Copyright	(c) 2006-2015 Duncan Coutts
License	BSD-style
Maintainer	duncan@community.haskell.org
Safe Haskell	Trustworthy
Language	Haskell2010

Codec.Compression.Zlib.Internal

Contents

Pure interface
Monadic incremental interface
- Using incremental compression
- Using incremental decompression
The compression parameter types

Description

Pure and IO stream based interfaces to lower level zlib wrapper

Synopsis

compress :: Format -> CompressParams -> ByteString -> ByteString
decompress :: Format -> DecompressParams -> ByteString -> ByteString
data CompressStream m
- = CompressInputRequired {
  - compressSupplyInput :: ByteString -> m ( CompressStream m)
  }
- | CompressOutputAvailable {
  - compressOutput :: ! ByteString
  - compressNext :: m ( CompressStream m)
  }
- | CompressStreamEnd
compressST :: Format -> CompressParams -> CompressStream ( ST s)
compressIO :: Format -> CompressParams -> CompressStream IO
foldCompressStream :: Monad m => (( ByteString -> m a) -> m a) -> ( ByteString -> m a -> m a) -> m a -> CompressStream m -> m a
foldCompressStreamWithInput :: ( ByteString -> a -> a) -> a -> ( forall s. CompressStream ( ST s)) -> ByteString -> a
data DecompressStream m
- = DecompressInputRequired {
  - decompressSupplyInput :: ByteString -> m ( DecompressStream m)
  }
- | DecompressOutputAvailable {
  - decompressOutput :: ! ByteString
  - decompressNext :: m ( DecompressStream m)
  }
- | DecompressStreamEnd {
  - decompressUnconsumedInput :: ByteString
  }
- | DecompressStreamError {
  - decompressStreamError :: DecompressError
  }
data DecompressError
- = TruncatedInput
- | DictionaryRequired
- | DictionaryMismatch
- | DataFormatError String
decompressST :: Format -> DecompressParams -> DecompressStream ( ST s)
decompressIO :: Format -> DecompressParams -> DecompressStream IO
foldDecompressStream :: Monad m => (( ByteString -> m a) -> m a) -> ( ByteString -> m a -> m a) -> ( ByteString -> m a) -> ( DecompressError -> m a) -> DecompressStream m -> m a
foldDecompressStreamWithInput :: ( ByteString -> a -> a) -> ( ByteString -> a) -> ( DecompressError -> a) -> ( forall s. DecompressStream ( ST s)) -> ByteString -> a
data CompressParams = CompressParams {
- compressLevel :: ! CompressionLevel
- compressMethod :: ! Method
- compressWindowBits :: ! WindowBits
- compressMemoryLevel :: ! MemoryLevel
- compressStrategy :: ! CompressionStrategy
- compressBufferSize :: ! Int
- compressDictionary :: Maybe ByteString
}
defaultCompressParams :: CompressParams
data DecompressParams = DecompressParams {
- decompressWindowBits :: ! WindowBits
- decompressBufferSize :: ! Int
- decompressDictionary :: Maybe ByteString
- decompressAllMembers :: Bool
}
defaultDecompressParams :: DecompressParams
data Format
- = GZip
- | Zlib
- | Raw
- | GZipOrZlib
gzipFormat :: Format
zlibFormat :: Format
rawFormat :: Format
gzipOrZlibFormat :: Format
data CompressionLevel
- = DefaultCompression
- | NoCompression
- | BestSpeed
- | BestCompression
- | CompressionLevel Int
defaultCompression :: CompressionLevel
noCompression :: CompressionLevel
bestSpeed :: CompressionLevel
bestCompression :: CompressionLevel
compressionLevel :: Int -> CompressionLevel
data Method = Deflated
deflateMethod :: Method
data WindowBits
- = WindowBits Int
- | DefaultWindowBits
defaultWindowBits :: WindowBits
windowBits :: Int -> WindowBits
data MemoryLevel
- = DefaultMemoryLevel
- | MinMemoryLevel
- | MaxMemoryLevel
- | MemoryLevel Int
defaultMemoryLevel :: MemoryLevel
minMemoryLevel :: MemoryLevel
maxMemoryLevel :: MemoryLevel
memoryLevel :: Int -> MemoryLevel
data CompressionStrategy
- = DefaultStrategy
- | Filtered
- | HuffmanOnly
defaultStrategy :: CompressionStrategy
filteredStrategy :: CompressionStrategy
huffmanOnlyStrategy :: CompressionStrategy

Pure interface

compress :: Format -> CompressParams -> ByteString -> ByteString Source #

Compress a data stream provided as a lazy ByteString .

