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# bzipper

[`bzipper`](https://crates.io/crates/bzipper) is a binary (de)serialiser for the Rust language.

Contrary to [Serde](https://crates.io/crates/serde/)/[Bincode](https://crates.io/crates/bincode/), the goal of this crate is to serialise data with a known size limit.
Therefore, this crate may be more suited for networking or other cases where a fixed-sized buffer is needed.

Keep in mind that this project is still work-in-progress.

This crate does not require any dependencies at the moment.
It is also compatible with `no_std`.

See [Docs.rs](https://docs.rs/bzipper/latest/bzipper/) for documentation.

## Data Model

Most primitive types serialise losslessly, with the exception being `usize` and `isize`.
These serialise as `u16` and `i16`, respectively, for portability reasons.

Unsized types, such as `str` and slices, are not supported.
Instead, array should be used.
For strings, the `FixedString` type is also provided.

## Usage

This crate revolves around the `Serialise` and `Deserialise` traits, both of which work around streams (more specifically, d-streams and s-streams).

Many core types come implemented with `bzipper`, including primitives as well as some standard library types such as `Option` and `Result`.

### Serialisation

To serialise an object implementing `Serialise`, simply allocate a so-called "s-stream" (short for *serialisation stream*) with the `Sstream` type:

```rs
let mut buf: [u8; 16] = Default::default();

let mut stream = bzipper::Sstream::new(&mut buf);
```

The resulting stream is immutable in the sense that it cannot grow its buffer, altough it does keep track of the buffer's state.

A byte sequence can be added to our new stream by passing the stream to a call to the `serialise` method:

```rs
use bzipper::Serialise;

let mut buf: [u8; 2] = Default::default();
let mut stream = bzipper::Sstream::new(&mut buf);

0x4554_u16.serialise(&mut stream).unwrap();
```

The ammount of bytes used by the serialiser (that is, the ammount of bytes written to the stream) is indicated by its return value (i.e. it has the type `Result<usize, Serialise::Error>`).

Whilst the *maximum* ammount of bytes is specified by the `SERIALISE_LIMIT` constant, this can in cases be lower (for example with `None` variants which are always encoded as a single, null byte).

When serialising primitives, the resulting byte stream is in big endian (a.k.a. network endian).
It is recommended for implementors to adhere to this convention as well.

After serialisation, the s-stream records the new write-to position of the buffer. This allows for *chaining* of serialisations, which can prove useful when implementing the trait for custom types.

### Deserialisation

As with serialisation, deserialisation uses streams (just with the `Dstream` type; short for *deserialisation stream*):

```rs
let data = [0x45, 0x54];

let mut stream = bzipper::Dstream::new(&data);
```

Using these streams is also just as simple as with s-streams:

```rs
use bzipper::Deserialise;

let data = [0x45, 0x54];
let mut stream = bzipper::Dstream::new(&data);

assert_eq!(u16::deserialise(&mut stream).unwrap(), 0x4554);
```

When chaining serialisations, keep in mind that appropriate deserialisations should come in **reverse order** (streams function similarly to stacks in this sense).

## Copyright & Licensing

Copyright 2024 Gabriel Bjørnager Jensen.

This program is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this program. If not, see <https://www.gnu.org/licenses/>.