get-size-derive

Derives [GetSize] for structs and enums.

The derive macro will provide a costum implementation of the [get_heap_size] method, which will simply call [get_heap_size] on all contained values and add the values up. This implies that all values contained in the struct or enum most implement the [GetSize] trait themselves.

When deriving [GetSize] for structs you can use the ignore attribute to make the derive macro ignore certain values. This might be usefull if some values do not implement the [GetSize] trait and do not have data on the heap, or if the data on the heap has already been accounted for somewhere else.

Example

```rust

[derive(GetSize)]

pub struct OwnStruct { value1: String, value2: u64, #[get_size(ignore)] value3: ExternalStruct, }

// Does not implement GetSize, so we ignore it. pub struct ExternalStruct { value1: u8, } ```

You can also derive [GetSize] on structs and enums with generics. In that case the generated trait implementation will require all generic types to also implement [GetSize].

This behavior may be unfavourable if one or more generic types are ignored duo to the corresponding struct field being ignored. In that case you can also use the ignore attribute at the struct level to specifiy the generic parameters which shall not be required to implement [GetSize] themselves.

Example

```rust use getsize::GetSize; use getsize_derive::*;

[derive(GetSize)]

[get_size(ignore(B, C))]

struct TestStructGenericsIgnore { value1: A, #[getsize(ignore)] value2: B, #[getsize(ignore)] value3: C, }

// Does not implement GetSize, so we ignore it. struct TestStructNoGetSize { value: String, }

fn main() { let no_impl = TestStructNoGetSize { value: "World!".into(), };

// If we did not ignore the C type, the following would not implement
// GetSize since C does not implement it.
let test: TestStructGenericsIgnore<String, u64, TestStructNoGetSize> = TestStructGenericsIgnore {
    value1: "Hello".into(),
    value2: 123,
    value3: no_impl,
};

assert_eq!(test.get_heap_size(), 5);

} ```

Panics

The derive macro will panic if used on unions since these are currently not supported. This might change in the future.

Note that there will be a compilation error if one of the (not ignored) values encountered does not implement the [GetSize] trait.

License

This library is licensed under the MIT license.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this library by you, shall be licensed as MIT, without any additional terms or conditions.