-- Hoogle documentation, generated by Haddock -- See Hoogle, http://www.haskell.org/hoogle/ -- | Compression and decompression in the gzip and zlib formats -- -- This package provides a pure interface for compressing and -- decompressing streams of data represented as lazy ByteStrings. -- It uses the zlib C library so it has high performance. It supports the -- "zlib", "gzip" and "raw" compression formats. -- -- It provides a convenient high level API suitable for most tasks and -- for the few cases where more control is needed it provides access to -- the full zlib feature set. @package zlib @version 0.5.3.1 -- | Pure stream based interface to lower level zlib wrapper module Codec.Compression.Zlib.Internal -- | Compress a data stream. -- -- There are no expected error conditions. All input data streams are -- valid. It is possible for unexpected errors to occur, such as running -- out of memory, or finding the wrong version of the zlib C library, -- these are thrown as exceptions. compress :: Format -> CompressParams -> ByteString -> ByteString -- | 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. data CompressParams CompressParams :: !CompressionLevel -> !Method -> !WindowBits -> !MemoryLevel -> !CompressionStrategy -> !Int -> CompressParams compressLevel :: CompressParams -> !CompressionLevel compressMethod :: CompressParams -> !Method compressWindowBits :: CompressParams -> !WindowBits compressMemoryLevel :: CompressParams -> !MemoryLevel compressStrategy :: CompressParams -> !CompressionStrategy compressBufferSize :: CompressParams -> !Int -- | The default set of parameters for compression. This is typically used -- with the compressWith function with specific parameters -- overridden. defaultCompressParams :: CompressParams -- | Decompress a data stream. -- -- It will throw an exception if any error is encountered in the input -- data. If you need more control over error handling then use -- decompressWithErrors. decompress :: Format -> DecompressParams -> ByteString -> ByteString -- | 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. data DecompressParams DecompressParams :: !WindowBits -> !Int -> DecompressParams decompressWindowBits :: DecompressParams -> !WindowBits decompressBufferSize :: DecompressParams -> !Int -- | The default set of parameters for decompression. This is typically -- used with the compressWith function with specific parameters -- overridden. defaultDecompressParams :: DecompressParams -- | The format used for compression or decompression. There are three -- variations. data Format GZip :: Format Zlib :: Format Raw :: Format GZipOrZlib :: Format -- | The gzip format uses a header with a checksum and some optional -- meta-data about the compressed file. It is intended primarily for -- compressing individual files but is also sometimes used for network -- protocols such as HTTP. The format is described in detail in RFC #1952 -- http://www.ietf.org/rfc/rfc1952.txt gzipFormat :: Format -- | The zlib format uses a minimal header with a checksum but no other -- meta-data. It is especially designed for use in network protocols. The -- format is described in detail in RFC #1950 -- http://www.ietf.org/rfc/rfc1950.txt zlibFormat :: Format -- | The 'raw' format is just the compressed data stream without any -- additional header, meta-data or data-integrity checksum. The format is -- described in detail in RFC #1951 -- http://www.ietf.org/rfc/rfc1951.txt rawFormat :: Format -- | This is not a format as such. It enabled zlib or gzip decoding with -- automatic header detection. This only makes sense for decompression. gzipOrZlibFormat :: Format -- | 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. data CompressionLevel DefaultCompression :: CompressionLevel NoCompression :: CompressionLevel BestSpeed :: CompressionLevel BestCompression :: CompressionLevel CompressionLevel :: Int -> CompressionLevel -- | The default compression level is 6 (that is, biased towards higher -- compression at expense of speed). defaultCompression :: CompressionLevel -- | No compression, just a block copy. noCompression :: CompressionLevel -- | The fastest compression method (less compression) bestSpeed :: CompressionLevel -- | The slowest compression method (best compression). bestCompression :: CompressionLevel -- | A specific compression level between 0 and 9. compressionLevel :: Int -> CompressionLevel -- | The compression method data Method Deflated :: Method -- | '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. deflateMethod :: Method -- | 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 8..15 -- which corresponds to compression window sizes of 256b 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. data WindowBits WindowBits :: Int -> WindowBits DefaultWindowBits :: WindowBits -- | The default WindowBits is 15 which is also the maximum size. defaultWindowBits :: WindowBits -- | A specific compression window size, specified in bits in the range -- 8..15 windowBits :: Int -> WindowBits -- | 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. data MemoryLevel DefaultMemoryLevel :: MemoryLevel MinMemoryLevel :: MemoryLevel MaxMemoryLevel :: MemoryLevel MemoryLevel :: Int -> MemoryLevel -- | The default memory level. (Equivalent to memoryLevel -- 8) defaultMemoryLevel :: MemoryLevel -- | Use minimum memory. This is slow and reduces the compression ratio. -- (Equivalent