How to get address of a slice?

help
#1

How to convert slice to either *const () or usize?

&[ T ] -> *const ()

Of course, I understand it will downgrade fat pointer to slim one dropping length.
My use case is comparing addresses of two slices.

#2 
slice as *const _ as *const ()

...but there are various gotchas around comparing addresses around adjacent slices, ZSTs, slices of zero length, providence depending on the length, etc.

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#3

slice.as_ptr().cast::<()>()

Though why do you need *const ()?

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#4

Thanks!

#5

To compare address of a slice with address of a structure.

#6 
slice.as_ptr().cast::<()>()

That does not work for me:

no method named `as_ptr` found for reference `&T1` in the current scope

Why did it get so many thumbs up? Is that preferable method?
If so it seems it is less generic.

#7

If it’s the slice that contains the structure, a better way of expressing that is:

ptr::eq(&slice[0], structure)

And if it’s the structure that contains the slice, first of all that’s really weird and second of all do note that it’s only meaningful if the structure is #[repr(C)] or #[repr(transparent)] and contains the slice/array as its only field.

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#8

slice is not a slice in that code, Rust is telling you that it’s an &T1.

#9

Aha! Okay then slice as *const _ as *const () works for both slice and non slice.

#10

std::ptr::eq() is good thing, but it does not allow comparing addresses of references on different types

#11

Why are they different types in the first place though? That makes me suspicious of your code.

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#12

Why not? :smiley:

#13

Same data has several representations.

#14

Just for the sake of auditing, can you post the code then?

#15

I will share a link with you after publishing my crate to let you to criticize me.

Nice blog :sunglasses: Why not medium?

#16

I am going to a bomb shelter. Russians continue to destruct my city :frowning:

#17

Good luck. Although I am a neighbor of Russia, may there be no war in the world

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#18

It does work AFAICT: Rust Playground

Maybe your code testing it has slice of the wrong type? The error message mention &T1 and not &[…].

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#19

Well, the title of the thread is "address of a slice", and that's the method on slices for doing exactly what was requested: https://doc.rust-lang.org/nightly/std/primitive.slice.html#method.as_ptr

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#20

Incidentally, you can use std::slice::from_ref (or from_mut).

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