Codec.Compression.Lzlib

Mid-level FFI bindings in the IO monad to lzlib.

See also Codec.Compression.Lzlib.ST for the ST monad version.

Compression functions

data LzEncoder

lzlib compressor handle.

data CompressParams

Parameters for lzip compressor

If compressDictionarySize is 65535 and compressMatchLenLimit is 16, the "fast variant" of LZMA is chosen.

Constructors

CompressParams

Fields

• compressDictionarySize :: !Int

  Valid values range from 4 KiB to 512 MiB; will be rounded upwards by adding up to (compressDictionarySize / 8) to match size supported by lzip format.

• compressMatchLenLimit :: !Int

  Valid values range from 5 to 273 bytes.

• compressMemberSize :: !Word64

  Valid values range from 100 kB to 2 PiB.

compressParamPreset :: Int -> CompressParams

Construct CompressParams based on the standard preset levels used by the lzip command-line interface.

The table below shows the parameters as a function of the level input argument:

level	compressDictionarySize	compressMatchLenLimit
≤0	65535 bytes	16 bytes
1	1 MiB	5 bytes
2	1.5 MiB	6 bytes
3	2 MiB	8 bytes
4	3 MiB	12 bytes
5	4 MiB	20 bytes
6	8 MiB	36 bytes
7	16 MiB	68 bytes
8	24 MiB	132 bytes
≥9	32 MiB	273 bytes

compressMemberSize is set to its maximum allowed value (i.e. 2 PiB) for all compression levels.

NOTE: The "0" preset parameters will cause the encoder to use the "fast variant" of the LZMA algorithm.

lzCompressOpen :: CompressParams -> IO (Either LzErrno LzEncoder)

Construct new LzEncoder.

If a LzEncoder was constructed succesfully it will be in the LzOk state (as reported by lzCompressErrno).

NOTE: lzCompressClose will be invoked automatically when LzEncoder is garbage collected.

lzCompressClose :: LzEncoder -> IO ()

Promptly finalize a LzEncoder.

It is not necessary to invoke lzCompressClose explicitly as it will be invoked implicitly when a LzEncoder is garbage collected.

See also lzCompressOpen.

lzCompressRead :: LzEncoder -> Int -> IO ByteString

Retrieve up to n bytes of the compressed stream from the encoder.

Returns the empty ByteString when the output buffer has been drained.

lzCompressWrite :: LzEncoder -> ByteString -> IO Int

Push uncompressed data into the encoder. The return value is the number of bytes actually consumed.

lzCompressSyncFlush :: LzEncoder -> IO LzErrno

Force the encoder to output the compressed stream for all the uncompressed input data.

After this operation, the output buffer has to be drained via repeated invocations of lzCompressRead.

lzCompressFinish :: LzEncoder -> IO LzErrno

Finalize current member.

After this operation, the output buffer has to be drained via repeated invocations of lzCompressRead.

See also lzCompressFinished and lzCompressMemberFinished.

lzCompressFinished :: LzEncoder -> IO Bool

Returns True if the output buffer has been drained completely (which implies lzCompressMemberFinished).

lzCompressMemberFinished :: LzEncoder -> IO Bool

Returns True if the output buffer has been drained completely and lzCompressRestartMember can be invoked.

lzCompressRestartMember :: LzEncoder -> Word64 -> IO LzErrno

Start a new member in a multimember compression stream.

Must only be called when lzCompressMemberFinished is True.

Decompression functions

data LzDecoder

lzlib decompressor handle.

lzDecompressOpen :: IO (Either LzErrno LzDecoder)

Construct new LzDecoder.

If a LzDecoder was constructed succesfully it will be in the LzOk state (as reported by lzDecompressErrno).

NOTE: lzDecompressClose will be invoked automatically when LzDecoder is garbage collected.

lzDecompressClose :: LzDecoder -> IO ()

Promptly finalize a LzDecoder.

It is not necessary to invoke lzDecompressClose explicitly as it will be invoked implicitly when a LzDecoder is garbage collected.

See also lzDecompressOpen.

lzDecompressRead :: LzDecoder -> Int -> IO ByteString

Retrieve up to n bytes of the decompressed stream from the decoder.

Returns the empty ByteString when the output buffer has been drained.

lzDecompressWrite :: LzDecoder -> ByteString -> IO Int

Push compressed data into the decoder. The return value is the number of bytes actually consumed.

lzDecompressSyncToMember :: LzDecoder -> IO LzErrno

Instruct decoder to discard data of current member and skip till next member.

This is a no-op if the decoder is already at the start of a member.

lzDecompressFinish :: LzDecoder -> IO LzErrno

Finalize current member.

After this operation, the output buffer has to be drained via repeated invocations of lzDecompressRead.

See also lzDecompressFinished and lzDecompressMemberFinished.

lzDecompressFinished :: LzDecoder -> IO Bool

Returns True if the output buffer has been drained completely (which implies lzDecompressMemberFinished).

lzDecompressMemberFinished :: LzDecoder -> IO Bool

Returns True if the output buffer has been drained completely and lzDecompressRestartMember can be invoked.

lzDecompressReset :: LzDecoder -> IO LzErrno

Reset LzEncoder into the initial state (as if lzCompressOpen had just been invoked) and discard all data.

Error codes

data LzErrno

lzlib error codes

See lzlib manual for more details.

Constructors

LzOk

LzBadArgument

LzMemError

LzSequenceError

LzHeaderError

LzUnexpectedEof

LzDataError

LzLibraryError

LzUnknown

not defined by lzlib

Instances

Eq LzErrno

Defined in Codec.Compression.Lzlib.FFI

Methods

(==) :: LzErrno -> LzErrno -> Bool

(/=) :: LzErrno -> LzErrno -> Bool

Show LzErrno

Defined in Codec.Compression.Lzlib.FFI

Methods

showsPrec :: Int -> LzErrno -> ShowS

show :: LzErrno -> String

showList :: [LzErrno] -> ShowS

Exception LzErrno

Defined in Codec.Compression.Lzlib.FFI

Methods

toException :: LzErrno -> SomeException

fromException :: SomeException -> Maybe LzErrno

displayException :: LzErrno -> String