to memoryLevel 1) minMemoryLevel :: MemoryLevel -- | Use maximum memory for optimal compression speed. (Equivalent to -- memoryLevel 9) maxMemoryLevel :: MemoryLevel -- | A specific level in the range 1..9 memoryLevel :: Int -> MemoryLevel -- | 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. data CompressionStrategy DefaultStrategy :: CompressionStrategy Filtered :: CompressionStrategy HuffmanOnly :: CompressionStrategy -- | Use this default compression strategy for normal data. defaultStrategy :: CompressionStrategy -- | 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. filteredStrategy :: CompressionStrategy -- | Use the Huffman-only compression strategy to force Huffman encoding -- only (no string match). huffmanOnlyStrategy :: CompressionStrategy -- | Like decompress but returns a DecompressStream data -- structure that contains an explicit representation of the error -- conditions that one may encounter when decompressing. -- -- Note that in addition to errors in the input data, it is possible for -- other unexpected errors to occur, such as out of memory, or finding -- the wrong version of the zlib C library, these are still thrown as -- exceptions (because representing them as data would make this function -- impure). decompressWithErrors :: Format -> DecompressParams -> ByteString -> DecompressStream -- | A sequence of chunks of data produced from decompression. -- -- The difference from a simple list is that it contains a representation -- of errors as data rather than as exceptions. This allows you to handle -- error conditions explicitly. data DecompressStream StreamEnd :: DecompressStream StreamChunk :: ByteString -> DecompressStream -> DecompressStream -- | An error code and a human readable error message. StreamError :: DecompressError -> String -> DecompressStream -- | The possible error cases when decompressing a stream. data DecompressError -- | The compressed data stream ended prematurely. This may happen if the -- input data stream was truncated. TruncatedInput :: DecompressError -- | It is possible to do zlib compression with a custom dictionary. This -- allows slightly higher compression ratios for short files. However -- such compressed streams require the same dictionary when -- decompressing. This zlib binding does not currently support custom -- dictionaries. This error is for when we encounter a compressed stream -- that needs a dictionary. DictionaryRequired :: DecompressError -- | If the compressed data stream is corrupted in any way then you will -- get this error, for example if the input data just isn't a compressed -- zlib data stream. In particular if the data checksum turns out to be -- wrong then you will get all the decompressed data but this error at -- the end, instead of the normal sucessful StreamEnd. DataError :: DecompressError -- | Fold an DecompressionStream. Just like foldr but with -- an extra error case. For example to convert to a list and translate -- the errors into exceptions: -- -- 
--   foldDecompressStream (:) [] (\code msg -> error msg)
--
foldDecompressStream :: (ByteString -> a -> a) -> a -> (DecompressError -> String -> a) -> DecompressStream -> a -- | Convert a DecompressStream to a lazy ByteString. If -- any decompression errors are encountered then they are thrown as -- exceptions. -- -- This is a special case of foldDecompressStream. fromDecompressStream :: DecompressStream -> ByteString -- | 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/ module Codec.Compression.Zlib.Raw compress :: ByteString -> ByteString decompress :: ByteString -> ByteString compressWith :: CompressParams -> ByteString -> ByteString decompressWith :: DecompressParams -> ByteString -> ByteString -- | 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. data CompressParams CompressParams :: !CompressionLevel -> !Method -> !WindowBits -> !MemoryLevel -> !CompressionStrategy -> !Int -> CompressParams compressLevel :: CompressParams -> !CompressionLevel compressMethod :: CompressParams -> !Method compressWindowBits :: CompressParams -> !WindowBits compressMemoryLevel :: CompressParams -> !MemoryLevel compressStrategy :: CompressParams -> !CompressionStrategy compressBufferSize :: CompressParams -> !Int -- | The default set of parameters for compression. This is typically used -- with the compressWith function with specific parameters -- overridden. defaultCompressParams :: CompressParams -- | 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. data DecompressParams DecompressParams :: !WindowBits -> !Int -> DecompressParams decompressWindowBits :: DecompressParams -> !WindowBits decompressBufferSize :: DecompressParams -> !Int -- | The default set of parameters for decompression. This is typically -- used with the compressWith function with specific parameters -- overridden. defaultDecompressParams :: DecompressParams -- | 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. data CompressionLevel DefaultCompression :: CompressionLevel NoCompression :: CompressionLevel BestSpeed :: CompressionLevel BestCompression :: CompressionLevel CompressionLevel :: Int -> CompressionLevel -- | The default compression level is 6 (that is, biased towards higher -- compression at expense of speed). defaultCompression :: CompressionLevel -- | No compression, just a block copy. noCompression :: CompressionLevel -- | The fastest compression method (less compression) bestSpeed :: CompressionLevel -- | The slowest compression method (best compression). bestCompression :: CompressionLevel -- | A specific compression level between 0 and 9. compressionLevel :: Int -> CompressionLevel -- | The compression method data Method Deflated :: Method -- | '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. deflateMethod :: Method -- | 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 8..15 -- which corresponds to compression window sizes of 256b 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. data WindowBits WindowBits :: Int -> WindowBits DefaultWindowBits :: WindowBits -- | The default WindowBits is 15 which is also the maximum size. defaultWindowBits :: WindowBits -- | A specific compression window size, specified in bits in the range -- 8..15 windowBits :: Int -> WindowBits -- | 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. data MemoryLevel DefaultMemoryLevel :: MemoryLevel MinMemoryLevel :: MemoryLevel MaxMemoryLevel :: MemoryLevel MemoryLevel :: Int -> MemoryLevel -- | The default memory level. (Equivalent to memoryLevel -- 8) defaultMemoryLevel :: MemoryLevel -- | Use minimum memory. This is slow and reduces the compression ratio. -- (Equivalent to memoryLevel 1) minMemoryLevel :: MemoryLevel -- | Use maximum memory for optimal compression speed. (Equivalent to -- memoryLevel 9) maxMemoryLevel :: MemoryLevel -- | A specific level in the range 1..9 memoryLevel :: Int -> MemoryLevel -- | 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. data CompressionStrategy DefaultStrategy :: CompressionStrategy Filtered :: CompressionStrategy HuffmanOnly :: CompressionStrategy -- | Use this default compression strategy for normal data. defaultStrategy :: CompressionStrategy -- | 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. filteredStrategy :: CompressionStrategy -- | Use the Huffman-only compression strategy to force Huffman encoding -- only (no string match). huffmanOnlyStrategy :: CompressionStrategy -- | 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 -- | 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 -- | 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: -- -- -- -- 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 -- | 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 -- | Like decompress but with the ability to specify various -- decompression parameters. Typical usage: -- -- 
--   decompressWith defaultCompressParams { ... }
--
decompressWith :: DecompressParams -> ByteString -> ByteString -- | 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. data CompressParams CompressParams :: !CompressionLevel -> !Method -> !WindowBits -> !MemoryLevel -> !CompressionStrategy -> !Int -> CompressParams compressLevel :: CompressParams -> !CompressionLevel compressMethod :: CompressParams -> !Method compressWindowBits :: CompressParams -> !WindowBits compressMemoryLevel :: CompressParams -> !MemoryLevel compressStrategy :: CompressParams -> !CompressionStrategy compressBufferSize :: CompressParams -> !Int -- | The default set of parameters for compression. This is typically used -- with the compressWith function with specific parameters -- overridden. defaultCompressParams :: CompressParams -- | 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. data DecompressParams DecompressParams :: !WindowBits -> !Int -> DecompressParams decompressWindowBits :: DecompressParams -> !WindowBits decompressBufferSize :: DecompressParams -> !Int -- | The default set of parameters for decompression. This is typically -- used with the compressWith function with specific parameters -- overridden. defaultDecompressParams :: DecompressParams -- | 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. data CompressionLevel DefaultCompression :: CompressionLevel NoCompression :: CompressionLevel BestSpeed :: CompressionLevel BestCompression :: CompressionLevel CompressionLevel :: Int -> CompressionLevel -- | The default compression level is 6 (that is, biased towards higher -- compression at expense of speed). defaultCompression :: CompressionLevel -- | No compression, just a block copy. noCompression :: CompressionLevel -- | The fastest compression method (less compression) bestSpeed :: CompressionLevel -- | The slowest compression method (best compression). bestCompression :: CompressionLevel -- | A specific compression level between 0 and 9. compressionLevel :: Int -> CompressionLevel -- | The compression method data Method Deflated :: Method -- | '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. deflateMethod :: Method -- | 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 8..15 -- which corresponds to compression window sizes of 256b 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. data WindowBits WindowBits :: Int -> WindowBits DefaultWindowBits :: WindowBits -- | The default WindowBits is 15 which is also the maximum size. defaultWindowBits :: WindowBits -- | A specific compression window size, specified in bits in the range -- 8..15 windowBits :: Int -> WindowBits -- | 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. data MemoryLevel DefaultMemoryLevel :: MemoryLevel MinMemoryLevel :: MemoryLevel MaxMemoryLevel :: MemoryLevel MemoryLevel :: Int -> MemoryLevel -- | The default memory level. (Equivalent to memoryLevel -- 8) defaultMemoryLevel :: MemoryLevel -- | Use minimum memory. This