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# codicon

Traits for encoding and decoding.

This crate provides generic traits for encoding and decoding to a
`std::io::Read` or `std::io::Write` type, respectively.

We often need to express that a type can be encoded or decoded. We
also need a way to express the type of the encoding or decoding as
well as parameters that may be used for that encoding or decoding.
This tiny crate solves this problem.

## Examples

Let's say we want `u8` to be able to be encoded in a (made up) format `Foo`
which simply writes the byte without modification. We can express this
encoding as follows:

```rust
use codicon::*;

struct Foo;

impl Encoder<Foo> for u8 {
    type Error = std::io::Error;

    fn encode(&self, mut writer: impl Write, params: Foo) -> std::io::Result<()> {
        writer.write_all(std::slice::from_ref(self))?;
        Ok(())
    }
}

let mut buf = [0u8; 1];
7u8.encode(&mut buf.as_mut(), Foo).unwrap();
assert_eq!(buf[0], 7u8);
```

Note that we used a unit struct because the `Foo` encoding doesn't take any
options. But if you wanted to specify encoding options, you could just make
a type with parameters.

Decoding works the same as encoding:

```rust
use codicon::*;

struct Foo;

impl Decoder<Foo> for u8 {
    type Error = std::io::Error;

    fn decode(mut reader: impl Read, params: Foo) -> std::io::Result<Self> {
        let mut byte = 0u8;
        reader.read_exact(std::slice::from_mut(&mut byte))?;
        Ok(byte)
    }
}

let buf = [7u8; 1];
assert_eq!(u8::decode(&mut buf.as_ref(), Foo).unwrap(), 7u8);
```

License: Apache-2.0