There are no expected error conditions. All input data streams are valid. It is possible for unexpected errors to occur, such as running out of memory, or finding the wrong version of the zlib C library, these are thrown as exceptions.

decompress :: Format -> DecompressParams -> ByteString -> ByteString Source #

Decompress a data stream provided as a lazy ByteString .

It will throw an exception if any error is encountered in the input data. If you need more control over error handling then use one the incremental versions, decompressST or decompressIO .

Monadic incremental interface

The pure compress and decompress functions are streaming in the sense that they can produce output without demanding all input, however they need the input data stream as a lazy ByteString . Having the input data stream as a lazy ByteString often requires using lazy I/O which is not appropriate in all circumstances.

For these cases an incremental interface is more appropriate. This interface allows both incremental input and output. Chunks of input data are supplied one by one (e.g. as they are obtained from an input source like a file or network source). Output is also produced chunk by chunk.

The incremental input and output is managed via the CompressStream and DecompressStream types. They represents the unfolding of the process of compressing and decompressing. They operates in either the ST or IO monads. They can be lifted into other incremental abstractions like pipes or conduits, or they can be used directly in the following style.

Using incremental compression

In a loop:

Inspect the status of the stream
When it is CompressInputRequired then you should call the action, passing a chunk of input (or empty when no more input is available) to get the next state of the stream and continue the loop.
When it is CompressOutputAvailable then do something with the given chunk of output, and call the action to get the next state of the stream and continue the loop.
When it is CompressStreamEnd then terminate the loop.

Note that you cannot stop as soon as you have no more input, you need to carry on until all the output has been collected, i.e. until you get to CompressStreamEnd .

Here is an example where we get input from one file handle and send the compressed output to another file handle.

go :: Handle -> Handle -> CompressStream IO -> IO ()
go inh outh (CompressInputRequired next) = do
   inchunk <- BS.hGet inh 4096
   go inh outh =<< next inchunk
go inh outh (CompressOutputAvailable outchunk next) =
   BS.hPut outh outchunk
   go inh outh =<< next
go _ _ CompressStreamEnd = return ()

The same can be achieved with foldCompressStream :

foldCompressStream
  (\next -> do inchunk <- BS.hGet inh 4096; next inchunk)
  (\outchunk next -> do BS.hPut outh outchunk; next)
  (return ())

data CompressStream m Source #

The unfolding of the compression process, where you provide a sequence of uncompressed data chunks as input and receive a sequence of compressed data chunks as output. The process is incremental, in that the demand for input and provision of output are interleaved.

Constructors

CompressInputRequired
Fields compressSupplyInput :: ByteString -> m ( CompressStream m)
CompressOutputAvailable
Fields compressOutput :: ! ByteString compressNext :: m ( CompressStream m)
CompressStreamEnd

compressST :: Format -> CompressParams -> CompressStream ( ST s) Source #

Incremental compression in the ST monad. Using ST makes it possible to write pure lazy functions while making use of incremental compression.

compressIO :: Format -> CompressParams -> CompressStream IO Source #

Incremental compression in the IO monad.

foldCompressStream :: Monad m => (( ByteString -> m a) -> m a) -> ( ByteString -> m a -> m a) -> m a -> CompressStream m -> m a Source #

A fold over the CompressStream in the given monad.

One way to look at this is that it runs the stream, using callback functions for the three stream events.

foldCompressStreamWithInput :: ( ByteString -> a -> a) -> a -> ( forall s. CompressStream ( ST s)) -> ByteString -> a Source #

A variant on foldCompressStream that is pure rather than operating in a monad and where the input is provided by a lazy ByteString . So we only have to deal with the output and end parts, making it just like a foldr on a list of output chunks.

For example:

toChunks = foldCompressStreamWithInput (:) []

Using incremental decompression

The use of DecompressStream is very similar to CompressStream but with a few differences:

There is the extra possibility of a DecompressStreamError
There can be extra trailing data after a compressed stream, and the DecompressStreamEnd includes that.

