How do I get a multipart message as a &[u8]? Examples don't include it.

[Jaxkr]

Desired outcome: I want to pass a byte array to my function deserialize which takes a single &[u8] argument.

Currently, I do the following as a temporary measure because most messages are not multipart.

let msg: Multipart = msg?;
let data = msg.into_iter().next().unwrap();
let message_result = deserialize(&data);

I would like to get all members of the multipart message and combine them into a single byte array.

I tried copying the pull.rs example and modifying it to read:

msg.iter()
    .map(|item| item.as_slice())
    .collect::<Vec<&u8>>();

but I got the compiler error

error[E0658]: use of unstable library feature 'slice_pattern': stopgap trait for slice patterns
 --> src/transport/zeromq_incoming.rs:1:5
  |
1 | use core::slice::SlicePattern;
  |     ^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: see issue #56345 <https://github.com/rust-lang/rust/issues/56345> for more information

I've tried a couple other things and also noticed that the Deref impl for Message seems to return a reference to the underlying message byte array, but I couldn't figure out how to use it without running into a "doesn't have a size known at compile-time" error.

I've been banging my head against a wall for what feels like hours trying to figure this out, would massively appreciate your help. Thanks for this great library.

[Kobzol]

It seems that by modifying the example code, your IDE has auto-imported some part of stdlib that is currently unstable. You should remove that import from zeromq_incoming.rs:1. You probably tried to use as_slice, but that's not available on zmq::Message, to get a byte slice out of it, you need to use deref() (see below).

Each ZMQ multi-part message consists of several messages. You can get a byte slice (&[u8]) from each message easily using the Deref impl (by calling deref() on it). However, the slices of the individual messages are independent, so you cannot get a single [u8] slice out of them directly, because a slice has to be contiguous in memory.

If you want such a contiguous slice, the easiest solution is to go through the messages, collect them to a single Vec of bytes and then send that to your deserialize function:

let mut data = Vec::new();
for message in msg {
    data.extend_from_slice(message.deref());
}
let slice: &[u8] = data.as_slice();
deserialize(slice);

[Jaxkr]

Thank you. <3