Safe Haskell | None |
---|---|
Language | Haskell2010 |
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
- data HeaderParser a
- = FailH !ByteString String
- | PartialH (ByteString -> HeaderParser a)
- | DoneH !Header a
- decodeHeader :: HeaderParser ByteString
- decodeHeaderWith :: DecodeOptions -> HeaderParser ByteString
- data Parser a
- data HasHeader
- decode :: FromRecord a => HasHeader -> Parser a
- decodeWith :: FromRecord a => DecodeOptions -> HasHeader -> Parser a
- decodeByName :: FromNamedRecord a => HeaderParser (Parser a)
- decodeByNameWith :: FromNamedRecord a => DecodeOptions -> HeaderParser (Parser a)
- encode :: ToRecord a => Builder a -> ByteString
- encodeWith :: ToRecord a => EncodeOptions -> Builder a -> ByteString
- encodeRecord :: ToRecord a => a -> Builder a
- data Builder a
- encodeByName :: ToNamedRecord a => Header -> NamedBuilder a -> ByteString
- encodeDefaultOrderedByName :: (DefaultOrdered a, ToNamedRecord a) => NamedBuilder a -> ByteString
- encodeByNameWith :: ToNamedRecord a => EncodeOptions -> Header -> NamedBuilder a -> ByteString
- encodeDefaultOrderedByNameWith :: forall a. (DefaultOrdered a, ToNamedRecord a) => EncodeOptions -> NamedBuilder a -> ByteString
- encodeNamedRecord :: ToNamedRecord a => a -> NamedBuilder a
- data NamedBuilder a
Decoding
data HeaderParser a #
An incremental parser that when fed data eventually returns a
parsed Header
, or an error.
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 |
DoneH !Header a | The parse succeeded and produced the given |
Functor HeaderParser # | |
Show a => Show (HeaderParser a) # | |
decodeHeader :: HeaderParser ByteString #
Parse a CSV header in an incremental fashion. When done, the
HeaderParser
returns any unconsumed input in the second field of
the DoneH
constructor.
decodeHeaderWith :: DecodeOptions -> HeaderParser ByteString #
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.
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.
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 |
Done [Either String a] | The parser parsed and converted some records. Any records
that failed type conversion are returned as |
Index-based record conversion
See documentation on index-based conversion in Data.Csv for more information.
Is the CSV data preceded by a header?
:: FromRecord a | |
=> HasHeader | Data contains header that should be skipped |
-> Parser a |
Efficiently deserialize CSV in an incremental fashion. Equivalent
to
.decodeWith
defaultDecodeOptions
:: FromRecord a | |
=> DecodeOptions | Decoding options |
-> HasHeader | Data contains header that should be skipped |
-> Parser a |
Like decode
, but lets you customize how the CSV data is parsed.
Name-based record conversion
See documentation on name-based conversion in Data.Csv for more information.
decodeByName :: FromNamedRecord a => HeaderParser (Parser a) #
Efficiently deserialize CSV in an incremental fashion. The data
is assumed to be preceeded by a header. Returns a HeaderParser
that when done produces a Parser
for parsing the actual records.
Equivalent to
.decodeByNameWith
defaultDecodeOptions
:: FromNamedRecord a | |
=> DecodeOptions | Decoding options |
-> HeaderParser (Parser a) |
Like decodeByName
, but lets you customize how the CSV data is
parsed.
Encoding
Index-based record conversion
See documentation on index-based conversion in Data.Csv for more information.
encode :: ToRecord a => Builder a -> ByteString #
Efficiently serialize records in an incremental
fashion. Equivalent to
.encodeWith
defaultEncodeOptions
encodeWith :: ToRecord a => EncodeOptions -> Builder a -> ByteString #
Like encode
, but lets you customize how the CSV data is
encoded.
encodeRecord :: ToRecord a => a -> Builder a #
Encode a single record.
Name-based record conversion
See documentation on name-based conversion in Data.Csv for more information.
encodeByName :: ToNamedRecord a => Header -> NamedBuilder a -> ByteString #
Efficiently serialize named records in an incremental fashion,
including the leading header. Equivalent to
. The header is written before any records
and dictates the field order.encodeWith
defaultEncodeOptions
encodeDefaultOrderedByName :: (DefaultOrdered a, ToNamedRecord a) => NamedBuilder a -> ByteString #
Like encodeByName
, but header and field order is dictated by
the headerOrder
method.
encodeByNameWith :: ToNamedRecord a => EncodeOptions -> Header -> NamedBuilder a -> ByteString #
Like encodeByName
, but lets you customize how the CSV data is
encoded.
encodeDefaultOrderedByNameWith :: forall a. (DefaultOrdered a, ToNamedRecord a) => EncodeOptions -> NamedBuilder a -> ByteString #
Like encodeDefaultOrderedByName
, but lets you customize how the
CSV data is encoded.
encodeNamedRecord :: ToNamedRecord a => a -> NamedBuilder a #
Encode a single named record.
data NamedBuilder a #
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.
Monoid (NamedBuilder a) # | |