<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Codec.Compression.Zlib.Raw</title><link href="ocean.css" rel="stylesheet" type="text/css" title="Ocean" /><script src="haddock-util.js" type="text/javascript"></script><script type="text/javascript">//<![CDATA[ window.onload = function () {pageLoad();setSynopsis("mini_Codec-Compression-Zlib-Raw.html");}; //]]> </script></head><body><div id="package-header"><ul class="links" id="page-menu"><li><a href="src/Codec-Compression-Zlib-Raw.html">Source</a></li><li><a href="index.html">Contents</a></li><li><a href="doc-index.html">Index</a></li></ul><p class="caption">zlib-0.5.3.1: Compression and decompression in the gzip and zlib formats</p></div><div id="content"><div id="module-header"><table class="info"><tr><th>Portability</th><td>portable (H98 + FFI)</td></tr><tr><th>Stability</th><td>provisional</td></tr><tr><th>Maintainer</th><td>duncan@haskell.org</td></tr></table><p class="caption">Codec.Compression.Zlib.Raw</p></div><div id="table-of-contents"><p class="caption">Contents</p><ul><li><a href="#g:1">Simple compression and decompression </a></li><li><a href="#g:2">Extended api with control over compression parameters </a><ul><li><a href="#g:3">The compression parameter types </a></li></ul></li></ul></div><div id="description"><p class="caption">Description</p><div class="doc"><p>Compression and decompression of data streams in the raw deflate format. </p><p>The format is described in detail in RFC #1951: <a href="http://www.ietf.org/rfc/rfc1951.txt">http://www.ietf.org/rfc/rfc1951.txt</a> </p><p>See also the zlib home page: <a href="http://zlib.net/">http://zlib.net/</a> </p></div></div><div id="synopsis"><p id="control.syn" class="caption expander" onclick="toggleSection('syn')">Synopsis</p><ul id="section.syn" class="hide" onclick="toggleSection('syn')"><li class="src short"><a href="#v:compress">compress</a> :: <a href="/usr/share/doc/ghc/html/libraries/bytestring-0.9.1.10/Data-ByteString-Lazy.html#t:ByteString">ByteString</a> -> <a href="/usr/share/doc/ghc/html/libraries/bytestring-0.9.1.10/Data-ByteString-Lazy.html#t:ByteString">ByteString</a></li><li class="src short"><a href="#v:decompress">decompress</a> :: <a href="/usr/share/doc/ghc/html/libraries/bytestring-0.9.1.10/Data-ByteString-Lazy.html#t:ByteString">ByteString</a> -> <a href="/usr/share/doc/ghc/html/libraries/bytestring-0.9.1.10/Data-ByteString-Lazy.html#t:ByteString">ByteString</a></li><li class="src short"><a href="#v:compressWith">compressWith</a> :: <a href="Codec-Compression-Zlib-Raw.html#t:CompressParams">CompressParams</a> -> <a href="/usr/share/doc/ghc/html/libraries/bytestring-0.9.1.10/Data-ByteString-Lazy.html#t:ByteString">ByteString</a> -> <a href="/usr/share/doc/ghc/html/libraries/bytestring-0.9.1.10/Data-ByteString-Lazy.html#t:ByteString">ByteString</a></li><li class="src short"><a href="#v:decompressWith">decompressWith</a> :: <a href="Codec-Compression-Zlib-Raw.html#t:DecompressParams">DecompressParams</a> -> <a href="/usr/share/doc/ghc/html/libraries/bytestring-0.9.1.10/Data-ByteString-Lazy.html#t:ByteString">ByteString</a> -> <a href="/usr/share/doc/ghc/html/libraries/bytestring-0.9.1.10/Data-ByteString-Lazy.html#t:ByteString">ByteString</a></li><li class="src short"><span class="keyword">data</span> <a href="#t:CompressParams">CompressParams</a> = <a href="#v:CompressParams">CompressParams</a> {<ul class="subs"><li><a href="#v:compressLevel">compressLevel</a> :: !<a href="Codec-Compression-Zlib-Raw.html#t:CompressionLevel">CompressionLevel</a></li><li><a href="#v:compressMethod">compressMethod</a> :: !