2 releases
0.1.1 | May 8, 2024 |
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0.1.0 | May 7, 2024 |
#697 in Procedural macros
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unsafe-access
A collection of Rust procedural macros designed to simplify the use of unsafe array indexing while maintaining traditional indexing semantics. These macros are especially beneficial in performance-critical areas where bounds-checking can be explicitly bypassed, assuming prior validation. The key feature is retaining standard array indexing syntax while skipping bounds checks, which can yield significant performance benefits.
Macros
unchecked_indices_ref
,unchecked_indices_clone
,unchecked_indices_copy
. These macros let the user access array elements viaget_unchecked
in a limited scope. This isunsafe
code.
use unsafe_access::unchecked_indices_copy;
let array = [1, 2, 3, 4, 5, 6];
let indices = [0, 3, 5];
let copied_array: [i32; 3] = unchecked_indices_copy! {
[
array[indices[0]],
array[indices[1]],
array[indices[2]],
]
};
unsafe_access_fn
An attribute macro that transforms standard array indexing within a function into unsafe, unchecked array indexing. This macro ensures that all indexing operations inside the function are converted to useget_unchecked
. This example can be found inexamples/matrices.rs
:
use unsafe_access::unsafe_access_fn;
const MATRIX_SIZE: usize = 100;
const QUERY_SIZE: usize = 5;
fn main() {
let matrix: [u64; MATRIX_SIZE * MATRIX_SIZE] = core::array::from_fn(|i| i as u64);
let indices: [usize; QUERY_SIZE] = core::array::from_fn(|_| rand::random::<usize>() % (MATRIX_SIZE * MATRIX_SIZE));
let result = unsafe { prechecked_indices(&matrix, &indices) };
println!("result: {result:?}");
}
#[unsafe_access_fn]
unsafe fn prechecked_indices<T: Copy, const N: usize>(array: &[T], indices: &[usize; N]) -> [T; N] {
core::array::from_fn(|i| array[indices[i]])
}
To run the example, execute:
cargo run --example matrices
Benchmarks
For a simple benchmark using random accesses, see benches/access.rs
, or via
cargo bench
Dependencies
~1.5MB
~38K SLoC