Safe Haskell	None

Data.CSV.Conduit

Contents

Key Operations
Convenience Functions
Important Types
Re-exported For Convenience

Synopsis

Key Operations

class CSV s r whereSource

Represents types r that are CSV-like and can be converted to/from an underlying stream of type s.

Example #1: Basics Using Convenience API

import Data.Conduit
import Data.Conduit.Binary
import Data.Conduit.List as CL
import Data.CSV.Conduit

myProcessor :: Conduit (Row Text) m (Row Text)
myProcessor = CL.map reverse

test = runResourceT $
  transformCSV defCSVSettings
               (sourceFile "input.csv")
               myProcessor
               (sinkFile "output.csv")

Example #2: Basics Using Conduit API

import Data.Conduit
import Data.Conduit.Binary
import Data.CSV.Conduit

myProcessor :: Conduit (MapRow Text) m (MapRow Text)
myProcessor = undefined

test = runResourceT $
  sourceFile "test/BigFile.csv" $=
  intoCSV defCSVSettings $=
  myProcessor $=
  (writeHeaders defCSVSettings >> fromCSV defCSVSettings) $$
  sinkFile "test/BigFileOut.csv"

Methods

rowToStr :: CSVSettings -> r -> sSource

Convert a CSV row into strict ByteString equivalent.

intoCSV :: MonadThrow m => CSVSettings -> Conduit s m rSource

Turn a stream of s into a stream of CSV row type. An example would be parsing a ByteString stream as rows of MapRow Text.

fromCSV :: Monad m => CSVSettings -> Conduit r m sSource

Turn a stream of CSV row type back into a stream of s. An example would be rendering a stream of Row ByteString rows as Text.

Instances

(CSV s (Row s'), Ord s', IsString s) => CSV s (MapRow s')	Generic `MapRow` instance; any stream type with a `Row` instance automatically gets a `MapRow` instance.
CSV ByteString (Row String)	`Row` instance using `String` based on `ByteString` stream. Please note this uses the ByteString operations underneath and has lots of unnecessary overhead. Included for convenience.
CSV ByteString (Row ByteString)	`Row` instance using `ByteString`
CSV ByteString (Row Text)	`Row` instance using `Text` based on `ByteString` stream
CSV Text (Row Text)	`Row` instance using `Text`

writeHeaders :: (Monad m, CSV s (Row r), IsString s) => CSVSettings -> Conduit (MapRow r) m sSource

Write headers AND the row into the output stream, once. Just chain this using the Monad instance in your pipeline:

 ... =$= writeHeaders settings >> fromCSV settings $$ sinkFile "..."

Convenience Functions

readCSVFile Source

Arguments

:: CSV ByteString a
=> CSVSettings	Settings to use in deciphering stream
-> FilePath	Input file
-> IO [a]

Read the entire contents of a CSV file into memory.

writeCSVFile Source

Arguments

:: CSV ByteString a
=> CSVSettings	CSV Settings
-> FilePath	Target file
-> IOMode	Write vs. append mode
-> [a]	List of rows
-> IO ()

Write CSV data into file.

transformCSV Source

Arguments

:: (MonadThrow m, CSV s a, CSV s' b)
=> CSVSettings	Settings to be used for both input and output
-> Source m s	A raw stream data source. Ex: 'sourceFile inFile'
-> Conduit a m b	A transforming conduit
-> Sink s' m ()	A raw stream data sink. Ex: 'sinkFile outFile'
-> m ()

General purpose CSV transformer. Apply a list-like processing function from List to the rows of a CSV stream. You need to provide a stream data source, a transformer and a stream data sink.

An easy way to run this function would be runResourceT after feeding it all the arguments.

Example - map a function over the rows of a CSV file:

 transformCSV set (sourceFile inFile) (C.map f) (sinkFile outFile)

mapCSVFile Source

Arguments

:: (MonadResource m, MonadThrow m, CSV ByteString a, CSV ByteString b)
=> CSVSettings	Settings to use both for both input and output
-> (a -> [b])	A mapping function
-> FilePath	Input file
-> FilePath	Output file
-> m ()

Map over the rows of a CSV file. Provided for convenience for historical reasons.

An easy way to run this function would be runResourceT after feeding it all the arguments.

Important Types

data CSVSettings Source

Settings for a CSV file. This library is intended to be flexible and offer a way to process the majority of text data files out there.

Constructors

CSVSettings
Fields csvSep :: !Char Separator character to be used in between fields csvQuoteChar :: !(Maybe Char) Quote character that may sometimes be present around fields. If `Nothing` is given, the library will never expect quotation even if it is present.

Instances

Eq CSVSettings
Read CSVSettings
Show CSVSettings
Default CSVSettings

defCSVSettings :: CSVSettings Source

Default settings for a CSV file.

 csvSep = ','
 csvQuoteChar = Just '"'

type MapRow a = Map a aSource

A MapRow is a dictionary based on Map

type Row a = [a]Source

A Row is just a list of fields

Re-exported For Convenience

runResourceT :: MonadBaseControl IO m => ResourceT m a -> m a