<a href="Codec-Compression-Zlib-Raw.html#t:Method">Method</a></li><li><a href="#v:compressWindowBits">compressWindowBits</a> :: !<a href="Codec-Compression-Zlib-Raw.html#t:WindowBits">WindowBits</a></li><li><a href="#v:compressMemoryLevel">compressMemoryLevel</a> :: !<a href="Codec-Compression-Zlib-Raw.html#t:MemoryLevel">MemoryLevel</a></li><li><a href="#v:compressStrategy">compressStrategy</a> :: !<a href="Codec-Compression-Zlib-Raw.html#t:CompressionStrategy">CompressionStrategy</a></li><li><a href="#v:compressBufferSize">compressBufferSize</a> :: !<a href="/usr/share/doc/ghc/html/libraries/base-4.3.1.0/Data-Int.html#t:Int">Int</a></li></ul>}</li><li class="src short"><a href="#v:defaultCompressParams">defaultCompressParams</a> :: <a href="Codec-Compression-Zlib-Raw.html#t:CompressParams">CompressParams</a></li><li class="src short"><span class="keyword">data</span> <a href="#t:DecompressParams">DecompressParams</a> = <a href="#v:DecompressParams">DecompressParams</a> {<ul class="subs"><li><a href="#v:decompressWindowBits">decompressWindowBits</a> :: !<a href="Codec-Compression-Zlib-Raw.html#t:WindowBits">WindowBits</a></li><li><a href="#v:decompressBufferSize">decompressBufferSize</a> :: !<a href="/usr/share/doc/ghc/html/libraries/base-4.3.1.0/Data-Int.html#t:Int">Int</a></li></ul>}</li><li class="src short"><a href="#v:defaultDecompressParams">defaultDecompressParams</a> :: <a href="Codec-Compression-Zlib-Raw.html#t:DecompressParams">DecompressParams</a></li><li class="src short"><span class="keyword">data</span> <a href="#t:CompressionLevel">CompressionLevel</a> <ul class="subs"><li>= <a href="#v:DefaultCompression">DefaultCompression</a> </li><li>| <a href="#v:NoCompression">NoCompression</a> </li><li>| <a href="#v:BestSpeed">BestSpeed</a> </li><li>| <a href="#v:BestCompression">BestCompression</a> </li><li>| <a href="#v:CompressionLevel">CompressionLevel</a> <a href="/usr/share/doc/ghc/html/libraries/base-4.3.1.0/Data-Int.html#t:Int">Int</a> </li></ul></li><li class="src short"><a href="#v:defaultCompression">defaultCompression</a> :: <a href="Codec-Compression-Zlib-Raw.html#t:CompressionLevel">CompressionLevel</a></li><li class="src short"><a href="#v:noCompression">noCompression</a> :: <a href="Codec-Compression-Zlib-Raw.html#t:CompressionLevel">CompressionLevel</a></li><li class="src short"><a href="#v:bestSpeed">bestSpeed</a> :: <a href="Codec-Compression-Zlib-Raw.html#t:CompressionLevel">CompressionLevel</a></li><li class="src short"><a href="#v:bestCompression">bestCompression</a> :: <a href="Codec-Compression-Zlib-Raw.html#t:CompressionLevel">CompressionLevel</a></li><li class="src short"><a href="#v:compressionLevel">compressionLevel</a> :: <a href="/usr/share/doc/ghc/html/libraries/base-4.3.1.0/Data-Int.html#t:Int">Int</a> -> <a href="Codec-Compression-Zlib-Raw.html#t:CompressionLevel">CompressionLevel</a></li><li class="src short"><span class="keyword">data</span> <a href="#t:Method">Method</a> = <a href="#v:Deflated">Deflated</a></li><li class="src short"><a href="#v:deflateMethod">deflateMethod</a> :: <a href="Codec-Compression-Zlib-Raw.html#t:Method">Method</a></li><li class="src short"><span class="keyword">data</span> <a href="#t:WindowBits">WindowBits</a> <ul class="subs"><li>= <a href="#v:WindowBits">WindowBits</a> <a href="/usr/share/doc/ghc/html/libraries/base-4.3.1.0/Data-Int.html#t:Int">Int</a> </li><li>| <a href="#v:DefaultWindowBits">DefaultWindowBits</a> </li></ul></li><li class="src short"><a href="#v:defaultWindowBits">defaultWindowBits</a> :: <a href="Codec-Compression-Zlib-Raw.html#t:WindowBits">WindowBits</a></li><li