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<pre><a name="line-1"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span>
<a name="line-2"></a><span class='hs-comment'>-- |</span>
<a name="line-3"></a><span class='hs-comment'>-- Copyright : (c) 2006-2008 Duncan Coutts</span>
<a name="line-4"></a><span class='hs-comment'>-- License : BSD-style</span>
<a name="line-5"></a><span class='hs-comment'>--</span>
<a name="line-6"></a><span class='hs-comment'>-- Maintainer : duncan@haskell.org</span>
<a name="line-7"></a><span class='hs-comment'>-- Stability : provisional</span>
<a name="line-8"></a><span class='hs-comment'>-- Portability : portable (H98 + FFI)</span>
<a name="line-9"></a><span class='hs-comment'>--</span>
<a name="line-10"></a><span class='hs-comment'>-- Compression and decompression of data streams in the gzip format.</span>
<a name="line-11"></a><span class='hs-comment'>--</span>
<a name="line-12"></a><span class='hs-comment'>-- The format is described in detail in RFC #1952:</span>
<a name="line-13"></a><span class='hs-comment'>-- <<a href="http://www.ietf.org/rfc/rfc1952.txt">http://www.ietf.org/rfc/rfc1952.txt</a>></span>
<a name="line-14"></a><span class='hs-comment'>--</span>
<a name="line-15"></a><span class='hs-comment'>-- See also the zlib home page: <<a href="http://zlib.net/">http://zlib.net/</a>></span>
<a name="line-16"></a><span class='hs-comment'>--</span>
<a name="line-17"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span>
<a name="line-18"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>Codec</span><span class='hs-varop'>.</span><span class='hs-conid'>Compression</span><span class='hs-varop'>.</span><span class='hs-conid'>GZip</span> <span class='hs-layout'>(</span>
<a name="line-19"></a>
<a name="line-20"></a> <span class='hs-comment'>-- | This module provides pure functions for compressing and decompressing</span>
<a name="line-21"></a> <span class='hs-comment'>-- streams of data in the gzip format and represented by lazy 'ByteString's.</span>
<a name="line-22"></a> <span class='hs-comment'>-- This makes it easy to use either in memory or with disk or network IO.</span>
<a name="line-23"></a> <span class='hs-comment'>--</span>
<a name="line-24"></a> <span class='hs-comment'>-- For example a simple gzip compression program is just:</span>
<a name="line-25"></a> <span class='hs-comment'>--</span>
<a name="line-26"></a> <span class='hs-comment'>-- > import qualified Data.ByteString.Lazy as ByteString</span>
<a name="line-27"></a> <span class='hs-comment'>-- > import qualified Codec.Compression.GZip as GZip</span>
<a name="line-28"></a> <span class='hs-comment'>-- ></span>
<a name="line-29"></a> <span class='hs-comment'>-- > main = ByteString.interact GZip.compress</span>
<a name="line-30"></a> <span class='hs-comment'>--</span>
<a name="line-31"></a> <span class='hs-comment'>-- Or you could lazily read in and decompress a @.gz@ file using:</span>
<a name="line-32"></a> <span class='hs-comment'>--</span>
<a name="line-33"></a> <span class='hs-comment'>-- > content <- fmap GZip.decompress (readFile file)</span>
<a name="line-34"></a> <span class='hs-comment'>--</span>
<a name="line-35"></a>
<a name="line-36"></a> <span class='hs-comment'>-- * Simple compression and decompression</span>
<a name="line-37"></a> <span class='hs-varid'>compress</span><span class='hs-layout'>,</span>
<a name="line-38"></a> <span class='hs-varid'>decompress</span><span class='hs-layout'>,</span>
<a name="line-39"></a>
<a name="line-40"></a> <span class='hs-comment'>-- * Extended api with control over compression parameters</span>
<a name="line-41"></a> <span class='hs-varid'>compressWith</span><span class='hs-layout'>,</span>
<a name="line-42"></a> <span class='hs-varid'>decompressWith</span><span class='hs-layout'>,</span>
<a name="line-43"></a>
<a name="line-44"></a> <span class='hs-conid'>CompressParams</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span> <span class='hs-varid'>defaultCompressParams</span><span class='hs-layout'>,</span>
<a name="line-45"></a> <span class='hs-conid'>DecompressParams</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span> <span class='hs-varid'>defaultDecompressParams</span><span class='hs-layout'>,</span>
<a name="line-46"></a>
<a name="line-47"></a> <span class='hs-comment'>-- ** The compression parameter types</span>
<a name="line-48"></a> <span class='hs-conid'>CompressionLevel</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-49"></a> <span class='hs-varid'>defaultCompression</span><span class='hs-layout'>,</span>
