scodec

Scala combinator library for working with binary data.

Design Constraints

This library focuses on contract-first and pure functional encoding and decoding of binary data. The following design constraints are considered:

Binary structure should mirror protocol definitions and be self-evident under casual reading
Mapping binary structures to types should be statically verified
Encoding and decoding should be purely functional
Failures in encoding and decoding should provide descriptive errors
Compiler plugin should not be used

As a result, the library is implemented as a combinator based DSL. Performance is considered but yields to the above design constraints.

Acknowledgements

The library uses Scalaz and Shapeless and is heavily influenced by scala.util.parsing.combinator.

Introduction

The primary abstraction is a Codec[A], which supports encoding a value of type A to a BitVector and decoding a BitVector to a value of type A.

The codecs package provides a number of predefined codecs and combinators.

    import scodec._
    import scodec.bits._
    import codecs._
    import scalaz.\/

    // Create a codec for an 8-bit unsigned int followed by an 8-bit unsigned int followed by a 16-bit unsigned int
    val firstCodec = (uint8 ~ uint8 ~ uint16)

    // Decode a bit vector using that codec
    val result: String \/ (Int ~ Int ~ Int) = Codec.decode(firstCodec, BitVector(0x10, 0x2a, 0x03, 0xff))

    // Sum the result
    val add3 = (_: Int) + (_: Int) + (_: Int)
    val sum: String \/ Int = result map add3

Automatic case class binding is supported via Shapeless HLists:

    import shapeless._

    case class Point(x: Int, y: Int, z: Int)

    val pointCodec = (int8 :: int8 :: int8).as[Point]

    val encoded: String \/ BitVector = pointCodec.encode(Point(-5, 10, 1))
    // \/-(BitVector(24 bits, 0xfb0a01))

    val decoded: String \/ Point = Codec.decode(pointCodec, BitVector(0xfb, 0x0a, 0x01))
    // \/-(Point(-5,10,1))

Codecs can also be implicitly resolved, resulting in usage like:

    // Assuming Codec[Point] is in implicit scope

    val encoded = Codec.encode(Point(-5, 10, 1))
    // \/-(BitVector(24 bits, 0xfb0a01))

    val decoded = Codec.decode[Point](BitVector(0xfb, 0x0a, 0x01))
    // \/-(Point(-5,10,1))

New codecs can be created by either implementing the Codec trait or by passing an encoder function and decoder function to the Codec apply method. Typically, new codecs are created by applying one or more combinators to existing codecs.

See ScalaDoc for more information. Especially:

Examples

There are various examples in the test directory, including codecs for:

Getting Binaries

This library works with Scala 2.10 and 2.11.

ScalaDoc for the latest version is available here: http://scodec.github.io/scodec/latest/api.

Releases

Version 1.2.0

Compatible with Scalaz 7.1.* and Shapeless 2.0.0
ScalaDoc

Version 1.1.0

Compatible with Scalaz 7.0.* and Shapeless 2.0.0
ScalaDoc

Version 1.0.0

Compatible with Scalaz 7.0.* and Shapeless 1.2.4
ScalaDoc

For SBT users:

libraryDependencies += "org.typelevel" %% "scodec-core" % "1.2.0"

For Maven users:

<dependencies>
  <dependency>
    <groupId>org.typelevel</groupId>
    <artifactId>scodec-core_2.11</artifactId>
    <version>1.2.0</version>
  </dependency>
</dependencies>

Snapshots

Snapshot builds of the master branch are available on Sonatype's OSS hosting at https://oss.sonatype.org/content/repositories/snapshots/.

Compatible with Scalaz 7.1.* and Shapeless 2.0