mirror of https://git.sr.ht/~stygianentity/bincode
73 lines
2.3 KiB
Markdown
73 lines
2.3 KiB
Markdown
# Bincode
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<img align="right" src="./logo.png" />
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[](https://travis-ci.org/TyOverby/bincode)
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[](https://crates.io/crates/bincode)
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[](http://opensource.org/licenses/MIT)
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A compact encoder / decoder pair that uses an binary zero-fluff encoding scheme.
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The size of the encoded object will be the same or smaller than the size that
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the object takes up in memory in a running Rust program.
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In addition to exposing two simple functions that encode to Vec<u8> and decode
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from Vec<u8>, binary-encode exposes a Reader/Writer API that makes it work
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perfectly with other stream-based apis such as rust files, network streams,
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and the [flate2-rs](https://github.com/alexcrichton/flate2-rs) compression
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library.
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[Api Documentation](http://tyoverby.github.io/bincode/bincode/)
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## Example
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```rust
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extern crate bincode;
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extern crate rustc_serialize;
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use bincode::SizeLimit;
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use bincode::rustc_serialize::{encode, decode};
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#[derive(RustcEncodable, RustcDecodable, PartialEq)]
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struct Entity {
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x: f32,
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y: f32,
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}
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#[derive(RustcEncodable, RustcDecodable, PartialEq)]
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struct World {
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entities: Vec<Entity>
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}
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fn main() {
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let world = World {
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entities: vec![Entity {x: 0.0, y: 4.0}, Entity {x: 10.0, y: 20.5}]
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};
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let encoded: Vec<u8> = encode(&world, SizeLimit::Infinite).unwrap();
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// 8 bytes for the length of the vector, 4 bytes per float.
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assert_eq!(encoded.len(), 8 + 4 * 4);
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let decoded: World = decode(&encoded[..]).unwrap();
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assert!(world == decoded);
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}
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```
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## Details
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The encoding (and thus decoding) proceeds unsurprisingly -- primitive
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types are encoded according to the underlying `Writer`, tuples and
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structs are encoded by encoding their fields one-by-one, and enums are
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encoded by first writing out the tag representing the variant and
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then the contents.
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However, there are some implementation details to be aware of:
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* `isize`/`usize` are encoded as `i64`/`u64`, for portability.
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* enums variants are encoded as a `u32` instead of a `uint`.
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`u32` is enough for all practical uses.
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* `str` is encoded as `(u64, &[u8])`, where the `u64` is the number of
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bytes contained in the encoded string.
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