Otherwise the same loop style applies, and there are fold functions.

data DecompressStream m Source #

The unfolding of the decompression process, where you provide a sequence of compressed data chunks as input and receive a sequence of uncompressed data chunks as output. The process is incremental, in that the demand for input and provision of output are interleaved.

To indicate the end of the input supply an empty input chunk. Note that for gzipFormat with the default decompressAllMembers True you will have to do this, as the decompressor will look for any following members. With decompressAllMembers False the decompressor knows when the data ends and will produce DecompressStreamEnd without you having to supply an empty chunk to indicate the end of the input.

Constructors

DecompressInputRequired
Fields decompressSupplyInput :: ByteString -> m ( DecompressStream m)
DecompressOutputAvailable
Fields decompressOutput :: ! ByteString decompressNext :: m ( DecompressStream m)
DecompressStreamEnd	Includes any trailing unconsumed input data.
Fields decompressUnconsumedInput :: ByteString
DecompressStreamError	An error code
Fields decompressStreamError :: DecompressError

data DecompressError Source #

The possible error cases when decompressing a stream.

This can be show n to give a human readable error message.

Constructors

TruncatedInput	The compressed data stream ended prematurely. This may happen if the input data stream was truncated.
DictionaryRequired	It is possible to do zlib compression with a custom dictionary. This allows slightly higher compression ratios for short files. However such compressed streams require the same dictionary when decompressing. This error is for when we encounter a compressed stream that needs a dictionary, and it's not provided.
DictionaryMismatch	If the stream requires a dictionary and you provide one with the wrong `DictionaryHash` then you will get this error.
DataFormatError String	If the compressed data stream is corrupted in any way then you will get this error, for example if the input data just isn't a compressed zlib data stream. In particular if the data checksum turns out to be wrong then you will get all the decompressed data but this error at the end, instead of the normal successful `StreamEnd` .

Instances

Instances details

Eq DecompressError Source #
Instance details Defined in Codec.Compression.Zlib.Internal Methods (==) :: DecompressError -> DecompressError -> Bool Source # (/=) :: DecompressError -> DecompressError -> Bool Source #
Show DecompressError Source #
Instance details Defined in Codec.Compression.Zlib.Internal Methods showsPrec :: Int -> DecompressError -> ShowS Source # show :: DecompressError -> String Source # showList :: [ DecompressError ] -> ShowS Source #
Exception DecompressError Source #
Instance details Defined in Codec.Compression.Zlib.Internal Methods toException :: DecompressError -> SomeException Source # fromException :: SomeException -> Maybe DecompressError Source # displayException :: DecompressError -> String Source #

decompressST :: Format -> DecompressParams -> DecompressStream ( ST s) Source #

Incremental decompression in the ST monad. Using ST makes it possible to write pure lazy functions while making use of incremental decompression.

decompressIO :: Format -> DecompressParams -> DecompressStream IO Source #

Incremental decompression in the IO monad.

foldDecompressStream :: Monad m => (( ByteString -> m a) -> m a) -> ( ByteString -> m a -> m a) -> ( ByteString -> m a) -> ( DecompressError -> m a) -> DecompressStream m -> m a Source #

A fold over the DecompressStream in the given monad.

One way to look at this is that it runs the stream, using callback functions for the four stream events.

foldDecompressStreamWithInput :: ( ByteString -> a -> a) -> ( ByteString -> a) -> ( DecompressError -> a) -> ( forall s. DecompressStream ( ST s)) -> ByteString -> a Source #

A variant on foldCompressStream that is pure rather than operating in a monad and where the input is provided by a lazy ByteString . So we only have to deal with the output, end and error parts, making it like a foldr on a list of output chunks.

For example:

toChunks = foldDecompressStreamWithInput (:) [] throw

The compression parameter types

data CompressParams Source #

The full set of parameters for compression. The defaults are defaultCompressParams .

The compressBufferSize is the size of the first output buffer containing the compressed data. If you know an approximate upper bound on the size of the compressed data then setting this parameter can save memory. The default compression output buffer size is 16k . If your estimate is wrong it does not matter too much, the default buffer size will be used for the remaining chunks.

