Stack that allows users to allocate dynamically sized arrays.
The stack wraps a buffer of bytes that it uses as a workspace. Allocating an array takes a chunk of memory from the stack, which can be reused once the array is dropped.
alloc: enables the allocator api.
use core::mem::MaybeUninit;
use dynstack::{DynStack, StackReq};
// We allocate enough storage for 3 `i32` and 4 `u8`.
let mut buf = [MaybeUninit::uninit();
StackReq::new::<i32>(3)
.and(StackReq::new::<u8>(4))
.unaligned_bytes_required()];
let stack = DynStack::new(&mut buf);
{
// We can have nested allocations.
// 3×`i32`
let (array_i32, substack) = stack.make_with::<i32>(3, |i| i as i32);
// and 4×`u8`
let (mut array_u8, _) = substack.make_with::<u8>(4, |_| 0);
// We can read from the arrays,
assert_eq!(array_i32[0], 0);
assert_eq!(array_i32[1], 1);
assert_eq!(array_i32[2], 2);
// and write to them.
array_u8[0] = 1;
assert_eq!(array_u8[0], 1);
assert_eq!(array_u8[1], 0);
assert_eq!(array_u8[2], 0);
assert_eq!(array_u8[3], 0);
}
{
// We can also have disjoint allocations.
// 3×`i32`
let (mut array_i32, _) = stack.make_with::<i32>(3, |i| i as i32);
assert_eq!(array_i32[0], 0);
assert_eq!(array_i32[1], 1);
assert_eq!(array_i32[2], 2);
}
{
// or 4×`u8`
let (mut array_u8, _) = stack.make_with::<i32>(4, |i| i as i32 + 3);
assert_eq!(array_u8[0], 3);
assert_eq!(array_u8[1], 4);
assert_eq!(array_u8[2], 5);
assert_eq!(array_u8[3], 6);
}