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Add a top level function to parity-util-mem #298

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Merged
ordian merged 4 commits into from
Jan 2, 2020
+16 −1
Merged

Add a top level function to parity-util-mem #298

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4cf98ff
add function
NikVolf Dec 31, 2019
5b2cb4f
Update parity-util-mem/src/lib.rs
NikVolf Jan 1, 2020
88c3cd4
Update parity-util-mem/src/lib.rs
NikVolf Jan 1, 2020
5175191
cargo fmt
NikVolf Jan 1, 2020
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17 changes: 16 additions & 1 deletion parity-util-mem/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -73,10 +73,17 @@ pub use malloc_size::{MallocSizeOf, MallocSizeOfOps};

pub use parity_util_mem_derive::*;

/// Heap size of structure.
///
/// Structure can be anything that implements MallocSizeOf.
pub fn malloc_size<T: MallocSizeOf + ?Sized>(t: &T) -> usize {
MallocSizeOf::size_of(t, &mut allocators::new_malloc_size_ops())
}

#[cfg(feature = "std")]
#[cfg(test)]
mod test {
use super::MallocSizeOfExt;
use super::{malloc_size, MallocSizeOf, MallocSizeOfExt};
use std::sync::Arc;

#[test]
Expand All @@ -85,4 +92,12 @@ mod test {
let s = val.malloc_size_of();
assert!(s > 0);
}

#[test]
fn test_dyn() {
trait Augmented: MallocSizeOf {}
impl Augmented for Vec<u8> {}
let val: Arc<dyn Augmented> = Arc::new(vec![0u8; 1024]);
assert!(malloc_size(&*val) > 1000);
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@ordian ordian Jan 1, 2020 •
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Does it actually use Arc in calculation? Dereference implies that it doesn't?

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@NikVolf NikVolf Jan 1, 2020

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No, it does not, it uses those of the dereferenced trait.

This is for cases when you know that Arc is the primary reference

MallocSizeOf is not defined for Arc<T: ?Sized>

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@ordian ordian Jan 1, 2020

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Hmm, measuring MallocSizeOf for an Arc is tricky, but I wonder why a type is required to be Sized for Arc (in MallocUnconditionalShallowSizeOf), but not for Box.

Anyway, my point was that using Arc in tests causes a bit of confusion, we can use a trait object here directly, something like

let val = vec![0u8; 1024];
let val_ref: &dyn Augmented = &val as _; 
assert!(malloc_size(val_ref) > 1000);

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@NikVolf NikVolf Jan 1, 2020

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I am also wondering about those constraints.

About the test, I only wanted to show how to measure Arc in the test, also to ensure the exactly Arc<dyn Trait> can be measured -- it is a higher-level requirement, so hope we can have it as it is.

}
}