----------------------------------------------------------------------------- -- | -- Copyright : (c) 2006-2008 Duncan Coutts -- License : BSD-style -- -- Maintainer : duncan@haskell.org -- Stability : provisional -- Portability : portable (H98 + FFI) -- -- Compression and decompression of data streams in the zlib format. -- -- The format is described in detail in RFC #1950: -- <http://www.ietf.org/rfc/rfc1950.txt> -- -- See also the zlib home page: <http://zlib.net/> -- ----------------------------------------------------------------------------- module Codec.Compression.Zlib ( -- | This module provides pure functions for compressing and decompressing -- streams of data in the zlib format and represented by lazy 'ByteString's. -- This makes it easy to use either in memory or with disk or network IO. -- * Simple compression and decompression compress, decompress, -- * Extended api with control over compression parameters compressWith, decompressWith, CompressParams(..), defaultCompressParams, DecompressParams(..), defaultDecompressParams, -- ** The compression parameter types CompressionLevel(..), defaultCompression, noCompression, bestSpeed, bestCompression, compressionLevel, Method(..), deflateMethod, WindowBits(..), defaultWindowBits, windowBits, MemoryLevel(..), defaultMemoryLevel, minMemoryLevel, maxMemoryLevel, memoryLevel, CompressionStrategy(..), defaultStrategy, filteredStrategy, huffmanOnlyStrategy, ) where import Data.ByteString.Lazy (ByteString) import qualified Codec.Compression.Zlib.Internal as Internal import Codec.Compression.Zlib.Internal hiding (compress, decompress) -- | Decompress a stream of data in the zlib format. -- -- There are a number of errors that can occur. In each case an exception will -- be thrown. The possible error conditions are: -- -- * if the stream does not start with a valid gzip header -- -- * if the compressed stream is corrupted -- -- * if the compressed stream ends permaturely -- -- Note that the decompression is performed /lazily/. Errors in the data stream -- may not be detected until the end of the stream is demanded (since it is -- only at the end that the final checksum can be checked). If this is -- important to you, you must make sure to consume the whole decompressed -- stream before doing any IO action that depends on it. -- decompress :: ByteString -> ByteString decompress = decompressWith defaultDecompressParams -- | Like 'decompress' but with the ability to specify various decompression -- parameters. Typical usage: -- -- > decompressWith defaultCompressParams { ... } -- decompressWith :: DecompressParams -> ByteString -> ByteString decompressWith = Internal.decompress zlibFormat -- | Compress a stream of data into the zlib format. -- -- This uses the default compression parameters. In partiular it uses the -- default compression level which favours a higher compression ratio over -- compression speed, though it does not use the maximum compression level. -- -- Use 'compressWith' to adjust the compression level or other compression -- parameters. -- compress :: ByteString -> ByteString compress = compressWith defaultCompressParams -- | Like 'compress' but with the ability to specify various compression -- parameters. Typical usage: -- -- > compressWith defaultCompressParams { ... } -- -- In particular you can set the compression level: -- -- > compressWith defaultCompressParams { compressLevel = BestCompression } -- compressWith :: CompressParams -> ByteString -> ByteString compressWith = Internal.compress zlibFormat