117 lines
3.5 KiB
Haskell
117 lines
3.5 KiB
Haskell
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-----------------------------------------------------------------------------
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-- |
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-- Copyright : (c) 2006-2014 Duncan Coutts
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-- License : BSD-style
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--
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-- Maintainer : duncan@community.haskell.org
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--
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-- Compression and decompression of data streams in the zlib format.
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--
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-- The format is described in detail in RFC #1950:
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-- <http://www.ietf.org/rfc/rfc1950.txt>
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--
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-- See also the zlib home page: <http://zlib.net/>
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--
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-----------------------------------------------------------------------------
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module Codec.Compression.Zlib (
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-- | This module provides pure functions for compressing and decompressing
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-- streams of data in the zlib format and represented by lazy 'ByteString's.
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-- This makes it easy to use either in memory or with disk or network IO.
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-- * Simple compression and decompression
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compress,
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decompress,
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-- * Extended api with control over compression parameters
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compressWith,
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decompressWith,
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CompressParams(..), defaultCompressParams,
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DecompressParams(..), defaultDecompressParams,
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-- ** The compression parameter types
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CompressionLevel(..),
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defaultCompression,
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noCompression,
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bestSpeed,
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bestCompression,
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compressionLevel,
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Method(..),
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deflateMethod,
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WindowBits(..),
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defaultWindowBits,
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windowBits,
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MemoryLevel(..),
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defaultMemoryLevel,
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minMemoryLevel,
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maxMemoryLevel,
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memoryLevel,
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CompressionStrategy(..),
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defaultStrategy,
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filteredStrategy,
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huffmanOnlyStrategy,
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) where
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import Data.ByteString.Lazy (ByteString)
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import qualified Codec.Compression.Zlib.Internal as Internal
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import Codec.Compression.Zlib.Internal hiding (compress, decompress)
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-- | Decompress a stream of data in the zlib format.
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--
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-- There are a number of errors that can occur. In each case an exception will
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-- be thrown. The possible error conditions are:
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--
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-- * if the stream does not start with a valid gzip header
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--
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-- * if the compressed stream is corrupted
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--
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-- * if the compressed stream ends permaturely
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--
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-- Note that the decompression is performed /lazily/. Errors in the data stream
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-- may not be detected until the end of the stream is demanded (since it is
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-- only at the end that the final checksum can be checked). If this is
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-- important to you, you must make sure to consume the whole decompressed
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-- stream before doing any IO action that depends on it.
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--
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decompress :: ByteString -> ByteString
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decompress = decompressWith defaultDecompressParams
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-- | Like 'decompress' but with the ability to specify various decompression
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-- parameters. Typical usage:
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--
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-- > decompressWith defaultCompressParams { ... }
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--
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decompressWith :: DecompressParams -> ByteString -> ByteString
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decompressWith = Internal.decompress zlibFormat
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-- | Compress a stream of data into the zlib format.
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--
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-- This uses the default compression parameters. In partiular it uses the
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-- default compression level which favours a higher compression ratio over
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-- compression speed, though it does not use the maximum compression level.
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--
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-- Use 'compressWith' to adjust the compression level or other compression
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-- parameters.
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--
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compress :: ByteString -> ByteString
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compress = compressWith defaultCompressParams
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-- | Like 'compress' but with the ability to specify various compression
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-- parameters. Typical usage:
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--
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-- > compressWith defaultCompressParams { ... }
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--
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-- In particular you can set the compression level:
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--
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-- > compressWith defaultCompressParams { compressLevel = BestCompression }
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--
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compressWith :: CompressParams -> ByteString -> ByteString
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compressWith = Internal.compress zlibFormat
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