compact-rc 0.3.0

Low-memory reference-counting pointers
Documentation 
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# compact-rc
Low-memory reference-counting pointers.

The types in this crate have almost the same methods as standard `Rc` and `Arc`.
The differences from the standard type is as follows:

- Weak reference is not supported.
- Small integers can be used as refcount.

| Crate        | Strong count                       | Weak count    |
| ------------ | ---------------------------------- | ------------- |
| `std`        | `usize`                            | `usize`       |
| `compact-rc` | `u8`, `u16`, `u32`, `u64`, `usize` | not supported |

Due to the differences, some methods such as `weak_count` are not provided.

## Warnings
Using this crate with dynamically sized types (DSTs) like `Rc<str>` is not recommended.
Some implementations in this crate rely on unspecified layout of fat pointer.
So, DSTs may cause problems if the layout is changed in the future.

# Sample code
```rust
use compact_rc::Rc8;

fn main() {
    // rc1 is a pointer containing i8 value with u8 refcount.
    let rc1: Rc8<i8> = Rc8::new(100);

    assert_eq!(Rc8::strong_count(&rc1), 1);
    assert_eq!(*rc1, 100);

    // Increment the refcount.
    // The value is shared by rc1 and rc2.
    let rc2 = rc1.clone();

    assert_eq!(Rc8::strong_count(&rc1), 2);
    assert_eq!(Rc8::strong_count(&rc2), 2);
    assert_eq!(*rc1, 100);
    assert_eq!(*rc2, 100);
}
```