A variable-length array, also called runtime-sized

Provides a variable-length array (VLA), also called variable-sized or runtime-sized.

It is an array data structure whose length is determined at run time (instead of at compile time).

The main purpose of VLAs is to simplify programming of numerical algorithms.

NOTE THAT

Unlike a dynamic array, a VLA cannot change its size, which is determined once, at the time of creation. But they may be more comfortable in use than static arrays, whose size must be known at compile time.

What is more, the VLA, provided by this crate in some cases is more efficient than std::vec::Vec. That's because of some optimizations and closeness to C++ arrays, allocated by malloc. That's why some methods are unsafe.

Creating arrays

use runtime_sized_array::Array;

let arr1: Array<i32> = Array::new(10).expect("cant' create new array");

let mut vec = vec![1,2,3];
let ptr = vec.as_mut_ptr();
let size = vec.len();
let arr2: Array<i32> = unsafe { Array::from_pointer(ptr, size) };

let arr3: Array<i32> = vec.into();

Iterating

use runtime_sized_array::Array;

let mut array : Array<i32> = vec![1,2,3].into();

// mutable iterator
for item in array.iter_mut() {
    *item += 1;
}

// immutable iterator
for item in array.iter() {
    println!("{item}");
}

// immutable iterator
for item in &array {
    println!("{item}");
}

// again mutable iterator
for item in &mut array {
    *item *= 0;
}

Access to elements

Safe access:

use runtime_sized_array::Array;

let mut arr: Array<i32> = vec![1,2,4].into();

// immutable access
assert_eq!(arr.try_get(1), Some(&2));
assert_eq!(arr.try_get(10), None);

// mutable access
*arr.try_get_mut(1).unwrap() = 5;
assert_eq!(arr.try_get_mut(10), None);

// alternative mutable access
assert_eq!(try_set(1, 5), Some(()));
assert_eq!(arr.try_set(10, 4), None);

// by brackets
arr[0] = 17;
assert_eq!(arr[0], 17);

Unsafe access:

use runtime_sized_array::Array;

let mut arr: Array<i32> = vec![1,2,4].into();

// immutable access
unsafe { assert_eq!(arr.get(1), &2) }
// arr.get(10) - undefined behaviour

unsafe { *arr.get_mut(1) = 2; }
// *arr.get_mut(10) == 4; - undefined behaviour

// alternative mutable access
unsafe { arr.set(1, 5); }
// arr.set(10, 4); - undefined behaviour

unsafe {
    *arr.get_mut_ptr(0) = 10;
    assert_eq!(*arr.get_ptr(0), 10)
}