| Copyright | (c) 2006-2014 Duncan Coutts |
|---|---|
| License | BSD-style |
| Maintainer | duncan@community.haskell.org |
| Safe Haskell | Safe |
| Language | Haskell2010 |
Codec.Compression.Zlib.Raw
Contents
Description
Compression and decompression of data streams in the raw deflate format.
The format is described in detail in RFC #1951: http://www.ietf.org/rfc/rfc1951.txt
See also the zlib home page: http://zlib.net/
Synopsis
- compress :: ByteString -> ByteString
- decompress :: ByteString -> ByteString
- compressWith :: CompressParams -> ByteString -> ByteString
- decompressWith :: DecompressParams -> ByteString -> ByteString
- data CompressParams = CompressParams {}
- defaultCompressParams :: CompressParams
- data DecompressParams = DecompressParams {}
- defaultDecompressParams :: DecompressParams
- data CompressionLevel
- defaultCompression :: CompressionLevel
- noCompression :: CompressionLevel
- bestSpeed :: CompressionLevel
- bestCompression :: CompressionLevel
- compressionLevel :: Int -> CompressionLevel
- data Method = Deflated
- deflateMethod :: Method
- data WindowBits
- defaultWindowBits :: WindowBits
- windowBits :: Int -> WindowBits
- data MemoryLevel
- defaultMemoryLevel :: MemoryLevel
- minMemoryLevel :: MemoryLevel
- maxMemoryLevel :: MemoryLevel
- memoryLevel :: Int -> MemoryLevel
- data CompressionStrategy
- defaultStrategy :: CompressionStrategy
- filteredStrategy :: CompressionStrategy
- huffmanOnlyStrategy :: CompressionStrategy
Simple compression and decompression
compress :: ByteString -> ByteString Source #
decompress :: ByteString -> ByteString Source #
Extended api with control over compression parameters
compressWith :: CompressParams -> ByteString -> ByteString Source #
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 extimate is wrong it does
not matter too much, the default buffer size will be used for the remaining
chunks.
Constructors
| CompressParams | |
Instances
| Show CompressParams Source # | |
Defined in Codec.Compression.Zlib.Internal Methods showsPrec :: Int -> CompressParams -> ShowS # show :: CompressParams -> String # showList :: [CompressParams] -> ShowS # | |
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
extimate 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 deccompression functions
use lazy ByteStrings 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 | |
Instances
| Show DecompressParams Source # | |
Defined in Codec.Compression.Zlib.Internal Methods showsPrec :: Int -> DecompressParams -> ShowS # show :: DecompressParams -> String # showList :: [DecompressParams] -> ShowS # | |
defaultDecompressParams :: DecompressParams Source #
The default set of parameters for decompression. This is typically used with
the compressWith function with specific parameters overridden.
The compression parameter types
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
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.
The compression method
Constructors
| Deflated | Deprecated: Use deflateMethod. Method constructors will be hidden in version 0.7 |
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
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 tradoff 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 compressionby) 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
| Eq MemoryLevel Source # | |
Defined in Codec.Compression.Zlib.Stream | |
| Show MemoryLevel Source # | |
Defined in Codec.Compression.Zlib.Stream Methods showsPrec :: Int -> MemoryLevel -> ShowS # show :: MemoryLevel -> String # showList :: [MemoryLevel] -> ShowS # | |
| Generic MemoryLevel Source # | |
Defined in Codec.Compression.Zlib.Stream Associated Types type Rep MemoryLevel :: Type -> Type # | |
| type Rep MemoryLevel Source # | |
Defined in Codec.Compression.Zlib.Stream type Rep MemoryLevel = D1 (MetaData "MemoryLevel" "Codec.Compression.Zlib.Stream" "zlib-0.6.2.1-JkgnCzQLE4d9AnItMNCDCp" 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
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).