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use std::mem;
pub use heapsize_derive::*;
pub trait HeapSize {
/// Total number of bytes of heap memory owned by `self`.
///
/// Does not include the size of `self` itself, which may or may not be on
/// the heap. Includes only children of `self`, meaning things pointed to by
/// `self`.
fn heap_size_of_children(&self) -> usize;
}
//
// In a real version of this library there would be lots more impls here, but
// here are some interesting ones.
//
impl HeapSize for u8 {
/// A `u8` does not own any heap memory.
fn heap_size_of_children(&self) -> usize {
0
}
}
impl HeapSize for String {
/// A `String` owns enough heap memory to hold its reserved capacity.
fn heap_size_of_children(&self) -> usize {
self.capacity()
}
}
impl<T> HeapSize for Box<T>
where
T: ?Sized + HeapSize,
{
/// A `Box` owns however much heap memory was allocated to hold the value of
/// type `T` that we placed on the heap, plus transitively however much `T`
/// itself owns.
fn heap_size_of_children(&self) -> usize {
mem::size_of_val(&**self) + (**self).heap_size_of_children()
}
}
impl<T> HeapSize for [T]
where
T: HeapSize,
{
/// Sum of heap memory owned by each element of a dynamically sized slice of
/// `T`.
fn heap_size_of_children(&self) -> usize {
self.iter().map(HeapSize::heap_size_of_children).sum()
}
}
impl<'a, T> HeapSize for &'a T
where
T: ?Sized,
{
/// A shared reference does not own heap memory.
fn heap_size_of_children(&self) -> usize {
0
}
}
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