Constructors

CompressParams
Fields compressLevel :: ! CompressionLevel compressMethod :: ! Method compressWindowBits :: ! WindowBits compressMemoryLevel :: ! MemoryLevel compressStrategy :: ! CompressionStrategy compressBufferSize :: ! Int compressDictionary :: Maybe ByteString

Instances

Instances details

Show CompressParams Source #
Instance details Defined in Codec.Compression.Zlib.Internal Methods showsPrec :: Int -> CompressParams -> ShowS Source # show :: CompressParams -> String Source # showList :: [ CompressParams ] -> ShowS Source #

defaultCompressParams :: CompressParams Source #

The default set of parameters for compression. This is typically used with the compressWith function with specific parameters overridden.

data DecompressParams Source #

The full set of parameters for decompression. The defaults are defaultDecompressParams .

The decompressBufferSize is the size of the first output buffer, containing the uncompressed data. If you know an exact or approximate upper bound on the size of the decompressed data then setting this parameter can save memory. The default decompression output buffer size is 32k . If your estimate is wrong it does not matter too much, the default buffer size will be used for the remaining chunks.

One particular use case for setting the decompressBufferSize is if you know the exact size of the decompressed data and want to produce a strict ByteString . The compression and decompression functions use lazy ByteString s but if you set the decompressBufferSize correctly then you can generate a lazy ByteString with exactly one chunk, which can be converted to a strict ByteString in O(1) time using concat . toChunks .

Constructors

DecompressParams
Fields decompressWindowBits :: ! WindowBits decompressBufferSize :: ! Int decompressDictionary :: Maybe ByteString decompressAllMembers :: Bool

Instances

Instances details

Show DecompressParams Source #
Instance details Defined in Codec.Compression.Zlib.Internal Methods showsPrec :: Int -> DecompressParams -> ShowS Source # show :: DecompressParams -> String Source # showList :: [ DecompressParams ] -> ShowS Source #

defaultDecompressParams :: DecompressParams Source #

The default set of parameters for decompression. This is typically used with the compressWith function with specific parameters overridden.

data Format Source #

The format used for compression or decompression. There are three variations.

Constructors

GZip	Deprecated: Use gzipFormat. Format constructors will be hidden in version 0.7
Zlib	Deprecated: Use zlibFormat. Format constructors will be hidden in version 0.7
Raw	Deprecated: Use rawFormat. Format constructors will be hidden in version 0.7
GZipOrZlib	Deprecated: Use gzipOrZlibFormat. Format constructors will be hidden in version 0.7

Instances

Instances details

Bounded Format Source #
Instance details Defined in Codec.Compression.Zlib.Stream Methods minBound :: Format Source # maxBound :: Format Source #
Enum Format Source #
Instance details Defined in Codec.Compression.Zlib.Stream Methods succ :: Format -> Format Source # pred :: Format -> Format Source # toEnum :: Int -> Format Source # fromEnum :: Format -> Int Source # enumFrom :: Format -> [ Format ] Source # enumFromThen :: Format -> Format -> [ Format ] Source # enumFromTo :: Format -> Format -> [ Format ] Source # enumFromThenTo :: Format -> Format -> Format -> [ Format ] Source #
Eq Format Source #
Instance details Defined in Codec.Compression.Zlib.Stream Methods (==) :: Format -> Format -> Bool Source # (/=) :: Format -> Format -> Bool Source #
Ord Format Source #
Instance details Defined in Codec.Compression.Zlib.Stream Methods compare :: Format -> Format -> Ordering Source # (<) :: Format -> Format -> Bool Source # (<=) :: Format -> Format -> Bool Source # (>) :: Format -> Format -> Bool Source # (>=) :: Format -> Format -> Bool Source # max :: Format -> Format -> Format Source # min :: Format -> Format -> Format Source #
Show Format Source #
Instance details Defined in Codec.Compression.Zlib.Stream Methods showsPrec :: Int -> Format -> ShowS Source # show :: Format -> String Source # showList :: [ Format ] -> ShowS Source #
Generic Format Source #
Instance details Defined in Codec.Compression.Zlib.Stream Associated Types type Rep Format :: Type -> Type Source # Methods from :: Format -> Rep Format x Source # to :: Rep Format x -> Format Source #
type Rep Format Source #
Instance details Defined in Codec.Compression.Zlib.Stream type Rep Format = D1 (' MetaData "Format" "Codec.Compression.Zlib.Stream" "zlib-0.6.3.0-90wXp5FStC1FskI4bStJC5" ' False ) (( C1 (' MetaCons "GZip" ' PrefixI ' False ) ( U1 :: Type -> Type ) :+: C1 (' MetaCons "Zlib" ' PrefixI ' False ) ( U1 :: Type -> Type )) :+: ( C1 (' MetaCons "Raw" ' PrefixI ' False ) ( U1 :: Type -> Type ) :+: C1 (' MetaCons "GZipOrZlib" ' PrefixI ' False ) ( U1 :: Type -> Type )))