<a name="line-50"></a> <span class='hs-varid'>noCompression</span><span class='hs-layout'>,</span>
<a name="line-51"></a> <span class='hs-varid'>bestSpeed</span><span class='hs-layout'>,</span>
<a name="line-52"></a> <span class='hs-varid'>bestCompression</span><span class='hs-layout'>,</span>
<a name="line-53"></a> <span class='hs-varid'>compressionLevel</span><span class='hs-layout'>,</span>
<a name="line-54"></a> <span class='hs-conid'>Method</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-55"></a> <span class='hs-varid'>deflateMethod</span><span class='hs-layout'>,</span>
<a name="line-56"></a> <span class='hs-conid'>WindowBits</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-57"></a> <span class='hs-varid'>defaultWindowBits</span><span class='hs-layout'>,</span>
<a name="line-58"></a> <span class='hs-varid'>windowBits</span><span class='hs-layout'>,</span>
<a name="line-59"></a> <span class='hs-conid'>MemoryLevel</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-60"></a> <span class='hs-varid'>defaultMemoryLevel</span><span class='hs-layout'>,</span>
<a name="line-61"></a> <span class='hs-varid'>minMemoryLevel</span><span class='hs-layout'>,</span>
<a name="line-62"></a> <span class='hs-varid'>maxMemoryLevel</span><span class='hs-layout'>,</span>
<a name="line-63"></a> <span class='hs-varid'>memoryLevel</span><span class='hs-layout'>,</span>
<a name="line-64"></a> <span class='hs-conid'>CompressionStrategy</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-65"></a> <span class='hs-varid'>defaultStrategy</span><span class='hs-layout'>,</span>
<a name="line-66"></a> <span class='hs-varid'>filteredStrategy</span><span class='hs-layout'>,</span>
<a name="line-67"></a> <span class='hs-varid'>huffmanOnlyStrategy</span><span class='hs-layout'>,</span>
<a name="line-68"></a>
<a name="line-69"></a> <span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-70"></a>
<a name="line-71"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>ByteString</span><span class='hs-varop'>.</span><span class='hs-conid'>Lazy</span> <span class='hs-layout'>(</span><span class='hs-conid'>ByteString</span><span class='hs-layout'>)</span>
<a name="line-72"></a>
<a name="line-73"></a><span class='hs-keyword'>import</span> <span class='hs-keyword'>qualified</span> <span class='hs-conid'>Codec</span><span class='hs-varop'>.</span><span class='hs-conid'>Compression</span><span class='hs-varop'>.</span><span class='hs-conid'>Zlib</span><span class='hs-varop'>.</span><span class='hs-conid'>Internal</span> <span class='hs-keyword'>as</span> <span class='hs-conid'>Internal</span>
<a name="line-74"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Codec</span><span class='hs-varop'>.</span><span class='hs-conid'>Compression</span><span class='hs-varop'>.</span><span class='hs-conid'>Zlib</span><span class='hs-varop'>.</span><span class='hs-conid'>Internal</span> <span class='hs-varid'>hiding</span> <span class='hs-layout'>(</span><span class='hs-varid'>compress</span><span class='hs-layout'>,</span> <span class='hs-varid'>decompress</span><span class='hs-layout'>)</span>
<a name="line-75"></a>
<a name="line-76"></a>
<a name="line-77"></a><a name="decompress"></a><span class='hs-comment'>-- | Decompress a stream of data in the gzip format.</span>
<a name="line-78"></a><span class='hs-comment'>--</span>
<a name="line-79"></a><span class='hs-comment'>-- There are a number of errors that can occur. In each case an exception will</span>
<a name="line-80"></a><span class='hs-comment'>-- be thrown. The possible error conditions are:</span>
<a name="line-81"></a><span class='hs-comment'>--</span>
<a name="line-82"></a><span class='hs-comment'>-- * if the stream does not start with a valid gzip header</span>
<a name="line-83"></a><span class='hs-comment'>--</span>
<a name="line-84"></a><span class='hs-comment'>-- * if the compressed stream is corrupted</span>
<a name="line-85"></a><span class='hs-comment'>--</span>
<a name="line-86"></a><span class='hs-comment'>-- * if the compressed stream ends permaturely</span>
<a name="line-87"></a><span class='hs-comment'>--</span>
<a name="line-88"></a><span class='hs-comment'>-- Note that the decompression is performed /lazily/. Errors in the data stream</span>
<a name="line-89"></a><span class='hs-comment'>-- may not be detected until the end of the stream is demanded (since it is</span>
<a name="line-90"></a><span class='hs-comment'>-- only at the end that the final checksum can be checked). If this is</span>