class="src short"><a href="#v:windowBits">windowBits</a> :: <a href="/usr/share/doc/ghc/html/libraries/base-4.3.1.0/Data-Int.html#t:Int">Int</a> -> <a href="Codec-Compression-Zlib-Raw.html#t:WindowBits">WindowBits</a></li><li class="src short"><span class="keyword">data</span> <a href="#t:MemoryLevel">MemoryLevel</a> <ul class="subs"><li>= <a href="#v:DefaultMemoryLevel">DefaultMemoryLevel</a> </li><li>| <a href="#v:MinMemoryLevel">MinMemoryLevel</a> </li><li>| <a href="#v:MaxMemoryLevel">MaxMemoryLevel</a> </li><li>| <a href="#v:MemoryLevel">MemoryLevel</a> <a href="/usr/share/doc/ghc/html/libraries/base-4.3.1.0/Data-Int.html#t:Int">Int</a> </li></ul></li><li class="src short"><a href="#v:defaultMemoryLevel">defaultMemoryLevel</a> :: <a href="Codec-Compression-Zlib-Raw.html#t:MemoryLevel">MemoryLevel</a></li><li class="src short"><a href="#v:minMemoryLevel">minMemoryLevel</a> :: <a href="Codec-Compression-Zlib-Raw.html#t:MemoryLevel">MemoryLevel</a></li><li class="src short"><a href="#v:maxMemoryLevel">maxMemoryLevel</a> :: <a href="Codec-Compression-Zlib-Raw.html#t:MemoryLevel">MemoryLevel</a></li><li class="src short"><a href="#v:memoryLevel">memoryLevel</a> :: <a href="/usr/share/doc/ghc/html/libraries/base-4.3.1.0/Data-Int.html#t:Int">Int</a> -> <a href="Codec-Compression-Zlib-Raw.html#t:MemoryLevel">MemoryLevel</a></li><li class="src short"><span class="keyword">data</span> <a href="#t:CompressionStrategy">CompressionStrategy</a> <ul class="subs"><li>= <a href="#v:DefaultStrategy">DefaultStrategy</a> </li><li>| <a href="#v:Filtered">Filtered</a> </li><li>| <a href="#v:HuffmanOnly">HuffmanOnly</a> </li></ul></li><li class="src short"><a href="#v:defaultStrategy">defaultStrategy</a> :: <a href="Codec-Compression-Zlib-Raw.html#t:CompressionStrategy">CompressionStrategy</a></li><li class="src short"><a href="#v:filteredStrategy">filteredStrategy</a> :: <a href="Codec-Compression-Zlib-Raw.html#t:CompressionStrategy">CompressionStrategy</a></li><li class="src short"><a href="#v:huffmanOnlyStrategy">huffmanOnlyStrategy</a> :: <a href="Codec-Compression-Zlib-Raw.html#t:CompressionStrategy">CompressionStrategy</a></li></ul></div><div id="interface"><h1 id="g:1">Simple compression and decompression </h1><div class="top"><p class="src"><a name="v:compress" class="def">compress</a> :: <a href="/usr/share/doc/ghc/html/libraries/bytestring-0.9.1.10/Data-ByteString-Lazy.html#t:ByteString">ByteString</a> -> <a href="/usr/share/doc/ghc/html/libraries/bytestring-0.9.1.10/Data-ByteString-Lazy.html#t:ByteString">ByteString</a><a href="src/Codec-Compression-Zlib-Raw.html#compress" class="link">Source</a></p></div><div class="top"><p class="src"><a name="v:decompress" class="def">decompress</a> :: <a href="/usr/share/doc/ghc/html/libraries/bytestring-0.9.1.10/Data-ByteString-Lazy.html#t:ByteString">ByteString</a> -> <a href="/usr/share/doc/ghc/html/libraries/bytestring-0.9.1.10/Data-ByteString-Lazy.html#t:ByteString">ByteString</a><a href="src/Codec-Compression-Zlib-Raw.html#decompress" class="link">Source</a></p></div><h1 id="g:2">Extended api with control over compression parameters </h1><div class="top"><p class="src"><a name="v:compressWith" class="def">compressWith</a> :: <a href="Codec-Compression-Zlib-Raw.html#t:CompressParams">CompressParams</a> -> <a href="/usr/share/doc/ghc/html/libraries/bytestring-0.9.1.10/Data-ByteString-Lazy.html#t:ByteString">ByteString</a> -> <a href="/usr/share/doc/ghc/html/libraries/bytestring-0.9.1.10/Data-ByteString-Lazy.html#t:ByteString">ByteString</a><a