November 13, 2019

Package: Serialization

Minimum usable: configurator

There are many great Haskell libraries. But usually it will take equally great amount of effort for people to get familiar with them.
Worstly, it seems like some examples were designed to bring more obstracle deliberately. Package section follows the minimum usable principle. Examples of this section is clear enough for reminding myself in future. Hopefully, it will also offer some help to others.

online resouces:

store
cereal

Notes

Both packages can be used the same ways

GHC extension

{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE DefaultSignatures #-}
Import corresponding libraries:

sore package
```
import Data.Sort
```
cereal package
```
import Data.Serialize
```

Rely on GHC.Generics

     import GHC.Generics
     ...
     data DemoMap = DemoMap    
       { toMapList :: [([String], [Float])]    
       } deriving (Generic, Show)

Declare as Instance

store package

    instance Store DemoMap

cereal package

    instance Serialization DemoMap

Write to / Read from file by Data.ByteString

store pakcage

     import qualified Data.ByteString as BL
     ...
     serializeDemoMap:: FilePath -> StandardMap -> IO ()
     serializeDemoMap filePath sdmap = BL.writeFile filePath (encode sdmap)
                                          
     deserializeDemoMap :: FilePath -> IO (Either PeekException StandardMap)
     deserializeDemoMap filePath = do          
         bs <- BL.readFile filePath              
         return $ decode bs

cereal package

     import qualified Data.ByteString.Lazy as BL
     ...
     serializeDemoMap :: FilePath -> StandardMap -> IO ()
     serializeDemoMap filePath sdmap = BL.writeFile filePath (encodeLazy sdmap)

     deserializeDemoMap :: FilePath -> IO (Either String StandardMap)
     deserializeDemoMap filePath = do          
       bs <- BL.readFile filePath              
       return $ decodeLazy bs

The file produced by store is about 1/3 bigger than file produced by cereal.
store handles parametric data type more smoothly.
Performance test: TODO