Skip to content
Functional, declarative binary codec library for Rust
Branch: master
Clone or download
Type Name Latest commit message Commit time
Failed to load latest commit information.


Build Status MIT licensed

This Rust library provides combinators for purely functional, declarative encoding and decoding of binary data. Its design is largely derived from that of the scodec library for Scala.


Add the following dependencies to your Cargo.toml:

pl-hlist = "1.0"
rcodec = "1.0"

Then, in your crate:

use pl_hlist::*;
use rcodec::byte_vector;
use rcodec::codec::*;


The codec module provides a number of predefined codecs. In the following example, we use the uint32 codec to encode a u32 value to a ByteVector representation, and then decode the ByteVector back to its u32 representation:

let codec = uint32;
let v0 = 258u32;
let bv = codec.encode(v0).unwrap();
assert_eq(bv, byte_vector!(0x00, 0x00, 0x01, 0x02));
let v1 = codec.decode(bv).unwrap().value;
assert_eq(v0, v1);

Automatic binding to structs when encoding/decoding is supported via the pl-hlist crate:

#[derive(Debug, PartialEq, Eq, Clone, HListSupport)]
struct TestStruct {
    foo: u8,
    bar: u16

let codec = struct_codec!(TestStruct from {uint8} :: {uint16});
let s0 = TestStruct { foo: 7u8, bar: 3u16 };
let bv = codec.encode(&s0).unwrap();
assert_eq(bv, byte_vector!(7, 0, 3));
let s1 = codec.decode(&bv).unwrap().value;
assert_eq(s0, s1);

Here's an example of a more complex codec for a fictitious binary packet format, which uses a number of the built-in combinators:

#[derive(Debug, PartialEq, Eq, Clone, HListSupport)]
struct PacketHeader {
    version: u8,
    port: u16,
    checksum: u16,
    data_len: u16

#[derive(Debug, PartialEq, Eq, Clone, HListSupport)]
struct Packet {
    header: PacketHeader,
    flags: u64,
    data: Vec<u8>

let magic = byte_vector!(0xCA, 0xFE, 0xCA, 0xFE);

let header_codec = struct_codec!(
    PacketHeader from
    { "version"      => uint8  } ::
    { "port"         => uint16 } ::
    { "checksum"     => uint16 } ::
    { "data_len"     => uint16 }

let packet_codec = struct_codec!(
    Packet from
    { "magic"           => constant(&magic) } >>
    { "padding"         => ignore(4)        } >>
    { "header"          => header_codec     } >>= |hdr| {
            { "flags"    => uint64                                       } ::
            { "data"     => eager(bytes((hdr.data_len - 8u16) as usize)) })

More examples of specific codecs can be found in the tests for src/ as well as in tests/


rcodec is distributed under an MIT license. See LICENSE for more details.

You can’t perform that action at this time.