4 releases

0.2.3 Jul 13, 2021
0.2.2 May 11, 2021
0.2.1 May 11, 2021
0.2.0 Apr 19, 2021

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2K SLoC

zerovec crates.io

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.

This crate has two optional features: serde and yoke. serde allows serializing and deserializing zerovec's abstractions via serde, and yoke enables implementations of Yokeable from the yoke crate.

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:

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::from_aligned(&[211, 281, 421, 461]),
    strs: VarZeroVec::from(vec!["hello".to_string(), "world".to_string()]),
};
let bincode_bytes = bincode::serialize(&data)
    .expect("Serialization should be successful");
assert_eq!(54, bincode_bytes.len());

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

More Information

For more information on development, authorship, contributing etc. please visit ICU4X home page.

Dependencies

~97KB