecto-query
- #ai
- #elixirconf-us
- #blog-post
- #elixir-ls
- #phoenix_html
- #iex
- #graphql
- #genstage
- #websockets
- #supervisor
- #advent-of-code
- #distillery
- #processes
- #api
- #forms
- #elixirconf-eu
- #metaprogramming
- #hex
Our Sponsors
Build Elixir applications with speed and confidence.
Supporting innovation across the BEAM ecosystem.
We build reliable cloud platforms for business-critical systems.
Error tracking, logs, uptime, and Just Enough APM. Built for developers.
Elixir, Erlang & BEAM conferences from Code Sync - join us in 2026!
Bringing learning, work and compliance together since 1987.
Producing high quality Elixir screencasts since 2017.
**Building the future of software with AI, trust, and human connection.**
The team behind Membrane, Popcorn, LiveDebugger. Available for hire.
Courses that'll move you from confusion to "Aha, now I get it!"
Showing Posts 1 to 5- Show Best Posts
- Show All (oldest first)
- Show All (newest first)
NobbZ
Perhaps using
Binary.<<</2.Something like
x = ogf <<< 10 ||| ocf; <<x::little-16>>.That way you don’t have to pack just for immediate unpacking.
Maybe you can even inline
xinto the binary, I’m never sure what’s possible within a binary literal, I use them to rarely for creating values.aziz
Careful with the
Bitwiseoperators.ogf <<< 10would only shift and not mask like<<ogf::6>>. Masking cuts off the extra bits. So as an expression it can be:I guess you’d agree that’s hardly more readable. Alternatively you could create a handy
swap16function that swaps its bytes. Then you can have everything in one line and the intent is clear as day.NobbZ
Trimming would have happened in the
little-16part. At least forogf, but indeed I’ve forgotten aboutocf(or did I just assume that data has been sanitizer already?)achan1989
Interesting. Where are the docs for that? I had no idea that was a thing.
NobbZ
Sorry, my fault, it was
Bitwise, notBinary… That is the kind of stuff that happens when one replies to technical topics while waiting for the train home…