is slow and reduces the compression ratio. -- (Equivalent to memoryLevel 1) minMemoryLevel :: MemoryLevel -- | Use maximum memory for optimal compression speed. (Equivalent to -- memoryLevel 9) maxMemoryLevel :: MemoryLevel -- | A specific level in the range 1..9 memoryLevel :: Int -> MemoryLevel -- | 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. data CompressionStrategy DefaultStrategy :: CompressionStrategy Filtered :: CompressionStrategy HuffmanOnly :: CompressionStrategy -- | Use this default compression strategy for normal data. defaultStrategy :: CompressionStrategy -- | 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. filteredStrategy :: CompressionStrategy -- | Use the Huffman-only compression strategy to force Huffman encoding -- only (no string match). huffmanOnlyStrategy :: CompressionStrategy -- | Compression and decompression of data streams in the gzip format. -- -- The format is described in detail in RFC #1952: -- http://www.ietf.org/rfc/rfc1952.txt -- -- See also the zlib home page: http://zlib.net/ module Codec.Compression.GZip -- | Compress a stream of data into the gzip 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 -- | Decompress a stream of data in the gzip format. -- -- There are a number of errors that can occur. In each case an exception -- will be thrown. The possible error conditions are: -- -- -- -- 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 -- | 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 -- | Like decompress but with the ability to specify various -- decompression parameters. Typical usage: -- -- 
--   decompressWith defaultCompressParams { ... }
--
decompressWith :: DecompressParams -> ByteString -> ByteString -- | 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. data CompressParams CompressParams :: !CompressionLevel -> !Method -> !WindowBits -> !MemoryLevel -> !CompressionStrategy -> !Int -> CompressParams compressLevel :: CompressParams -> !CompressionLevel compressMethod :: CompressParams -> !Method compressWindowBits :: CompressParams -> !WindowBits compressMemoryLevel :: CompressParams -> !MemoryLevel compressStrategy :: CompressParams -> !CompressionStrategy compressBufferSize :: CompressParams -> !Int -- | The default set of parameters for compression. This is typically used -- with the compressWith function with specific parameters -- overridden. defaultCompressParams :: CompressParams -- | 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. data DecompressParams DecompressParams :: !WindowBits -> !Int -> DecompressParams decompressWindowBits :: DecompressParams -> !WindowBits decompressBufferSize :: DecompressParams -> !Int -- | The default set of parameters for decompression. This is typically -- used with the compressWith function with specific parameters -- overridden. defaultDecompressParams :: DecompressParams -- | 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. data CompressionLevel DefaultCompression :: CompressionLevel NoCompression :: CompressionLevel BestSpeed :: CompressionLevel BestCompression :: CompressionLevel CompressionLevel :: Int -> CompressionLevel -- | The default compression level is 6 (that is, biased towards higher -- compression at expense of speed). defaultCompression :: CompressionLevel -- | No compression, just a block copy. noCompression :: CompressionLevel -- | The fastest compression method (less compression) bestSpeed :: CompressionLevel -- | The slowest compression method (best compression). bestCompression :: CompressionLevel -- | A specific compression level between 0 and 9. compressionLevel :: Int -> CompressionLevel -- | The compression method data Method Deflated :: Method -- | '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. deflateMethod :: Method -- | 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 8..15 -- which corresponds to compression window sizes of 256b 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. data WindowBits WindowBits :: Int -> WindowBits DefaultWindowBits :: WindowBits -- | The default WindowBits is 15 which is also the maximum size. defaultWindowBits :: WindowBits -- | A specific compression window size, specified in bits in the range -- 8..15 windowBits :: Int -> WindowBits -- | 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. data MemoryLevel DefaultMemoryLevel :: MemoryLevel MinMemoryLevel :: MemoryLevel MaxMemoryLevel :: MemoryLevel MemoryLevel :: Int -> MemoryLevel -- | The default memory level. (Equivalent to memoryLevel -- 8) defaultMemoryLevel :: MemoryLevel -- | Use minimum memory. This is slow and reduces the compression ratio. -- (Equivalent to memoryLevel 1) minMemoryLevel :: MemoryLevel -- | Use maximum memory for optimal compression speed. (Equivalent to -- memoryLevel 9) maxMemoryLevel :: MemoryLevel -- | A specific level in the range 1..9 memoryLevel :: Int -> MemoryLevel -- | 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. data CompressionStrategy DefaultStrategy :: CompressionStrategy Filtered :: CompressionStrategy HuffmanOnly :: CompressionStrategy -- | Use this default compression strategy for normal data. defaultStrategy :: CompressionStrategy -- | 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. filteredStrategy :: CompressionStrategy -- | Use the Huffman-only compression strategy to force Huffman encoding -- only (no string match). huffmanOnlyStrategy :: CompressionStrategy