heapsize

A complete working Macros 1.1 implementation of a custom derive. Works on any Rust compiler >=1.15.0.

• heapsize/src/lib.rs
• heapsize_derive/src/lib.rs
• example/src/main.rs

We are deriving the HeapSize trait which computes an estimate of the amount of heap memory owned by a value.

pub trait HeapSize {
    /// Total number of bytes of heap memory owned by `self`.
    fn heap_size_of_children(&self) -> usize;
}

The custom derive allows users to write #[derive(HeapSize)] on data structures in their program.

#[derive(HeapSize)]
struct Demo<'a, T: ?Sized> {
    a: Box<T>,
    b: u8,
    c: &'a str,
    d: String,
}

The trait impl generated by the custom derive here would look like:

impl<'a, T: ?Sized + ::heapsize::HeapSize> ::heapsize::HeapSize for Demo<'a, T> {
    fn heap_size_of_children(&self) -> usize {
        0 + ::heapsize::HeapSize::heap_size_of_children(&self.a)
            + ::heapsize::HeapSize::heap_size_of_children(&self.b)
            + ::heapsize::HeapSize::heap_size_of_children(&self.c)
            + ::heapsize::HeapSize::heap_size_of_children(&self.d)
    }
}