gzipFormat :: Format Source #

The gzip format uses a header with a checksum and some optional meta-data about the compressed file. It is intended primarily for compressing individual files but is also sometimes used for network protocols such as HTTP. The format is described in detail in RFC #1952 http://www.ietf.org/rfc/rfc1952.txt

zlibFormat :: Format Source #

The zlib format uses a minimal header with a checksum but no other meta-data. It is especially designed for use in network protocols. The format is described in detail in RFC #1950 http://www.ietf.org/rfc/rfc1950.txt

rawFormat :: Format Source #

The 'raw' format is just the compressed data stream without any additional header, meta-data or data-integrity checksum. The format is described in detail in RFC #1951 http://www.ietf.org/rfc/rfc1951.txt

gzipOrZlibFormat :: Format Source #

This is not a format as such. It enabled zlib or gzip decoding with automatic header detection. This only makes sense for decompression.

data CompressionLevel Source #

The compression level parameter controls the amount of compression. This is a trade-off between the amount of compression and the time required to do the compression.

Constructors

DefaultCompression	Deprecated: Use defaultCompression. CompressionLevel constructors will be hidden in version 0.7
NoCompression	Deprecated: Use noCompression. CompressionLevel constructors will be hidden in version 0.7
BestSpeed	Deprecated: Use bestSpeed. CompressionLevel constructors will be hidden in version 0.7
BestCompression	Deprecated: Use bestCompression. CompressionLevel constructors will be hidden in version 0.7
CompressionLevel Int

Instances

Instances details

Eq CompressionLevel Source #
Instance details Defined in Codec.Compression.Zlib.Stream Methods (==) :: CompressionLevel -> CompressionLevel -> Bool Source # (/=) :: CompressionLevel -> CompressionLevel -> Bool Source #
Show CompressionLevel Source #
Instance details Defined in Codec.Compression.Zlib.Stream Methods showsPrec :: Int -> CompressionLevel -> ShowS Source # show :: CompressionLevel -> String Source # showList :: [ CompressionLevel ] -> ShowS Source #
Generic CompressionLevel Source #
Instance details Defined in Codec.Compression.Zlib.Stream Associated Types type Rep CompressionLevel :: Type -> Type Source # Methods from :: CompressionLevel -> Rep CompressionLevel x Source # to :: Rep CompressionLevel x -> CompressionLevel Source #
type Rep CompressionLevel Source #
Instance details Defined in Codec.Compression.Zlib.Stream type Rep CompressionLevel = D1 (' MetaData "CompressionLevel" "Codec.Compression.Zlib.Stream" "zlib-0.6.3.0-90wXp5FStC1FskI4bStJC5" ' False ) (( C1 (' MetaCons "DefaultCompression" ' PrefixI ' False ) ( U1 :: Type -> Type ) :+: C1 (' MetaCons "NoCompression" ' PrefixI ' False ) ( U1 :: Type -> Type )) :+: ( C1 (' MetaCons "BestSpeed" ' PrefixI ' False ) ( U1 :: Type -> Type ) :+: ( C1 (' MetaCons "BestCompression" ' PrefixI ' False ) ( U1 :: Type -> Type ) :+: C1 (' MetaCons "CompressionLevel" ' PrefixI ' False ) ( S1 (' MetaSel (' Nothing :: Maybe Symbol ) ' NoSourceUnpackedness ' NoSourceStrictness ' DecidedLazy ) ( Rec0 Int )))))

defaultCompression :: CompressionLevel Source #

The default compression level is 6 (that is, biased towards higher compression at expense of speed).

noCompression :: CompressionLevel Source #

No compression, just a block copy.

bestSpeed :: CompressionLevel Source #

The fastest compression method (less compression)

bestCompression :: CompressionLevel Source #

The slowest compression method (best compression).

compressionLevel :: Int -> CompressionLevel Source #

A specific compression level between 0 and 9.

