macro persia-speedy-derive

A fast binary serialization framework, #[derive(Readable, Writable)] support

2 releases

0.7.3 Nov 6, 2020
0.7.2 Nov 6, 2020

#338 in Encoding

Used in 2 crates (via persia-speedy)


1.5K SLoC

Build Status

A fast binary serialization framework


The goal of this crate is to provide fast, simple and easy binary serialization.


See serde-bench for benchmarks.


use std::borrow::Cow;
use speedy::{Readable, Writable, Endianness};

#[derive(PartialEq, Debug, Readable, Writable)]
enum Enum {

#[derive(PartialEq, Debug, Readable, Writable)]
struct Struct< 'a > {
    number: u64,
    string: String,
    vector: Vec< u8 >,
    cow: Cow< 'a, [i64] >,
    float: f32,
    enumeration: Enum

fn main() {
    let original = Struct {
        number: 0x12345678ABCDEF00,
        string: "A totally pointless string".to_owned(),
        vector: vec![ 1, 2, 3 ],
        cow: Cow::Borrowed( &[ 4, 5, 6 ] ),
        float: 3.1415,
        enumeration: Enum::C

    let endian = Endianness::LittleEndian;
    let bytes = original.write_to_vec_with_ctx( endian ).unwrap();
    let deserialized: Struct =
        Struct::read_from_buffer_with_ctx( endian, &bytes ).unwrap();

    assert_eq!( original, deserialized );

Supported types

Out-of-box the following types are supported:

Type Serialized as
u8 as-is
u16 as-is
u32 as-is
u64 as-is
usize u64
i8 as-is
i16 as-is
i32 as-is
i64 as-is
f32 as-is
f64 as-is
bool u8, either 0 or 1
String {length: u32, bytes: [u8]}
Cow<'a, str> {length: u32, bytes: [u8]}
Vec<T> {length: u32, values: [T]}
Cow<'a, [T]> {length: u32, values: [T]}
Range<T> (T, T)
Option<T> (1_u8, T) or 0_u8
() nothing
(T) as-is
(T, T) as-is
(T, .., T) as-is
enums {tag: u32, variant: T}

These are stable and will not change in the future.


#[speedy(length = ...)]

Can be used on a Vec<T> or on a Cow<'a, [T]> to specify the field's length. Can refer to any of the previous fields.

For example:

use speedy::{Readable, Writable};

#[derive(Readable, Writable)]
struct Struct {
    byte_count: u8,
    #[speedy(length = byte_count / 4)]
    data: Vec< u32 >

Before serializing you need to make sure that whatever is set as length is equal to the .len() of the field; if it's not then you will get an error when trying to serialize it.

Setting this attribute changes the serialization format as follows:

Type Serialized as
Vec<T> [T]
Cow<'a, [T]> [T]


Licensed under either of

at your option.


Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.


~21K SLoC