href="src/Codec-Compression-Zlib-Raw.html#compressWith" class="link">Source</a></p></div><div class="top"><p class="src"><a name="v:decompressWith" class="def">decompressWith</a> :: <a href="Codec-Compression-Zlib-Raw.html#t:DecompressParams">DecompressParams</a> -> <a href="/usr/share/doc/ghc/html/libraries/bytestring-0.9.1.10/Data-ByteString-Lazy.html#t:ByteString">ByteString</a> -> <a href="/usr/share/doc/ghc/html/libraries/bytestring-0.9.1.10/Data-ByteString-Lazy.html#t:ByteString">ByteString</a><a href="src/Codec-Compression-Zlib-Raw.html#decompressWith" class="link">Source</a></p></div><div class="top"><p class="src"><span class="keyword">data</span> <a name="t:CompressParams" class="def">CompressParams</a> <a href="src/Codec-Compression-Zlib-Internal.html#CompressParams" class="link">Source</a></p><div class="doc"><p>The full set of parameters for compression. The defaults are <code><a href="Codec-Compression-Zlib-Raw.html#v:defaultCompressParams">defaultCompressParams</a></code>. </p><p>The <code><a href="Codec-Compression-Zlib-Raw.html#v:compressBufferSize">compressBufferSize</a></code> 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 <code>16k</code>. If your extimate is wrong it does not matter too much, the default buffer size will be used for the remaining chunks. </p></div><div class="subs constructors"><p class="caption">Constructors</p><table><tr><td class="src"><a name="v:CompressParams" class="def">CompressParams</a></td><td class="doc empty"> </td></tr><tr><td colspan="2"><div class="subs fields"><p class="caption">Fields</p><dl><dt class="src"><a name="v:compressLevel" class="def">compressLevel</a> :: !<a href="Codec-Compression-Zlib-Raw.html#t:CompressionLevel">CompressionLevel</a></dt><dd class="doc empty"> </dd><dt class="src"><a name="v:compressMethod" class="def">compressMethod</a> :: !<a href="Codec-Compression-Zlib-Raw.html#t:Method">Method</a></dt><dd class="doc empty"> </dd><dt class="src"><a name="v:compressWindowBits" class="def">compressWindowBits</a> :: !<a href="Codec-Compression-Zlib-Raw.html#t:WindowBits">WindowBits</a></dt><dd class="doc empty"> </dd><dt class="src"><a name="v:compressMemoryLevel" class="def">compressMemoryLevel</a> :: !<a href="Codec-Compression-Zlib-Raw.html#t:MemoryLevel">MemoryLevel</a></dt><dd class="doc empty"> </dd><dt class="src"><a name="v:compressStrategy" class="def">compressStrategy</a> :: !<a href="Codec-Compression-Zlib-Raw.html#t:CompressionStrategy">CompressionStrategy</a></dt><dd class="doc empty"> </dd><dt class="src"><a name="v:compressBufferSize" class="def">compressBufferSize</a> :: !<a href="/usr/share/doc/ghc/html/libraries/base-4.3.1.0/Data-Int.html#t:Int">Int</a></dt><dd class="doc empty"> </dd></dl><div class="clear"></div></div></td></tr></table></div></div><div class="top"><p class="src"><a name="v:defaultCompressParams" class="def">defaultCompressParams</a> :: <a href="Codec-Compression-Zlib-Raw.html#t:CompressParams">CompressParams</a><a href="src/Codec-Compression-Zlib-Internal.html#defaultCompressParams" class="link">Source</a></p><div class="doc"><p>The default set of parameters for compression. This is typically used with the <code>compressWith</code> function with specific parameters overridden. </p></div></div><div class="top"><p class="src"><span class="keyword">data</span> <a name="t:DecompressParams" class="def">DecompressParams</a> <a href="src/Codec-Compression-Zlib-Internal.html#DecompressParams" class="link">Source</a></p><div class="doc"><p>The full set of parameters for decompression. The defaults are <code><a href="Codec-Compression-Zlib-Raw.html#v:defaultDecompressParams">defaultDecompressParams</a></code>. </p><p>The <code><a href="Codec-Compression-Zlib-Raw.html#v:decompressBufferSize">decompressBufferSize</a></code> 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 <code>32k</code>. If your extimate is wrong it does not matter too much, the default buffer size will be used for the remaining chunks. </p><p>One particular use case for setting the <code><a href="Codec-Compression-Zlib-Raw.html#v:decompressBufferSize">decompressBufferSize</a></code> is if you know the exact size of the decompressed data and want to produce a strict <code>Data.ByteString.ByteString</code>. The compression and deccompression functions use lazy <code>Data.ByteString.Lazy.ByteString</code>s but if you set the <code><a href="Codec-Compression-Zlib-Raw.html#v:decompressBufferSize">decompressBufferSize</a></code> correctly then you can generate a lazy <code>Data.ByteString.Lazy.ByteString</code> with exactly one chunk, which can be converted to a strict <code>Data.ByteString.ByteString</code> in <code>O(1)</code> time using <code><code>Data.ByteString.concat</code> . <code>Data.ByteString.Lazy.toChunks</code></code>. </p></div><div class="subs constructors"><p class="caption">Constructors</p><table><tr><td class="src"><a name="v:DecompressParams" class="def">DecompressParams</a></td><td class="doc empty"> </td></tr><tr><td colspan="2"><div class="subs fields"><p class="caption">Fields</p><dl><dt class="src"><a name="v:decompressWindowBits" class="def">decompressWindowBits</a> :: !<a href="Codec-Compression-Zlib-Raw.html#t:WindowBits">WindowBits</a></dt><dd class="doc empty"> </dd><dt class="src"><a name="v:decompressBufferSize" class="def">decompressBufferSize</a> :: !<a href="/usr/share/doc/ghc/html/libraries/base-4.3.1.0/Data-Int.html#t:Int">Int</a></dt><dd class="doc empty"> </dd></dl><div class="clear"></div></div></td></tr></table></div></div><div class="top"><p class="src"><a name="v:defaultDecompressParams" class="def">defaultDecompressParams</a> :: <a href="Codec-Compression-Zlib-Raw.html#t:DecompressParams">DecompressParams</a><a href="src/Codec-Compression-Zlib-Internal.html#defaultDecompressParams" class="link">Source</a></p><div class="doc"><p>The default set of parameters for decompression. This is typically used with the <code>compressWith</code> function with specific parameters overridden. </p></div></div><h2 id="g:3">The compression parameter types </h2><div class="top"><p class="src"><span class="keyword">data</span> <a name="t:CompressionLevel" class="def">CompressionLevel</a> <a href="src/Codec-Compression-Zlib-Stream.html#CompressionLevel" class="link">Source</a></p><div class="doc"><p>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. </p></div><div class="subs constructors"><p class="caption">Constructors</p><table><tr><td class="src"><a name="v:DefaultCompression" class="def">DefaultCompression</a></td><td class="doc empty"> </td></tr><tr><td class="src"><a name="v:NoCompression" class="def">NoCompression</a></td><td class="doc empty"> </td></tr><tr><td class="src"><a name="v:BestSpeed" class="def">BestSpeed</a></td><td class="doc empty"> </td></tr><tr><td class="src"><a name="v:BestCompression" class="def">BestCompression</a></td><td class="doc empty"> </td></tr><tr><td class="src"><a name="v:CompressionLevel" class="def">CompressionLevel</a> <a href="/usr/share/doc/ghc/html/libraries/base-4.3.1.0/Data-Int.html#t:Int">Int</a></td><td class="doc empty"> </td></tr></table></div></div><div class="top"><p class="src"><a name="v:defaultCompression" class="def">defaultCompression</a> :: <a