A bitwise encoder/decoder similar to bincode.
We noticed relatively low entropy in data serialized with bincode. This library attempts to shrink the serialized size without sacrificing too much speed (as would be the case with compression).
Bitcode does not attempt to have a stable format, so we are free to optimize it.
#[derive(bitcode::Encode, bitcode::Decode)]#[bincode_hint(frequency = 123) to use Huffman coding#[bitcode_hint(expected_range = "50..100"]#[bitcode_hint(gamma)]#[bitcode(with_serde)]Aims to be no more than twice as slow as bincode or postcard. See rust serialization benchmark for benchmarks.
| Type | Bitcode (derive) | Bitcode (serde) | Bincode | Bincode (varint) | Postcard | |---------------------|------------------|-----------------|---------|------------------|----------| | bool | 1 | 1 | 8 | 8 | 8 | | u8 | 8 | 8 | 8 | 8 | 8 | | i8 | 8 | 8 | 8 | 8 | 8 | | u16 | 16 | 16 | 16 | 8-24 | 8-24 | | i16 | 16 | 16 | 16 | 8-24 | 8-24 | | u32 | 32 | 32 | 32 | 8-40 | 8-40 | | i32 | 32 | 32 | 32 | 8-40 | 8-40 | | u64 | 64 | 64 | 64 | 8-72 | 8-80 | | i64 | 64 | 64 | 64 | 8-72 | 8-80 | | f32 | 32 | 32 | 32 | 32 | 32 | | f64 | 64 | 64 | 64 | 64 | 64 | | char | 8-32 | 8-32 | 8-32 | 8-32 | 16-40 | | Option<()> | 1 | 1 | 8 | 8 | 8 | | Result<(), ()> | 1 | 1-3 | 32 | 8 | 8 | | enum { A, B, C, D } | 2 | 1-5 | 32 | 8 | 8 |
| Value | Bitcode (derive) | Bitcode (serde) | Bincode | Bincode (varint) | Postcard | |---------------------|------------------|-----------------|---------|------------------|----------| | [true; 4] | 4 | 4 | 32 | 32 | 32 | | vec![(); 0] | 1 | 1 | 64 | 8 | 8 | | vec![(); 1] | 3 | 3 | 64 | 8 | 8 | | vec![(); 256] | 17 | 17 | 64 | 24 | 16 | | vec![(); 65536] | 33 | 33 | 64 | 40 | 24 | | "" | 1 | 1 | 64 | 8 | 8 | | "abcd" | 37 | 37 | 96 | 40 | 40 | | "abcd1234" | 71 | 71 | 128 | 72 | 72 |
The following data structure was used for benchmarking.
```rust
struct Data {
x: Option
enum DataEnum {
Bar,
Baz(String),
Foo(Option
In the table below, **Size (bytes)** is the average size of a randomly generatedData` struct.
Zero Bytes are the percentage of bytes that are 0 in the output.
If the result contains a large percentage of zero bytes, that is a sign that it could be compressed more.
| Format | Size (bytes) | Zero Bytes | |------------------------|--------------|------------| | Bitcode (derive) | 6.5 | 0.28% | | Bitcode (serde) | 6.7 | 0.19% | | Bincode | 20.3 | 65.9% | | Bincode (varint) | 10.9 | 27.7% | | Bincode (LZ4) | 9.9 | 13.9% | | Bincode (Deflate Fast) | 8.4 | 0.88% | | Bincode (Deflate Best) | 7.8 | 0.29% | | Postcard | 10.7 | 28.3% | | ideal (max entropy) | | 0.39% |
When using serde to serialize enums. Enum variants are encoded such that variants declared earlier will occupy fewer bits. It is advantageous to sort variant declarations from most common to least common.
This limitation can be avoided by using bitcode's derive macros.
cargo install cargo-fuzz
cargo fuzz run fuzz
sudo apt install gcc-multilib
rustup target add i686-unknown-linux-gnu
cargo test --target i686-unknown-linux-gnu
Some test cases were derived from bincode (see comment in tests.rs).
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