Conversation
jarkko

Jarkko Sakkinen

Edited 1 year ago

I hope I got this right (safety-proprty), i.e. so that references are enforced to have equal life-time:

impl<'a> From<&'a Header> for &'a [u8] {
    fn from(value: &Header) -> Self {
        // SAFETY: out-of-boundary is not possible, given that the size constraint
        // exists in the struct definition. The lifetime parameter links the lifetime
        // of the header reference to the slice.
        unsafe { from_raw_parts((value as *const Header) as *const u8, size_of::<Header>()) }
    }
}

#rustlang

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Dr_Emann@hachyderm.io

Zachary Dremann

Reply to @jarkko

@jarkko I believe that's safe, provided Header has no padding, otherwise, you could have potentially uninitialized values for some of the bytes

You might be interested in `#[derive(AsBytes)]` from the zerocopy crate: https://docs.rs/zerocopy/latest/zerocopy/trait.AsBytes.html, which checks for that at compile time, and exposes a safe API

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jarkko

Jarkko Sakkinen

Reply to @Dr_Emann@hachyderm.io
@Dr_Emann thanks i took the advice and migrated! https://github.com/jarkkojs/zmodem2/commit/b374f24d9666ed7379b74047a556afc1a508cc55
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jarkko

Jarkko Sakkinen

Reply to @Dr_Emann@hachyderm.io
@Dr_Emann This was a good tip. I want to refactor this as a zero-copy thing overally but doing these primitives takes time because you really have to think through, I was going to add cast from bytes next. Saves time!
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Dr_Emann@hachyderm.io

Zachary Dremann

Reply to @jarkko

@jarkko 👍 awesome, glad I could help!

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jarkko

Jarkko Sakkinen

Reply to @Dr_Emann@hachyderm.io
@Dr_Emann Yeah, I was not doing that because I can but because I had to :-) Good lesson anyway with the type system, learned a lot even though the snippet is only few lines.
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