href="Codec-Compression-Zlib-Raw.html#t:CompressionLevel">CompressionLevel</a><a href="src/Codec-Compression-Zlib-Stream.html#defaultCompression" class="link">Source</a></p><div class="doc"><p>The default compression level is 6 (that is, biased towards higher compression at expense of speed). </p></div></div><div class="top"><p class="src"><a name="v:noCompression" class="def">noCompression</a> :: <a href="Codec-Compression-Zlib-Raw.html#t:CompressionLevel">CompressionLevel</a><a href="src/Codec-Compression-Zlib-Stream.html#noCompression" class="link">Source</a></p><div class="doc"><p>No compression, just a block copy. </p></div></div><div class="top"><p class="src"><a name="v:bestSpeed" class="def">bestSpeed</a> :: <a href="Codec-Compression-Zlib-Raw.html#t:CompressionLevel">CompressionLevel</a><a href="src/Codec-Compression-Zlib-Stream.html#bestSpeed" class="link">Source</a></p><div class="doc"><p>The fastest compression method (less compression) </p></div></div><div class="top"><p class="src"><a name="v:bestCompression" class="def">bestCompression</a> :: <a href="Codec-Compression-Zlib-Raw.html#t:CompressionLevel">CompressionLevel</a><a href="src/Codec-Compression-Zlib-Stream.html#bestCompression" class="link">Source</a></p><div class="doc"><p>The slowest compression method (best compression). </p></div></div><div class="top"><p class="src"><a name="v:compressionLevel" class="def">compressionLevel</a> :: <a href="/usr/share/doc/ghc/html/libraries/base-4.3.1.0/Data-Int.html#t:Int">Int</a> -> <a href="Codec-Compression-Zlib-Raw.html#t:CompressionLevel">CompressionLevel</a><a href="src/Codec-Compression-Zlib-Stream.html#compressionLevel" class="link">Source</a></p><div class="doc"><p>A specific compression level between 0 and 9. </p></div></div><div class="top"><p class="src"><span class="keyword">data</span> <a name="t:Method" class="def">Method</a> <a href="src/Codec-Compression-Zlib-Stream.html#Method" class="link">Source</a></p><div class="doc"><p>The compression method </p></div><div class="subs constructors"><p class="caption">Constructors</p><table><tr><td class="src"><a name="v:Deflated" class="def">Deflated</a></td><td class="doc empty"> </td></tr></table></div></div><div class="top"><p class="src"><a name="v:deflateMethod" class="def">deflateMethod</a> :: <a href="Codec-Compression-Zlib-Raw.html#t:Method">Method</a><a href="src/Codec-Compression-Zlib-Stream.html#deflateMethod" class="link">Source</a></p><div class="doc"><p>'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. </p></div></div><div class="top"><p class="src"><span class="keyword">data</span> <a name="t:WindowBits" class="def">WindowBits</a> <a href="src/Codec-Compression-Zlib-Stream.html#WindowBits" class="link">Source</a></p><div class="doc"><p>This specifies the size of the compression window. Larger values of this parameter result in better compression at the expense of higher memory usage. </p><p>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 <code>8..15</code> which corresponds to compression window sizes of 256b to 32Kb. The default is 15 which is also the maximum size. </p><p>The total amount of memory used depends on the window bits and the <code><a href="Codec-Compression-Zlib-Raw.html#t:MemoryLevel">MemoryLevel</a></code>. See the <code><a href="Codec-Compression-Zlib-Raw.html#t:MemoryLevel">MemoryLevel</a></code> for the details. </p></div><div class="subs constructors"><p class="caption">Constructors</p><table><tr><td class="src"><a name="v:WindowBits" class="def">WindowBits</a> <a href="/usr/share/doc/ghc/html/libraries/base-4.3.1.0/Data-Int.html#t:Int">Int</a></td><td