data Method Source #

The compression method

Constructors

Deflated

Deprecated: Use deflateMethod. Method constructors will be hidden in version 0.7

Instances

Instances details

Bounded Method Source #
Instance details Defined in Codec.Compression.Zlib.Stream Methods minBound :: Method Source # maxBound :: Method Source #
Enum Method Source #
Instance details Defined in Codec.Compression.Zlib.Stream Methods succ :: Method -> Method Source # pred :: Method -> Method Source # toEnum :: Int -> Method Source # fromEnum :: Method -> Int Source # enumFrom :: Method -> [ Method ] Source # enumFromThen :: Method -> Method -> [ Method ] Source # enumFromTo :: Method -> Method -> [ Method ] Source # enumFromThenTo :: Method -> Method -> Method -> [ Method ] Source #
Eq Method Source #
Instance details Defined in Codec.Compression.Zlib.Stream Methods (==) :: Method -> Method -> Bool Source # (/=) :: Method -> Method -> Bool Source #
Ord Method Source #
Instance details Defined in Codec.Compression.Zlib.Stream Methods compare :: Method -> Method -> Ordering Source # (<) :: Method -> Method -> Bool Source # (<=) :: Method -> Method -> Bool Source # (>) :: Method -> Method -> Bool Source # (>=) :: Method -> Method -> Bool Source # max :: Method -> Method -> Method Source # min :: Method -> Method -> Method Source #
Show Method Source #
Instance details Defined in Codec.Compression.Zlib.Stream Methods showsPrec :: Int -> Method -> ShowS Source # show :: Method -> String Source # showList :: [ Method ] -> ShowS Source #
Generic Method Source #
Instance details Defined in Codec.Compression.Zlib.Stream Associated Types type Rep Method :: Type -> Type Source # Methods from :: Method -> Rep Method x Source # to :: Rep Method x -> Method Source #
type Rep Method Source #
Instance details Defined in Codec.Compression.Zlib.Stream type Rep Method = D1 (' MetaData "Method" "Codec.Compression.Zlib.Stream" "zlib-0.6.3.0-90wXp5FStC1FskI4bStJC5" ' False ) ( C1 (' MetaCons "Deflated" ' PrefixI ' False ) ( U1 :: Type -> Type ))

deflateMethod :: Method Source #

'Deflate' is the only method supported in this version of zlib. Indeed it is likely to be the only method that ever will be supported.

data WindowBits Source #

This specifies the size of the compression window. Larger values of this parameter result in better compression at the expense of higher memory usage.

The compression window size is the value of the the window bits raised to the power 2. The window bits must be in the range 9..15 which corresponds to compression window sizes of 512b to 32Kb. The default is 15 which is also the maximum size.

The total amount of memory used depends on the window bits and the MemoryLevel . See the MemoryLevel for the details.

Constructors

WindowBits Int
DefaultWindowBits	Deprecated: Use defaultWindowBits. WindowBits constructors will be hidden in version 0.7

Instances

Instances details

Eq WindowBits Source #
Instance details Defined in Codec.Compression.Zlib.Stream Methods (==) :: WindowBits -> WindowBits -> Bool Source # (/=) :: WindowBits -> WindowBits -> Bool Source #
Ord WindowBits Source #
Instance details Defined in Codec.Compression.Zlib.Stream Methods compare :: WindowBits -> WindowBits -> Ordering Source # (<) :: WindowBits -> WindowBits -> Bool Source # (<=) :: WindowBits -> WindowBits -> Bool Source # (>) :: WindowBits -> WindowBits -> Bool Source # (>=) :: WindowBits -> WindowBits -> Bool Source # max :: WindowBits -> WindowBits -> WindowBits Source # min :: WindowBits -> WindowBits -> WindowBits Source #
Show WindowBits Source #
Instance details Defined in Codec.Compression.Zlib.Stream Methods showsPrec :: Int -> WindowBits -> ShowS Source # show :: WindowBits -> String Source # showList :: [ WindowBits ] -> ShowS Source #
Generic WindowBits Source #
Instance details Defined in Codec.Compression.Zlib.Stream Associated Types type Rep WindowBits :: Type -> Type Source # Methods from :: WindowBits -> Rep WindowBits x Source # to :: Rep WindowBits x -> WindowBits Source #
type Rep WindowBits Source #
Instance details Defined in Codec.Compression.Zlib.Stream type Rep WindowBits = D1 (' MetaData "WindowBits" "Codec.Compression.Zlib.Stream" "zlib-0.6.3.0-90wXp5FStC1FskI4bStJC5" ' False ) ( C1 (' MetaCons "WindowBits" ' PrefixI ' False ) ( S1 (' MetaSel (' Nothing :: Maybe Symbol ) ' NoSourceUnpackedness ' NoSourceStrictness ' DecidedLazy ) ( Rec0 Int )) :+: C1 (' MetaCons "DefaultWindowBits" ' PrefixI ' False ) ( U1 :: Type -> Type ))

defaultWindowBits :: WindowBits Source #

The default WindowBits is 15 which is also the maximum size.

