Modulecassava-0.5.4.1Haskell2010

Data.Csv.Incremental

This module allows for incremental decoding and encoding of CSV data. This is useful if you e.g. want to interleave I/O with parsing or if you want finer grained control over how you deal with type conversion errors.

Decoding example:

main :: IO ()
main = withFile "salaries.csv" ReadMode $ \ csvFile -> do
    let loop !_ (Fail _ errMsg) = putStrLn errMsg >> exitFailure
        loop acc (Many rs k)    = loop (acc + sumSalaries rs) =<< feed k
        loop acc (Done rs)      = putStrLn $ "Total salaries: " ++
                                  show (sumSalaries rs + acc)

        feed k = do
            isEof <- hIsEOF csvFile
            if isEof
                then return $ k B.empty
                else k `fmap` B.hGetSome csvFile 4096
    loop 0 (decode NoHeader)
  where
    sumSalaries rs = sum [salary | Right (_ :: String, salary :: Int) <- rs]

Encoding example:

data Person = Person { name   :: !String, salary :: !Int }
    deriving Generic

instance FromNamedRecord Person
instance ToNamedRecord Person
instance DefaultOrdered Person

persons :: [Person]
persons = [Person "John" 50000, Person "Jane" 60000]

main :: IO ()
main = putStrLn $ encodeDefaultOrderedByName (go persons)
  where
    go (x:xs) = encodeNamedRecord x <> go xs

Contents

Decoding
Index-based record conversion
Name-based record conversion
Encoding
Index-based record conversion
Name-based record conversion

Synopsis

data HeaderParser
value decodeHeader
value decodeHeaderWith
data Parser
data HasHeader
value decode
value decodeWith
value decodeWithP
value decodeByName
value decodeByNameWith
value decodeByNameWithP
value encode
value encodeWith
value encodeRecord
newtype Builder
value encodeByName
value encodeDefaultOrderedByName
value encodeByNameWith
value encodeDefaultOrderedByNameWith
value encodeNamedRecord
newtype NamedBuilder

Packagecassava-0.5.4.1
Exports21
LanguageHaskell2010
LicenceBSD-3-Clause
SourceIncremental.hs

Decoding

datadata HeaderParser a

Source#

An incremental parser that when fed data eventually returns a parsed Header, or an error.

Constructors

FailH !ByteString String
The input data was malformed. The first field contains any unconsumed input and second field contains information about the parse error.
PartialH (ByteString -> HeaderParser a)
The parser needs more input data before it can produce a result. Use an empty string to indicate that no more input data is available. If fed an 'B.empty string', the continuation is guaranteed to return either FailH or DoneH.
DoneH !Header a
The parse succeeded and produced the given Header.

Instances2Functor, Show

Functor HeaderParserDefined in cassava-0.5.4.1 · Data.Csv.Incremental
Show a => Show (HeaderParser a)Defined in cassava-0.5.4.1 · Data.Csv.Incremental

valuedecodeHeader :: HeaderParser ByteString

Source#

Parse a CSV header in an incremental fashion. When done, the HeaderParser returns any unconsumed input in the second field of the DoneH constructor.

valuedecodeHeaderWith :: DecodeOptions -> HeaderParser ByteString

Source#

Like decodeHeader, but lets you customize how the CSV data is parsed.

Just like in the case of non-incremental decoding, there are two ways to convert CSV records to and from and user-defined data types: index-based conversion and name-based conversion.

datadata Parser a

Source#

An incremental parser that when fed data eventually produces some parsed records, converted to the desired type, or an error in case of malformed input data.

Constructors

Fail !ByteString String
The input data was malformed. The first field contains any unconsumed input and second field contains information about the parse error.
Many [Either String a] (ByteString -> Parser a)
The parser parsed and converted zero or more records. Any records that failed type conversion are returned as Left errMsg and the rest as Right val. Feed a ByteString to the continuation to continue parsing. Use an empty string to indicate that no more input data is available. If fed an empty string, the continuation is guaranteed to return either Fail or Done.
Done [Either String a]
The parser parsed and converted some records. Any records that failed type conversion are returned as Left errMsg and the rest as Right val.

Instances2Functor, Show

Functor ParserDefined in cassava-0.5.4.1 · Data.Csv.Incremental
Show a => Show (Parser a)Defined in cassava-0.5.4.1 · Data.Csv.Incremental

Index-based record conversion

See documentation on index-based conversion in Data.Csv for more information.

datadata HasHeader

Source#

Is the CSV data preceded by a header?

Constructors

HasHeader
The CSV data is preceded by a header
NoHeader
The CSV data is not preceded by a header

valuedecode

:: FromRecord a
=> HasHeader
Data contains header that should be skipped
-> Parser a

Source#

Efficiently deserialize CSV in an incremental fashion. Equivalent to decodeWith defaultDecodeOptions.

valuedecodeWith

:: FromRecord a
=> DecodeOptions
Decoding options
-> HasHeader
Data contains header that should be skipped
-> Parser a

Source#

Like decode, but lets you customize how the CSV data is parsed.

valuedecodeWithP

:: (Record -> Parser a)
-> DecodeOptions
Decoding options
-> HasHeader
Data contains header that should be skipped
-> Parser a

Source#

Like decodeWith, but lets you pass an explicit parser value instead of using a typeclass

Name-based record conversion

See documentation on name-based conversion in Data.Csv for more information.

valuedecodeByName :: FromNamedRecord a => HeaderParser (Parser a)

Source#

Efficiently deserialize CSV in an incremental fashion. The data is assumed to be preceded by a header. Returns a HeaderParser that when done produces a Parser for parsing the actual records. Equivalent to decodeByNameWith defaultDecodeOptions.

valuedecodeByNameWith

:: FromNamedRecord a
=> DecodeOptions
Decoding options
-> HeaderParser (Parser a)

Source#

Like decodeByName, but lets you customize how the CSV data is parsed.

valuedecodeByNameWithP

:: (NamedRecord -> Parser a)
-> DecodeOptions
Decoding options
-> HeaderParser (Parser a)

Source#

Like decodeByNameWith, but lets you pass an explicit parser value instead of using a typeclass

Encoding

Index-based record conversion

See documentation on index-based conversion in Data.Csv for more information.

valueencode :: ToRecord a => Builder a -> ByteString

Source#

Efficiently serialize records in an incremental fashion. Equivalent to encodeWith defaultEncodeOptions.

valueencodeWith :: ToRecord a => EncodeOptions -> Builder a -> ByteString

Source#

Like encode, but lets you customize how the CSV data is encoded.

valueencodeRecord :: ToRecord a => a -> Builder a

Source#

Encode a single record.

newtypenewtype Builder a

Source#

A builder for building the CSV data incrementally. Just like the ByteString builder, this builder should be used in a right-associative, foldr style. Using <> to compose builders in a left-associative, foldl' style makes the building not be incremental.

Instances2Semigroup, Monoid

Semigroup (Builder a)Defined in cassava-0.5.4.1 · Data.Csv.Incremental
Monoid (Builder a)Defined in cassava-0.5.4.1 · Data.Csv.Incremental

Name-based record conversion

See documentation on name-based conversion in Data.Csv for more information.

valueencodeByName :: ToNamedRecord a => Header -> NamedBuilder a -> ByteString

Source#

Efficiently serialize named records in an incremental fashion, including the leading header. Equivalent to encodeWith defaultEncodeOptions. The header is written before any records and dictates the field order.

valueencodeDefaultOrderedByName