zerovec

Zero-copy vector abstractions over byte arrays.

zerovec enable vectors of multibyte types to be backed by a byte array, abstracting away issues including memory alignment and endianness.

This crate has two main types:

• ZeroVec<T> for fixed-width types like u32
• VarZeroVec<T> for variable-width types like str

Both are intended as drop-in replacements for Vec<T> in Serde structs serialized with a format supporting a borrowed byte buffer, like Bincode. Clients upgrading from Vec to ZeroVec or VarZeroVec benefit from zero heap allocations when deserializing read-only data.

Performance

zerovec is designed for fast deserialization from byte buffers with zero memory allocations while minimizing performance regressions for common vector operations.

Benchmark results on x86_64:

| Operation | Vec<T> | zerovec | |---|---|---| | Deserialize vec of 100 u32 | 233.18 ns | 14.120 ns | | Compute sum of vec of 100 u32 (read every element) | 8.7472 ns | 10.775 ns | | Binary search vec of 1000 u32 50 times | 442.80 ns | 472.51 ns | | Deserialize vec of 100 strings | 7.3740 us* | 1.4495 us | | Count chars in vec of 100 strings (read every element) | 747.50 ns | 955.28 ns | | Binary search vec of 500 strings 10 times | 466.09 ns | 790.33 ns |

* This result is reported for Vec<String>. However, Serde also supports deserializing to Vec<&str>; this gives 1.8420 us, much faster than Vec<String> but a bit slower than zerovec.

The benches used to generate the above table can be found in the benches directory in the project repository.

Features

• serde: enables Serde Serialize/Deserialize impls for ZeroVec and VarZeroVec.

Examples

Serialize and deserialize a struct with ZeroVec and VarZeroVec with Bincode:

```rust use zerovec::{ZeroVec, VarZeroVec};

// This example requires the "serde" feature

[derive(serde::Serialize, serde::Deserialize)]

pub struct DataStruct<'s> { #[serde(borrow)] nums: ZeroVec<'s, u32>, #[serde(borrow)] strs: VarZeroVec<'s, String>, }

let data = DataStruct { nums: ZeroVec::fromaligned(&[211, 281, 421, 461]), strs: VarZeroVec::from(vec!["hello".tostring(), "world".tostring()]), }; let bincodebytes = bincode::serialize(&data) .expect("Serialization should be successful"); asserteq!(54, bincodebytes.len());

let deserialized: DataStruct = bincode::deserialize(&bincodebytes) .expect("Deserialization should be successful"); asserteq!(Some(211), deserialized.nums.first()); asserteq!(Some("world"), deserialized.strs.get(1)); assert!(matches!(deserialized.nums, ZeroVec::Borrowed())); ```

More Information

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