serde-hashkey 0.4.2

Space efficient, in-memory serde serialization which supports hashing.
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# serde-hashkey

[<img alt="github" src="https://img.shields.io/badge/github-udoprog/serde--hashkey-8da0cb?style=for-the-badge&logo=github" height="20">](https://github.com/udoprog/serde-hashkey)
[<img alt="crates.io" src="https://img.shields.io/crates/v/serde-hashkey.svg?style=for-the-badge&color=fc8d62&logo=rust" height="20">](https://crates.io/crates/serde-hashkey)
[<img alt="docs.rs" src="https://img.shields.io/badge/docs.rs-serde--hashkey-66c2a5?style=for-the-badge&logoColor=white&logo=data:image/svg+xml;base64,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" height="20">](https://docs.rs/serde-hashkey)
[<img alt="build status" src="https://img.shields.io/github/workflow/status/udoprog/serde-hashkey/CI/main?style=for-the-badge" height="20">](https://github.com/udoprog/serde-hashkey/actions?query=branch%3Amain)

Serde-based in-memory key serialization which supports hashing.

This allows any serde-serializable type to be converted into a value which
implements `PartialEq`, `Eq`, `ParialOrd`, `Ord`, and `Hash`.

[Key] is useful because it allows for a form of type-erasure. Let's say you
want to build a generic in-memory key-value store where you want to store
arbitrary serde-serializable keys. This is typical for things like caches or
dependency injection frameworks.

<br>

### Usage

Add the following to your Cargo.toml:

```toml
[dependencies]
serde-hashkey = "0.4.2"
```

<br>

### Float policies

By default, [Key] can't include floating point types such as `f32` and
`f64`. Neither of these are [totally ordered nor hashable].

To enable the [Key] type to use `f32` and `f64` it can be constructed with a
specific float policy.

Available float policies are:
* [RejectFloat] - the default behavior when using [to_key].
* [OrderedFloat] - the behavior when using [to_key_with_ordered_float]. The
  `ordered-float` feature must be enabled to use this. The behavior is
  derived from the [`ordered-float` crate].

### Features

* `ordered-float` - Enables serializing floating point numbers through
  behavior derived from the [`ordered-float` crate]

<br>

### Examples

> You can run this example with `cargo run --example book`

```rust
use std::collections::HashMap;

use serde_derive::{Deserialize, Serialize};
use serde_hashkey::{from_key, to_key, Error, Key};

#[derive(Debug, PartialEq, Eq, Serialize, Deserialize)]
struct Author {
    name: String,
    age: u32,
}

#[derive(Debug, PartialEq, Eq, Serialize, Deserialize)]
struct Book {
    title: String,
    author: Author,
}

let book = Book {
    title: String::from("Birds of a feather"),
    author: Author {
        name: String::from("Noah"),
        age: 42,
    },
};

let key = to_key(&book)?;

let mut ratings = HashMap::new();
ratings.insert(key.clone(), 5);

println!("ratings: {:?}", ratings);

println!(
    "book as json (through key): {}",
    serde_json::to_string_pretty(&key)?
);

println!(
    "book as json (through original object): {}",
    serde_json::to_string_pretty(&book)?
);

```

[totally ordered nor hashable]: https://internals.rust-lang.org/t/f32-f64-should-implement-hash/5436
[Key]: https://docs.rs/serde-hashkey/0/serde_hashkey/enum.Key.html
[to_key]: https://docs.rs/serde-hashkey/0/serde_hashkey/fn.to_key.html
[RejectFloat]: https://docs.rs/serde-hashkey/0/serde_hashkey/enum.RejectFloat.html
[OrderedFloat]: https://docs.rs/serde-hashkey/0/serde_hashkey/enum.OrderedFloat.html
[to_key_with_ordered_float]: https://docs.rs/serde-hashkey/0/serde_hashkey/fn.to_key_with_ordered_float.html
[`ordered-float` crate]: https://docs.rs/ordered-float/2/ordered_float/

License: MIT/Apache-2.0