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Diffstat (limited to 'erts/doc/src/zlib.xml')
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1 files changed, 392 insertions, 301 deletions
diff --git a/erts/doc/src/zlib.xml b/erts/doc/src/zlib.xml index 0a641346d9..f8140544b7 100644 --- a/erts/doc/src/zlib.xml +++ b/erts/doc/src/zlib.xml @@ -4,7 +4,7 @@ <erlref> <header> <copyright> - <year>2005</year><year>2013</year> + <year>2005</year><year>2017</year> <holder>Ericsson AB. All Rights Reserved.</holder> </copyright> <legalnotice> @@ -30,13 +30,18 @@ <file>zlib.xml</file> </header> <module>zlib</module> - <modulesummary>Zlib Compression interface.</modulesummary> + <modulesummary>zlib compression interface.</modulesummary> <description> - <p>The zlib module provides an API for the zlib library - (http://www.zlib.org). - It is used to compress and decompress data. The - data format is described by RFCs 1950 to 1952.</p> - <p>A typical (compress) usage looks like:</p> + <p>This module provides an API for the zlib library + (<url href="http://www.zlib.net">www.zlib.net</url>). + It is used to compress and decompress data. + The data format is described by + <url href="https://www.ietf.org/rfc/rfc1950.txt">RFC 1950</url>, + <url href="https://www.ietf.org/rfc/rfc1951.txt">RFC 1951</url>, and + <url href="https://www.ietf.org/rfc/rfc1952.txt">RFC 1952</url>.</p> + + <p>A typical (compress) usage is as follows:</p> + <pre> Z = zlib:open(), ok = zlib:deflateInit(Z,default), @@ -50,29 +55,25 @@ Last = zlib:deflate(Z, [], finish), ok = zlib:deflateEnd(Z), zlib:close(Z), list_to_binary([Compressed|Last])</pre> + <p>In all functions errors, <c>{'EXIT',{Reason,Backtrace}}</c>, - might be thrown, where <c>Reason</c> describes the - error. Typical reasons are:</p> + can be thrown, where <c>Reason</c> describes the error.</p> + + <p>Typical <c>Reasons</c>s:</p> + <taglist> <tag><c>badarg</c></tag> - <item> - <p>Bad argument</p> + <item>Bad argument. </item> <tag><c>data_error</c></tag> - <item> - <p>The data contains errors</p> + <item>The data contains errors. </item> <tag><c>stream_error</c></tag> - <item> - <p>Inconsistent stream state</p> - </item> + <item>Inconsistent stream state.</item> <tag><c>einval</c></tag> - <item> - <p>Bad value or wrong function called</p> - </item> + <item>Bad value or wrong function called.</item> <tag><c>{need_dictionary,Adler32}</c></tag> - <item> - <p>See <c>inflate/2</c></p> + <item>See <seealso marker="#inflate/2"><c>inflate/2</c></seealso>. </item> </taglist> </description> @@ -81,7 +82,7 @@ list_to_binary([Compressed|Last])</pre> <datatype> <name name="zstream"/> <desc> - <p>A zlib stream, see <seealso marker="#open/0">open/0</seealso>. + <p>A zlib stream, see <seealso marker="#open/0"><c>open/0</c></seealso>. </p> </desc> </datatype> @@ -104,116 +105,144 @@ list_to_binary([Compressed|Last])</pre> </desc> </datatype> </datatypes> + <funcs> <func> - <name name="open" arity="0"/> - <fsummary>Open a stream and return a stream reference</fsummary> + <name name="adler32" arity="2"/> + <fsummary>Calculate the Adler checksum.</fsummary> + <desc> + <p>Calculates the Adler-32 checksum for <c><anno>Data</anno></c>.</p> + </desc> + </func> + + <func> + <name name="adler32" arity="3"/> + <fsummary>Calculate the Adler checksum.</fsummary> + <desc> + <p>Updates a running Adler-32 checksum for <c><anno>Data</anno></c>. + If <c><anno>Data</anno></c> is the empty binary or the empty iolist, + this function returns the required initial value for the checksum.</p> + <p>Example:</p> + <pre> +Crc = lists:foldl(fun(Data,Crc0) -> + zlib:adler32(Z, Crc0, Data), + end, zlib:adler32(Z,<< >>), Datas)</pre> + </desc> + </func> + + <func> + <name name="adler32_combine" arity="4"/> + <fsummary>Combine two Adler-32 checksums.</fsummary> <desc> - <p>Open a zlib stream.</p> + <p>Combines two Adler-32 checksums into one. For two binaries or + iolists, <c>Data1</c> and <c>Data2</c> with sizes of <c>Size1</c> + and <c><anno>Size2</anno></c>, with Adler-32 checksums + <c><anno>Adler1</anno></c> and <c><anno>Adler2</anno></c>.</p> + <p>This function returns the <c><anno>Adler</anno></c> checksum of + <c>[Data1,Data2]</c>, requiring only <c><anno>Adler1</anno></c>, + <c><anno>Adler2</anno></c>, and <c><anno>Size2</anno></c>.</p> </desc> </func> + <func> <name name="close" arity="1"/> - <fsummary>Close a stream</fsummary> + <fsummary>Close a stream.</fsummary> <desc> <p>Closes the stream referenced by <c><anno>Z</anno></c>.</p> </desc> </func> + <func> - <name name="deflateInit" arity="1"/> - <fsummary>Initialize a session for compression</fsummary> + <name name="compress" arity="1"/> + <fsummary>Compress data with standard zlib functionality.