pinch: An alternative implementation of Thrift for Haskell.

pinch aims to provide an alternative implementation of Apache Thrift for Haskell. The pinch library itself acts only as a serialization library. Types specify their Thrift encoding by defining instances of the Pinchable typeclass, which may be done by hand or automatically with the use of Generics.

Haddock documentation for this package is avilable on Hackage and here.

Overview

Types which can be encoded into Thrift payloads implement the Pinchable typeclass.

Given the Thrift struct,

struct Person {
    1: required string name
    2: optional i64 dateOfBirth
}

You can write a Pinchable instance like so,

data Person = Person { name :: Text, dateOfBirth :: Maybe Int64 }
    deriving (Eq)

instance Pinchable Person where
    type Tag Person = TStruct
    -- The Tag tells the system that this represents a struct.

    pinch (Person name dateOfBirth) =
        struct [1 .= name, 2 ?= dateOfBirth]

    unpinch value =
        Person <$> value .:  1
               <*> value .:? 2

Better yet, you can drive an instance automatically.

{-# LANGUAGE DeriveGeneric, DataKinds #-}
import GHC.Generics (Generic)

data Person = Person
    { name        :: Field 1 Text
    , dateOfBirth :: Field 2 (Maybe Int64)
    } deriving (Eq, Generic)

instance Pinchable Person

Objects can be serialized and deserialized using the encode and decode methods. These methods accept a Protocol as an argument.

decode binaryProtocol (encode binaryProtocol person) == person

For more information, check the documentation and the examples.

Caveats

• Only the Thrift Binary Protocol is supported right now. (Pull requests welcome.)
• There is no code generation or template haskell support yet so types from the Thrift file will have to be translated by hand.