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 Protocol Buffers.

• 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.

NAME
	colf — compile Colfer schemas

SYNOPSIS
	colf [ options ] language [ file ... ]

DESCRIPTION
	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.

OPTIONS
  -b directory
    	Use a specific destination base directory. (default ".")
  -f	Normalizes the format of all input schemas on the fly.
  -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.

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

EXAMPLES
	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

BUGS
	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).

SEE ALSO
	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.

<plugin>
	<groupId>net.quies.colfer</groupId>
	<artifactId>colfer-maven-plugin</artifactId>
	<version>1.11.2</version>
	<configuration>
		<packagePrefix>com/example</packagePrefix>
	</configuration>
</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.

• † 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.