<a name="line-91"></a><span class='hs-comment'>-- important to you, you must make sure to consume the whole decompressed</span>
<a name="line-92"></a><span class='hs-comment'>-- stream before doing any IO action that depends on it.</span>
<a name="line-93"></a><span class='hs-comment'>--</span>
<a name="line-94"></a><span class='hs-definition'>decompress</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>ByteString</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>ByteString</span>
<a name="line-95"></a><span class='hs-definition'>decompress</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>decompressWith</span> <span class='hs-varid'>defaultDecompressParams</span>
<a name="line-96"></a>
<a name="line-97"></a>
<a name="line-98"></a><a name="decompressWith"></a><span class='hs-comment'>-- | Like 'decompress' but with the ability to specify various decompression</span>
<a name="line-99"></a><span class='hs-comment'>-- parameters. Typical usage:</span>
<a name="line-100"></a><span class='hs-comment'>--</span>
<a name="line-101"></a><span class='hs-comment'>-- > decompressWith defaultCompressParams { ... }</span>
<a name="line-102"></a><span class='hs-comment'>--</span>
<a name="line-103"></a><span class='hs-definition'>decompressWith</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>DecompressParams</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>ByteString</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>ByteString</span>
<a name="line-104"></a><span class='hs-definition'>decompressWith</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Internal</span><span class='hs-varop'>.</span><span class='hs-varid'>decompress</span> <span class='hs-varid'>gzipFormat</span>
<a name="line-105"></a>
<a name="line-106"></a>
<a name="line-107"></a><a name="compress"></a><span class='hs-comment'>-- | Compress a stream of data into the gzip format.</span>
<a name="line-108"></a><span class='hs-comment'>--</span>
<a name="line-109"></a><span class='hs-comment'>-- This uses the default compression parameters. In partiular it uses the</span>
<a name="line-110"></a><span class='hs-comment'>-- default compression level which favours a higher compression ratio over</span>
<a name="line-111"></a><span class='hs-comment'>-- compression speed, though it does not use the maximum compression level.</span>
<a name="line-112"></a><span class='hs-comment'>--</span>
<a name="line-113"></a><span class='hs-comment'>-- Use 'compressWith' to adjust the compression level or other compression</span>
<a name="line-114"></a><span class='hs-comment'>-- parameters.</span>
<a name="line-115"></a><span class='hs-comment'>--</span>
<a name="line-116"></a><span class='hs-definition'>compress</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>ByteString</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>ByteString</span>
<a name="line-117"></a><span class='hs-definition'>compress</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>compressWith</span> <span class='hs-varid'>defaultCompressParams</span>
<a name="line-118"></a>
<a name="line-119"></a>
<a name="line-120"></a><a name="compressWith"></a><span class='hs-comment'>-- | Like 'compress' but with the ability to specify various compression</span>
<a name="line-121"></a><span class='hs-comment'>-- parameters. Typical usage:</span>
<a name="line-122"></a><span class='hs-comment'>--</span>
<a name="line-123"></a><span class='hs-comment'>-- > compressWith defaultCompressParams { ... }</span>
<a name="line-124"></a><span class='hs-comment'>--</span>
<a name="line-125"></a><span class='hs-comment'>-- In particular you can set the compression level:</span>
<a name="line-126"></a><span class='hs-comment'>--</span>
<a name="line-127"></a><span class='hs-comment'>-- > compressWith defaultCompressParams { compressLevel = BestCompression }</span>
<a name="line-128"></a><span class='hs-comment'>--</span>
<a name="line-129"></a><span class='hs-definition'>compressWith</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>CompressParams</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>ByteString</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>ByteString</span>
<a name="line-130"></a><span class='hs-definition'>compressWith</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Internal</span><span class='hs-varop'>.</span><span class='hs-varid'>compress</span> <span class='hs-varid'>gzipFormat</span>
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