A cable(pointer) with a hook(header at address) at the end and a sized payload(array)
A pointer type for heap allocation, with some special features: - Stores an optional user specified header at address - Stashes the size of the data inline - A resizable array with bounds checking that requires just a pointer to use - Adds padding where necessary to maintain alignment for header, size, and elements.
Add this to your Cargo.toml:
toml
[dependencies]
cable = "0.1.1"
```rust
let mut data: Cable
for i in data.iter() { println!("{:?}", i); }
println!("Header: {:?}", data.header().unwrap());
println!("Footprint: {}", data.footprint());
The `Cable<T, H>` is useful in creating other heap objects.
Creating a simple dynamic storage with a length and capacity:
rust
let mut data: Cable
println!("Length: {}", data.header().unwrap());
println!("Footprint: {}", data.footprint());
The `Cable<T, H>` works well for nested structures when a small footprint is required:
rust
let mut x: Vec
x.push(Cable::with_capacity(8));
x[1][2] = 32;
x[1][5] = 19;
In this case the vector acts like a 2D array but each element can have a variable size.
This allows for compact data structures with proper bounds checking and a minimal footprint.
A struct can be used as a header for convenience:
rust
struct Info {
id: i32,
position: (f32, f32),
length: usize,
}
let mut x: Cable
A header may be omitted for brevity:
rust
let mut x: Cable
This pointer is safe as it always allocates at least mem::size_of::<usize>() bytes on the heap and will point to that allocation.
A cable has some special allocation features and considerations:
- Will allocate at least mem::size_of::<H>() + padding for usize + mem::size_of::<usize>() + padding for T.
- H can be zero-sized, in this case, such as when using the unit type H = () the header is not allocated.
- Can optionally allocate memory zeroed.
- Cost is minimal, most memory layout is determined at compile time.
- Resembles a Box<H> when payload is unallocated (although with at least an extra mem::size_of::<usize>() bytes, see into_boxed_header).
To be determined, will likely support in the future: - no-std - serde - custom allocator