fklement

fklement

Hello, I’m currently struggling with the following problem:

"(1609089402.655258) vcan0 136#000200000000002A\n(1609089402.655456) vcan0 13A#0000000000000028\n(1609089402.655651) vcan0 13F#000000050000002E\n(1609089402.655838) vcan0 164#0000C01AA8000004\n(1609089402.656030) vcan0 17C#0000000010000021\n(1609089402.656223) vcan0 18E#00006B\n(1609089402.656410) vcan0 1CF#80050000003C\n(1609089402.656763) vcan0 1DC#02000039\n(1609089402.656997) vcan0 183#0000000900001020\n(1609089402.657268) vcan0 143#6B6B00E0\n"
** (ArgumentError) non-alphabet digit found: "\n" (byte 10)
    (elixir 1.11.2) lib/base.ex:878: Base.dec16_upper/1
    (elixir 1.11.2) lib/base.ex:892: Base."-do_decode16/2-lbc$^0/2-2-"/2
    (elixir 1.11.2) lib/base.ex:890: Base.do_decode16/2
    (cannes 0.0.1) lib/dumper.ex:56: Cannes.Dumper.format_candump_string/1
    (elixir 1.11.2) lib/stream.ex:441: anonymous fn/4 in Stream.each/2
    (elixir 1.11.2) lib/stream.ex:1540: Stream.do_unfold/4
    (elixir 1.11.2) lib/stream.ex:1609: Enumerable.Stream.do_each/4
    (elixir 1.11.2) lib/enum.ex:3461: Enum.into/4

Maybe some background first. I want to process the output of candump in elixir. I’m using the porcelain library to spawn a process to execute the candump command. So far everything works fine, but I get the above error when the timestamps are very, very close to each other. If they differ in the 4th last digit, everything works fine. But when the difference is only in the 3rd last digit, the problem occurs.

My Cannes.Dumper.format_candump_string/1 function assumes one line of the console output e.g. like:
(1609089347.177315) vcan0 164#0000C01AA8000022
Now, if the messages follow each other too closely, the function will receive more than one line and therefore fail. Somehow the Stream.each gets more then a single console line. It forwards e.g.:
"(1609090018.715053) vcan0 18E#00007A\n(1609090018.715409) vcan0 294#040B0002CF5A000E\n(1609090018.715701) vcan0 21E#03E83745220601\n"

A pretty dumb and hacky way that came up in my mind is to simply reject all elements in the stream where more than one \n occurs. I already implemented it and it works, but this way I’m missing all those messages.

I’m not very familiar with using streams in elixir. So maybe there is a pretty simple solution that I’m just not aware of. Also I would like to know why Streams behave like this.
Can anyone help me with this?

Showing Posts 1 to 3

ouven

ouven

Hi, without knowing much about your use case, for me it sounds like you could use flat_map to split multi lines into several messages and reinject each into the stream.

al2o3cr

al2o3cr

If you have a stream of values that sometimes have more than one \n-delimited value, you can transform them to a stream that has them one at a time:

a = ["1\n", "2\n3\n", "4\n"]

iex(4)> Stream.flat_map(a, &String.split(&1, "\n", trim: true)) |> Enum.to_list()
["1", "2", "3", "4"]
fklement

fklement OP

Perfect. So simple :heart_eyes:
Thanks for your post.

— All posts loaded —

Where Next? Top

Trending in Questions Top

itzmidinesh
Hi all, I’m working on a Phoenix project where I need to make external HTTP requests and I’m trying to choose between Req and HTTPoison....
New
yarrichar
I’m very new to Elixir, so sorry if this is a silly question: I am wondering what happens to the mailbox of a process when the machine i...
New
pragdave
How do I tell Hologram not to escape HTML when substituting into templates? {Textile.render(@product.long_description)} escapes the HTM...
New
Fl4m3Ph03n1x
Background When trying to execute mix release on a Windows 11 machine for a Phoenix project I get the following error: * assembling mark...
New
rlipscombe
I’d like to create a file with 600 permissions (rw-------), but there’s a race condition if I create it and then change the permissions. ...
New
saleyn
Is there a way to import record definitions in the iex shell for pretty printing (similar to the rr command in the erl shell)? This woul...
New
rlipscombe
When I use Mix.install with a git dependency, using git@github.com:... how do I change the SSH identity used? I’ve got two Github accoun...
New

Other Trending Topics Top

dominicletz
Hey there, I haven’t seen a list of useful Elixir specific skills for the popular AI tools yet so I’m starting one here with my first. ...
New
raa-ziq
Hi everyone :waving_hand: I wanted to share something I’ve been building — NowBlind, a random chat app designed to help people discover ...
New
mudasobwa
I fully migrated to my own harness from Anthropic/Gemini and I think it’s time to share it. Welcome DSH, the DeepSeek Harness, fully writ...
New
KristerV
Hey. Is there anyone here who creates agents in their apps? Not talking about using agents, but creating them. I’m finding it pretty diff...
New
OndrejValenta
(I just needed to vent somewhere and LinkedIn is full of hope, or hype, I’m not sure which exactly) AI dream has many faces, but general...
New
kip
Localize is the next generation localisation library for Elixir. Think of it as ex_cldr version 3.0. The first version will be released ...
New

We're in Beta

About us Mission Statement

Options

Thread Display Mode




Thread Preview

Skip Thread Previews