orx-fixed-vec 0.4.0

A fixed capacity vector with pinned elements.
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# orx-fixed-vec


A fixed capacity vector with pinned elements.

## Motivation


There might be various situations where pinned elements are helpful.

* It is somehow required for async code. Not being an expert in the subject, leaving this [blog](https://blog.cloudflare.com/pin-and-unpin-in-rust) for the interested.
* It is a requirement to make self-referential types possible.

This crate focuses more on the latter. Particularly, it aims to make it safely and conveniently possible to build **self-referential collections** such as linked list, tree or graph.

See [`PinnedVec`](https://crates.io/crates/orx-pinned-vec) for complete documentation.

`FixedVec` is one of the pinned vec implementations which can be wrapped by an [`ImpVec`](https://crates.io/crates/orx-imp-vec) and allow building self referential collections.

## Comparison with `SplitVec`


[`SplitVec`](https://crates.io/crates/orx-pinned-vec) is another `PinnedVec` implementation aiming the same goal but with different features. You may see the comparison in the table below.

| **`FixedVec`**                                                               | **`SplitVec`**                                                                   |
|------------------------------------------------------------------------------|----------------------------------------------------------------------------------|
| Implements `PinnedVec`.                                                      | Implements `PinnedVec`.                                                          |
| Requires a capacity while creating.                                          | Capacity is optional.                                                            |
| Cannot grow beyond capacity; panics when `push` is called at capacity.       | Can grow dynamically. Further, it provides detailed control on how it must grow. |
| It is just a wrapper around `std::vec::Vec`; hence, has similar performance. | Performs additional tasks to provide flexibility; hence, slightly slower.        |


## Pinned elements


```rust
use orx_fixed_vec::prelude::*;

let mut vec = FixedVec::new(100);

// push the first element
vec.push(42usize);
assert_eq!(vec, &[42]);

// let's get a pointer to the first element
let addr42 = &vec[0] as *const usize;

// let's push 99 new elements
for i in 1..100 {
    vec.push(i);
}

for i in 0..100 {
    assert_eq!(if i == 0 { 42 } else { i }, vec[i]);
}

// the memory location of the first element remains intact
assert_eq!(addr42, &vec[0] as *const usize);

// we can safely (using unsafe!) dereference it and read the correct value
assert_eq!(unsafe { *addr42 }, 42);

// the next push when `vec.is_full()` panics!
// vec.push(0);
```

## License


This library is licensed under MIT license. See LICENSE for details.