box_any

A Box wrapper without generic type that allows dynamic dispatch / downcast but without using fat pointer.

Provides a dynamic box type BoxAny, which contains a Box<T> value. BoxAny is similar to Box but it doesn't use fat pointer to dynamic dispatch.

Benchmarks

In this benchmark bench we create a Vec container composed by 4 Vec with different types (u8, u16, u32, u64) and then we insert 1M integer for each Vec type (Vec<u8>, Vec<u16>, Vec<u32>, Vec<u64>). To do this we use and compare two different approach:

• dyn box (dyn Trait standard approach): we create a Vec container with type: Vec<Box<dyn Array>> and we use downcast + push method to insert 1M integer for each Vec type.
• box_any: we create a Vec container with type Vec<BoxAny> and we use BoxAny downcast + push method to insert 1M integer for each Vec type.

As we can see from the result, using BoxAny approach to downcast and fill each Vec is faster then using dyn Trait approach.

cargo bench
    Finished bench [optimized] target(s) in 0.03s
     Running unittests src/lib.rs (target/release/deps/box_any-d326196ff75eb72f)

running 1 test
test tests::test ... ignored

test result: ok. 0 passed; 0 failed; 1 ignored; 0 measured; 0 filtered out; finished in 0.00s

     Running benches/bench.rs (target/release/deps/bench-06d6896e0a110c0e)
dyn box checked         time:   [14.393 ms 14.410 ms 14.431 ms]
                        change: [-3.8738% -2.8496% -2.0529%] (p = 0.00 < 0.05)
                        Performance has improved.
Found 10 outliers among 100 measurements (10.00%)
  6 (6.00%) high mild
  4 (4.00%) high severe

box_any checked         time:   [5.5236 ms 5.6059 ms 5.7449 ms]
                        change: [-8.4525% -5.6854% -2.4171%] (p = 0.00 < 0.05)
                        Performance has improved.
Found 13 outliers among 100 measurements (13.00%)
  8 (8.00%) high mild
  5 (5.00%) high severe

box_any checked #2      time:   [4.2085 ms 4.2173 ms 4.2287 ms]
                        change: [-6.8000% -6.2270% -5.7308%] (p = 0.00 < 0.05)
                        Performance has improved.
Found 15 outliers among 100 measurements (15.00%)
  5 (5.00%) high mild
  10 (10.00%) high severe

Example

use std::any:: TypeId;
use box_any::BoxAny;

let box_u32 = Box::new(032);
let box_string = Box::new(String::from("Hello World"));
let box_any_u32: BoxAny = box_u32.clone().into();
let box_any_string: BoxAny = box_string.clone().into();
let box_any_vec: Vec<BoxAny> = vec![box_any_u32, box_any_string];
assert!(box_any_vec[1].is::<String>());
let string_2: &String = box_any_vec[1].downcast_ref::<String>().unwrap();
assert_eq!(string_2, box_string.as_ref());