rom_cache 0.0.13

A rust crate to cache ROM in memory like CPU caching RAM.
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<a name="readme-top"></a>

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<!-- PROJECT LOGO -->
<br />
<div align="center">
<h3 align="center">rom-cache</h3>
  <p align="center">
    A rust crate to cache ROM in RAM like CPU caches RAM.
    <br />
    <a href="https://docs.rs/rom_cache"><strong>Explore the docs »</strong></a>
    <br />
    <br />
    <a href="https://github.com/kingwingfly/rom-cache">View Demo</a>
    ·
    <a href="https://github.com/kingwingfly/rom-cache/issues">Report Bug</a>
    ·
    <a href="https://github.com/kingwingfly/rom-cache/issues">Request Feature</a>
  </p>
</div>



<!-- TABLE OF CONTENTS -->
<details>
  <summary>Table of Contents</summary>
  <ol>
    <li><a href="#import">Import</a></li>
    <li>
      <a href="#about-the-project">About The Project</a>
      <ul>
        <li><a href="#built-with">Built With</a></li>
      </ul>
    </li>
    <li><a href="#usage">Usage</a></li>
    <li><a href="#changelog">Changelog</a></li>
    <li><a href="#roadmap">Roadmap</a></li>
    <li><a href="#contributing">Contributing</a></li>
    <li><a href="#license">License</a></li>
    <li><a href="#contact">Contact</a></li>
    <li><a href="#acknowledgments">Acknowledgments</a></li>
  </ol>
</details>

<!-- IMPORT -->
## Import
```toml
[dependencies]
rom_cache = { version = "0.0.13" }
```

<!-- ABOUT THE PROJECT -->
## About The Project

A rust crate to cache ROM in memory like CPU caching RAM.

(Here, ROM is a misnomer, it actually means data stored in Secondary Storage, e.g. HDD, SSD, etc.)

Trait `Cacheable` is provided to enable user define how to `load` and `store` data in Secondary Storage.

`Cache` is the main entry of this crate, which consists of `CacheGroup`s. And `CacheGroup` consists of `CacheLine`s.

`Cache::get::<T>()` and `Cache::get_mut::<T>()` are provided to retrieve data from Cache and storage. LRU is used to choose the `CacheLine` for `T`.

1. get
- cache hit: return `CacheRef`
- cache busy: `CacheError::Busy`, LRU-chosen `CacheLine` is still being writting or reading so that unable to be evicted.
- cache locked: `CacheError::Locked`, cannot read `T` while writing.

2. get_mut
- cache hit: return `CacheMut`, and dereferencing `CacheMut` will set `CacheLine` dirty.
- cache busy: `CacheError::Busy`, cannot evict LRU-chosen `CacheLine` which is still being used.
- cache locked: `CacheError::Locked`, cannot write `T` while reading or writing.

Any **dirty** `CacheLine` will be written back (`Cacheable::store()`) to Secondary Storage when evicted or `Cache` dropped.

### Features

- `nightly`: enable `#![feature(trait_upcasting)]` to simplify the `Cacheable` trait. (Nightly Rust is needed)

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### Built With

* Rust
* Miri (Testing)
* Loom (Concurrency Testing)

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<!-- USAGE EXAMPLES -->
## Usage
### Example

```rust ignore
# use rom_cache::Cache;
// e.g 2-way set associative cache (8 sets/groups), 16 cache lines in total
let cache: Cache<8, 2> = Default::default();
cache.get::<isize>().unwrap();
cache.get::<String>().unwrap();
{
    let mut s = cache.get_mut::<String>().unwrap();
    cache.get::<u64>().unwrap();
    cache.get::<usize>().unwrap();
    *s = "".to_string();    // set dirty
}
{
    let s = cache.get::<String>().unwrap(); // other threads may evict `String` and it's stored,
                                            // this will load it back
    assert_eq!(*s, "");                     // The `load` result is `""`
}
```

_For more examples, please refer to the [Tests](https://github.com/kingwingfly/rom-cache/tree/dev/tests), [Example](https://github.com/kingwingfly/rom-cache/blob/dev/examples/example.rs) or [Documentation](https://docs.rs/rom_cache)_

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<!-- CHANGELOG -->
## Changelog

todo

[more detailed changelog](https://github.com/kingwingfly/rom-cache/blob/dev/CHANGELOG.md)

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<!-- ROADMAP -->
## Roadmap

- [x] allow concurrent access
- [x] auto load when getting
- [ ] benchmark

<!-- CONTRIBUTING -->
## Contributing

Contributions are what make the open source community such an amazing place to learn, inspire, and create. Any contributions you make are **greatly appreciated**.

If you have a suggestion that would make this better, please fork the repo and create a pull request. You can also simply open an issue with the tag "enhancement".
Don't forget to give the project a star! Thanks again!

1. Fork the Project
2. Create your Feature Branch (`git checkout -b feature/AmazingFeature`)
3. Commit your Changes (`git commit -m 'Add some AmazingFeature'`)
4. Push to the Branch (`git push origin feature/AmazingFeature`)
5. Open a Pull Request

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<!-- LICENSE -->
## License

Distributed under the MIT License. See `LICENSE.txt` for more information.

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<!-- CONTACT -->
## Contact

Louis - 836250617@qq.com

Project Link: [https://github.com/kingwingfly/rom-cache](https://github.com/kingwingfly/rom-cache)

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