class="doc empty"> </td></tr><tr><td class="src"><a name="v:DefaultWindowBits" class="def">DefaultWindowBits</a></td><td class="doc empty"> </td></tr></table></div></div><div class="top"><p class="src"><a name="v:defaultWindowBits" class="def">defaultWindowBits</a> :: <a href="Codec-Compression-Zlib-Raw.html#t:WindowBits">WindowBits</a><a href="src/Codec-Compression-Zlib-Stream.html#defaultWindowBits" class="link">Source</a></p><div class="doc"><p>The default <code><a href="Codec-Compression-Zlib-Raw.html#t:WindowBits">WindowBits</a></code> is 15 which is also the maximum size. </p></div></div><div class="top"><p class="src"><a name="v:windowBits" class="def">windowBits</a> :: <a href="/usr/share/doc/ghc/html/libraries/base-4.3.1.0/Data-Int.html#t:Int">Int</a> -> <a href="Codec-Compression-Zlib-Raw.html#t:WindowBits">WindowBits</a><a href="src/Codec-Compression-Zlib-Stream.html#windowBits" class="link">Source</a></p><div class="doc"><p>A specific compression window size, specified in bits in the range <code>8..15</code> </p></div></div><div class="top"><p class="src"><span class="keyword">data</span> <a name="t:MemoryLevel" class="def">MemoryLevel</a> <a href="src/Codec-Compression-Zlib-Stream.html#MemoryLevel" class="link">Source</a></p><div class="doc"><p>The <code><a href="Codec-Compression-Zlib-Raw.html#t:MemoryLevel">MemoryLevel</a></code> 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. </p><p>The total amount of memory used for compression depends on the <code><a href="Codec-Compression-Zlib-Raw.html#t:WindowBits">WindowBits</a></code> and the <code><a href="Codec-Compression-Zlib-Raw.html#t:MemoryLevel">MemoryLevel</a></code>. For decompression it depends only on the <code><a href="Codec-Compression-Zlib-Raw.html#t:WindowBits">WindowBits</a></code>. The totals are given by the functions: </p><pre> compressTotal windowBits memLevel = 4 * 2^windowBits + 512 * 2^memLevel decompressTotal windowBits = 2^windowBits </pre><p>For example, for compression with the default <code>windowBits = 15</code> and <code>memLevel = 8</code> uses <code>256Kb</code>. So for example a network server with 100 concurrent compressed streams would use <code>25Mb</code>. The memory per stream can be halved (at the cost of somewhat degraded and slower compressionby) by reducing the <code>windowBits</code> and <code>memLevel</code> by one. </p><p>Decompression takes less memory, the default <code>windowBits = 15</code> corresponds to just <code>32Kb</code>. </p></div><div class="subs constructors"><p class="caption">Constructors</p><table><tr><td class="src"><a name="v:DefaultMemoryLevel" class="def">DefaultMemoryLevel</a></td><td class="doc empty"> </td></tr><tr><td class="src"><a name="v:MinMemoryLevel" class="def">MinMemoryLevel</a></td><td class="doc empty"> </td></tr><tr><td class="src"><a name="v:MaxMemoryLevel" class="def">MaxMemoryLevel</a></td><td class="doc empty"> </td></tr><tr><td class="src"><a name="v:MemoryLevel" class="def">MemoryLevel</a> <a href="/usr/share/doc/ghc/html/libraries/base-4.3.1.0/Data-Int.html#t:Int">Int</a></td><td class="doc empty"> </td></tr></table></div></div><div class="top"><p class="src"><a name="v:defaultMemoryLevel" class="def">defaultMemoryLevel</a> :: <a href="Codec-Compression-Zlib-Raw.html#t:MemoryLevel">MemoryLevel</a><a href="src/Codec-Compression-Zlib-Stream.html#defaultMemoryLevel" class="link">Source</a></p><div class="doc"><p>The default memory level. (Equivalent to <code><code><a href="Codec-Compression-Zlib-Raw.html#v:memoryLevel">memoryLevel</a></code> 8</code>) </p></div></div><div class="top"><p