Programming language: Go
Tags: Serialization    
Latest version: v1.7.2

colfer alternatives and similar packages

Based on the "Serialization" category

Do you think we are missing an alternative of colfer or a related project?

Add another 'Serialization' Package


Colfer Build Status

Colfer is a binary serialization format optimized for speed and size.

The project's compiler colf(1) generates source code from schema definitions to marshal and unmarshall data structures.

This is free and unencumbered software released into the public domain. The format is inspired by Proto*col* Buf*fer*s.

Language Support

  • C, ISO/IEC 9899:2011 compliant a.k.a. C11, C++ compatible
  • Go, a.k.a. golang
  • Java, Android compatible
  • JavaScript, a.k.a. ECMAScript, NodeJS compatible


  • Simple and straightforward in use
  • No dependencies other than the core library
  • Both faster and smaller than the competition
  • Robust against malicious input
  • Maximum of 127 fields per data structure
  • No support for enumerations
  • Framed; suitable for concatenation/streaming


  • Rust and Python support
  • Protocol revision


Download a prebuilt compiler or run go get -u github.com/pascaldekloe/colfer/cmd/colf to make one yourself. Without arguments the command prints its manual.

    colf — compile Colfer schemas

    colf [ options ] language [ file ... ]

    Generates source code for a language. The options are: C, Go,
    Java and JavaScript.
    The file operands specify schema input. Directories are scanned
    for files with the colf extension. When no files are given, then
    the current working directory is used.
    A package definition may be spread over several schema files.
    The directory hierarchy of the input is not relevant for the
    generated code.

  -b directory
        Use a specific destination base directory. (default ".")
  -c file
        Insert code snippet from file. Java only.
  -f    Normalizes the format of all input schemas on the fly.
  -i interfaces
        Makes all generated classes implement the interfaces. Use commas
        to list and slash as a package separator. Java only.
  -l expression
        Sets the default upper limit for the number of elements in a
        list. The expression is applied to the target language under
        the name ColferListMax. (default "64 * 1024")
  -p prefix
        Adds a package prefix. Use slash as a separator when nesting.
  -s expression
        Sets the default upper limit for serial byte sizes. The
        expression is applied to the target language under the name
        ColferSizeMax. (default "16 * 1024 * 1024")
  -v    Enables verbose reporting to standard error.
  -x class
        Makes all generated classes extend a super class. Use slash as
        a package separator. Java only.

    The command exits 0 on succes, 1 on compilation failure and 2
    when invoked without arguments.

    Compile ./io.colf with compact limits as C:

        colf -b src -s 2048 -l 96 C io.colf

    Compile ./api/*.colf in package com.example as Java:

        colf -p com/example -x com/example/Parent Java api

    Report bugs at <https://github.com/pascaldekloe/colfer/issues>.

    Text validation is not part of the marshalling and unmarshalling
    process. C and Go just pass any malformed UTF-8 characters. Java
    and JavaScript replace unmappable content with the '?' character
    (ASCII 63).

    protoc(1), flatc(1)

It is recommended to commit the generated source code into the respective version control to preserve build consistency and minimise the need for compiler installations. Alternatively, you may use the Maven plugin.



Data structures are defined in .colf files. The format is quite self-explanatory.

// Package demo offers a demonstration.
// These comment lines will end up in the generated code.
package demo

// Course is the grounds where the game of golf is played.
type course struct {
    ID    uint64
    name  text
    holes []hole
    image binary
    tags  []text

type hole struct {
    // Lat is the latitude of the cup.
    lat float64
    // Lon is the longitude of the cup.
    lon float64
    // Par is the difficulty index.
    par uint8
    // Water marks the presence of water.
    water bool
    // Sand marks the presence of sand.
    sand bool

See what the generated code looks like in C, Go, Java or JavaScript.

The following table shows how Colfer data types are applied per language.

Colfer C Go Java JavaScript
bool char bool boolean Boolean
uint8 uint8_t uint8 byte † Number
uint16 uint16_t uint16 short † Number
uint32 uint32_t uint32 int † Number
uint64 uint64_t uint64 long † Number ‡
int32 int32_t int32 int Number
int64 int64_t int64 long Number ‡
float32 float float32 float Number
float64 double float64 double Number
timestamp timespec time.Time †† time.Instant Date + Number
text const char* + size_t string String †‡ String †‡
binary uint8_t* + size_t []byte byte[] Uint8Array
list * + size_t slice array Array
  • † signed representation of unsigned data, i.e. may overflow to negative.
  • ‡ range limited to [1 - 2⁵³, 2⁵³ - 1]
  • †† timezone not preserved
  • †‡ characters limited by UTF-16 [U+0000, U+10FFFF]

Lists may contain floating points, text, binaries or data structures.


Colfer is suited for untrusted data sources such as network I/O or bulk streams. Marshalling and unmarshalling comes with built-in size protection to ensure predictable memory consumption. The format prevents memory bombs by design.

The marshaller may not produce malformed output, regardless of the data input. In no event may the unmarshaller read outside the boundaries of a serial. Fuzz testing did not reveal any volnurabilities yet. Computing power is welcome.


Name changes do not affect the serialization format. Deprecated fields should be renamed to clearly discourage their use. For backwards compatibility new fields must be added to the end of colfer structs. Thus the number of fields can be seen as the schema version.


Colfer aims to be the fastest and the smallest format without compromising on reliability. See the benchmark wiki for a comparison. Suboptimal performance is treated like a bug.