windowBits :: Int -> WindowBits Source #

A specific compression window size, specified in bits in the range 9..15

data MemoryLevel Source #

The MemoryLevel parameter specifies how much memory should be allocated for the internal compression state. It is a tradeoff between memory usage, compression ratio and compression speed. Using more memory allows faster compression and a better compression ratio.

The total amount of memory used for compression depends on the WindowBits and the MemoryLevel . For decompression it depends only on the WindowBits . The totals are given by the functions:

compressTotal windowBits memLevel = 4 * 2^windowBits + 512 * 2^memLevel
decompressTotal windowBits = 2^windowBits

For example, for compression with the default windowBits = 15 and memLevel = 8 uses 256Kb . So for example a network server with 100 concurrent compressed streams would use 25Mb . The memory per stream can be halved (at the cost of somewhat degraded and slower compression) by reducing the windowBits and memLevel by one.

Decompression takes less memory, the default windowBits = 15 corresponds to just 32Kb .

Constructors

DefaultMemoryLevel	Deprecated: Use defaultMemoryLevel. MemoryLevel constructors will be hidden in version 0.7
MinMemoryLevel	Deprecated: Use minMemoryLevel. MemoryLevel constructors will be hidden in version 0.7
MaxMemoryLevel	Deprecated: Use maxMemoryLevel. MemoryLevel constructors will be hidden in version 0.7
MemoryLevel Int

Instances

Instances details

Eq MemoryLevel Source #
Instance details Defined in Codec.Compression.Zlib.Stream Methods (==) :: MemoryLevel -> MemoryLevel -> Bool Source # (/=) :: MemoryLevel -> MemoryLevel -> Bool Source #
Show MemoryLevel Source #
Instance details Defined in Codec.Compression.Zlib.Stream Methods showsPrec :: Int -> MemoryLevel -> ShowS Source # show :: MemoryLevel -> String Source # showList :: [ MemoryLevel ] -> ShowS Source #
Generic MemoryLevel Source #
Instance details Defined in Codec.Compression.Zlib.Stream Associated Types type Rep MemoryLevel :: Type -> Type Source # Methods from :: MemoryLevel -> Rep MemoryLevel x Source # to :: Rep MemoryLevel x -> MemoryLevel Source #
type Rep MemoryLevel Source #
Instance details Defined in Codec.Compression.Zlib.Stream type Rep MemoryLevel = D1 (' MetaData "MemoryLevel" "Codec.Compression.Zlib.Stream" "zlib-0.6.3.0-90wXp5FStC1FskI4bStJC5" ' False ) (( C1 (' MetaCons "DefaultMemoryLevel" ' PrefixI ' False ) ( U1 :: Type -> Type ) :+: C1 (' MetaCons "MinMemoryLevel" ' PrefixI ' False ) ( U1 :: Type -> Type )) :+: ( C1 (' MetaCons "MaxMemoryLevel" ' PrefixI ' False ) ( U1 :: Type -> Type ) :+: C1 (' MetaCons "MemoryLevel" ' PrefixI ' False ) ( S1 (' MetaSel (' Nothing :: Maybe Symbol ) ' NoSourceUnpackedness ' NoSourceStrictness ' DecidedLazy ) ( Rec0 Int ))))

defaultMemoryLevel :: MemoryLevel Source #

The default memory level. (Equivalent to memoryLevel 8 )

minMemoryLevel :: MemoryLevel Source #

Use minimum memory. This is slow and reduces the compression ratio. (Equivalent to memoryLevel 1 )

maxMemoryLevel :: MemoryLevel Source #

Use maximum memory for optimal compression speed. (Equivalent to memoryLevel 9 )

memoryLevel :: Int -> MemoryLevel Source #

A specific level in the range 1..9

data CompressionStrategy Source #

The strategy parameter is used to tune the compression algorithm.