class="src"><a name="v:minMemoryLevel" class="def">minMemoryLevel</a> :: <a href="Codec-Compression-Zlib-Raw.html#t:MemoryLevel">MemoryLevel</a><a href="src/Codec-Compression-Zlib-Stream.html#minMemoryLevel" class="link">Source</a></p><div class="doc"><p>Use minimum memory. This is slow and reduces the compression ratio. (Equivalent to <code><code><a href="Codec-Compression-Zlib-Raw.html#v:memoryLevel">memoryLevel</a></code> 1</code>) </p></div></div><div class="top"><p class="src"><a name="v:maxMemoryLevel" class="def">maxMemoryLevel</a> :: <a href="Codec-Compression-Zlib-Raw.html#t:MemoryLevel">MemoryLevel</a><a href="src/Codec-Compression-Zlib-Stream.html#maxMemoryLevel" class="link">Source</a></p><div class="doc"><p>Use maximum memory for optimal compression speed. (Equivalent to <code><code><a href="Codec-Compression-Zlib-Raw.html#v:memoryLevel">memoryLevel</a></code> 9</code>) </p></div></div><div class="top"><p class="src"><a name="v:memoryLevel" class="def">memoryLevel</a> :: <a href="/usr/share/doc/ghc/html/libraries/base-4.3.1.0/Data-Int.html#t:Int">Int</a> -> <a href="Codec-Compression-Zlib-Raw.html#t:MemoryLevel">MemoryLevel</a><a href="src/Codec-Compression-Zlib-Stream.html#memoryLevel" class="link">Source</a></p><div class="doc"><p>A specific level in the range <code>1..9</code> </p></div></div><div class="top"><p class="src"><span class="keyword">data</span> <a name="t:CompressionStrategy" class="def">CompressionStrategy</a> <a href="src/Codec-Compression-Zlib-Stream.html#CompressionStrategy" class="link">Source</a></p><div class="doc"><p>The strategy parameter is used to tune the compression algorithm. </p><p>The strategy parameter only affects the compression ratio but not the correctness of the compressed output even if it is not set appropriately. </p></div><div class="subs constructors"><p class="caption">Constructors</p><table><tr><td class="src"><a name="v:DefaultStrategy" class="def">DefaultStrategy</a></td><td class="doc empty"> </td></tr><tr><td class="src"><a name="v:Filtered" class="def">Filtered</a></td><td class="doc empty"> </td></tr><tr><td class="src"><a name="v:HuffmanOnly" class="def">HuffmanOnly</a></td><td class="doc empty"> </td></tr></table></div></div><div class="top"><p class="src"><a name="v:defaultStrategy" class="def">defaultStrategy</a> :: <a href="Codec-Compression-Zlib-Raw.html#t:CompressionStrategy">CompressionStrategy</a><a href="src/Codec-Compression-Zlib-Stream.html#defaultStrategy" class="link">Source</a></p><div class="doc"><p>Use this default compression strategy for normal data. </p></div></div><div class="top"><p class="src"><a name="v:filteredStrategy" class="def">filteredStrategy</a> :: <a href="Codec-Compression-Zlib-Raw.html#t:CompressionStrategy">CompressionStrategy</a><a href="src/Codec-Compression-Zlib-Stream.html#filteredStrategy" class="link">Source</a></p><div class="doc"><p>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 <code>defaultCompressionStrategy</code> and <code>huffmanOnlyCompressionStrategy</code>. </p></div></div><div class="top"><p class="src"><a name="v:huffmanOnlyStrategy" class="def">huffmanOnlyStrategy</a> :: <a href="Codec-Compression-Zlib-Raw.html#t:CompressionStrategy">CompressionStrategy</a><a href="src/Codec-Compression-Zlib-Stream.html#huffmanOnlyStrategy" class="link">Source</a></p><div class="doc"><p>Use the Huffman-only compression strategy to force Huffman encoding only (no string match). </p></div></div></div></div><div id="footer"><p>Produced by <a href="http://www.haskell.org/haddock/">Haddock</a> version 2.9.2</p></div></body></html>