The strategy parameter only affects the compression ratio but not the correctness of the compressed output even if it is not set appropriately.

Constructors

DefaultStrategy	Deprecated: Use defaultStrategy. CompressionStrategy constructors will be hidden in version 0.7
Filtered	Deprecated: Use filteredStrategy. CompressionStrategy constructors will be hidden in version 0.7
HuffmanOnly	Deprecated: Use huffmanOnlyStrategy. CompressionStrategy constructors will be hidden in version 0.7

Instances

Instances details

Bounded CompressionStrategy Source #
Instance details Defined in Codec.Compression.Zlib.Stream Methods minBound :: CompressionStrategy Source # maxBound :: CompressionStrategy Source #
Enum CompressionStrategy Source #
Instance details Defined in Codec.Compression.Zlib.Stream Methods succ :: CompressionStrategy -> CompressionStrategy Source # pred :: CompressionStrategy -> CompressionStrategy Source # toEnum :: Int -> CompressionStrategy Source # fromEnum :: CompressionStrategy -> Int Source # enumFrom :: CompressionStrategy -> [ CompressionStrategy ] Source # enumFromThen :: CompressionStrategy -> CompressionStrategy -> [ CompressionStrategy ] Source # enumFromTo :: CompressionStrategy -> CompressionStrategy -> [ CompressionStrategy ] Source # enumFromThenTo :: CompressionStrategy -> CompressionStrategy -> CompressionStrategy -> [ CompressionStrategy ] Source #
Eq CompressionStrategy Source #
Instance details Defined in Codec.Compression.Zlib.Stream Methods (==) :: CompressionStrategy -> CompressionStrategy -> Bool Source # (/=) :: CompressionStrategy -> CompressionStrategy -> Bool Source #
Ord CompressionStrategy Source #
Instance details Defined in Codec.Compression.Zlib.Stream Methods compare :: CompressionStrategy -> CompressionStrategy -> Ordering Source # (<) :: CompressionStrategy -> CompressionStrategy -> Bool Source # (<=) :: CompressionStrategy -> CompressionStrategy -> Bool Source # (>) :: CompressionStrategy -> CompressionStrategy -> Bool Source # (>=) :: CompressionStrategy -> CompressionStrategy -> Bool Source # max :: CompressionStrategy -> CompressionStrategy -> CompressionStrategy Source # min :: CompressionStrategy -> CompressionStrategy -> CompressionStrategy Source #
Show CompressionStrategy Source #
Instance details Defined in Codec.Compression.Zlib.Stream Methods showsPrec :: Int -> CompressionStrategy -> ShowS Source # show :: CompressionStrategy -> String Source # showList :: [ CompressionStrategy ] -> ShowS Source #
Generic CompressionStrategy Source #
Instance details Defined in Codec.Compression.Zlib.Stream Associated Types type Rep CompressionStrategy :: Type -> Type Source # Methods from :: CompressionStrategy -> Rep CompressionStrategy x Source # to :: Rep CompressionStrategy x -> CompressionStrategy Source #
type Rep CompressionStrategy Source #
Instance details Defined in Codec.Compression.Zlib.Stream type Rep CompressionStrategy = D1 (' MetaData "CompressionStrategy" "Codec.Compression.Zlib.Stream" "zlib-0.6.3.0-90wXp5FStC1FskI4bStJC5" ' False ) ( C1 (' MetaCons "DefaultStrategy" ' PrefixI ' False ) ( U1 :: Type -> Type ) :+: ( C1 (' MetaCons "Filtered" ' PrefixI ' False ) ( U1 :: Type -> Type ) :+: C1 (' MetaCons "HuffmanOnly" ' PrefixI ' False ) ( U1 :: Type -> Type )))

defaultStrategy :: CompressionStrategy Source #

Use this default compression strategy for normal data.

filteredStrategy :: CompressionStrategy Source #

Use the filtered compression strategy for data produced by a filter (or predictor). Filtered data consists mostly of small values with a somewhat random distribution. In this case, the compression algorithm is tuned to compress them better. The effect of this strategy is to force more Huffman coding and less string matching; it is somewhat intermediate between defaultCompressionStrategy and huffmanOnlyCompressionStrategy .

huffmanOnlyStrategy :: CompressionStrategy Source #

Use the Huffman-only compression strategy to force Huffman encoding only (no string match).