</fsummary> <desc> - <p>Same as <c>zlib:deflateInit(<anno>Z</anno>, default)</c>.</p> + <p>Compresses data with zlib headers and checksum.</p> </desc> </func> + <func> - <name name="deflateInit" arity="2"/> - <fsummary>Initialize a session for compression</fsummary> + <name name="crc32" arity="1"/> + <fsummary>Get current CRC.</fsummary> <desc> - <p>Initialize a zlib stream for compression.</p> - <p><c><anno>Level</anno></c> decides the compression level to be used, 0 - (<c>none</c>), gives no compression at all, 1 - (<c>best_speed</c>) gives best speed and 9 - (<c>best_compression</c>) gives best compression.</p> + <p>Gets the current calculated CRC checksum.</p> </desc> </func> + <func> - <name name="deflateInit" arity="6"/> - <fsummary>Initialize a session for compression</fsummary> + <name name="crc32" arity="2"/> + <fsummary>Calculate CRC.</fsummary> <desc> - <p>Initiates a zlib stream for compression.</p> - <p>The <c><anno>Level</anno></c> parameter decides the compression level to be - used, 0 (<c>none</c>), gives no compression at all, 1 - (<c>best_speed</c>) gives best speed and 9 - (<c>best_compression</c>) gives best compression.</p> - <p>The <c><anno>Method</anno></c> parameter decides which compression method to use, - currently the only supported method is <c>deflated</c>.</p> - <p>The <c><anno>WindowBits</anno></c> parameter is the base two logarithm - of the window size (the size of the history buffer). It - should be in the range 8 through 15. Larger values - of this parameter result in better compression at the - expense of memory usage. The default value is 15 if - <c>deflateInit/2</c>. A negative <c><anno>WindowBits</anno></c> - value suppresses the zlib header (and checksum) from the - stream. Note that the zlib source mentions this only as a - undocumented feature.</p> - <p>The <c><anno>MemLevel</anno></c> parameter specifies how much memory - should be allocated for the internal compression - state. <c><anno>MemLevel</anno></c>=1 uses minimum memory but is slow and - reduces compression ratio; <c><anno>MemLevel</anno></c>=9 uses maximum - memory for optimal speed. The default value is 8.</p> - <p>The <c><anno>Strategy</anno></c> parameter is used to tune - the compression algorithm. Use the value <c>default</c> for - normal data, <c>filtered</c> for data produced by a filter (or - predictor), <c>huffman_only</c> to force Huffman encoding - only (no string match), or <c>rle</c> to limit match - distances to one (run-length encoding). 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 <c>filtered</c>is to - force more Huffman coding and less string matching; it is - somewhat intermediate between <c>default</c> and - <c>huffman_only</c>. <c>rle</c> is designed to be almost as - fast as <c>huffman_only</c>, but give better compression for PNG - image data. The <c><anno>Strategy</anno></c> parameter only - affects the compression ratio but not the correctness of the - compressed output even if it is not set appropriately.</p> + <p>Calculates the CRC checksum for <c><anno>Data</anno></c>.</p> + </desc> + </func> + + <func> + <name name="crc32" arity="3"/> + <fsummary>Calculate CRC.</fsummary> + <desc> + <p>Updates a running CRC checksum for <c><anno>Data</anno></c>. + If <c><anno>Data</anno></c> is the empty binary or the empty iolist, + this function returns the required initial value for the CRC.</p> + <p>Example:</p> + <pre> +Crc = lists:foldl(fun(Data,Crc0) -> + zlib:crc32(Z, Crc0, Data), + end, zlib:crc32(Z,<< >>), Datas)</pre> + </desc> + </func> + + <func> + <name name="crc32_combine" arity="4"/> + <fsummary>Combine two CRCs.</fsummary> + <desc> + <p>Combines two CRC checksums into one. For two binaries or iolists, + <c>Data1</c> and <c>Data2</c> with sizes of <c>Size1</c> and + <c><anno>Size2</anno></c>, with CRC checksums <c><anno>CRC1</anno></c> + and <c><anno>CRC2</anno></c>.</p> + <p>This function returns the <c><anno>CRC</anno></c> checksum of + <c>[Data1,Data2]</c>, requiring only <c><anno>CRC1</anno></c>, + <c><anno>CRC2</anno></c>, and <c><anno>Size2</anno></c>.</p> </desc> </func> + <func> <name name="deflate" arity="2"/> - <fsummary>Compress data</fsummary> + <fsummary>Compress data.</fsummary> <desc> <p>Same as <c>deflate(<anno>Z</anno>, <anno>Data</anno>, none)</c>.</p> </desc> </func> + <func> <name name="deflate" arity="3"/> - <fsummary>Compress data</fsummary> + <fsummary>Compress data.</fsummary> <desc> - <p><c>deflate/3</c> compresses as much data as possible, and - stops when the input buffer becomes empty. It may introduce + <p>Compresses as much data as possible, and + stops when the input buffer becomes empty. It can introduce some output latency (reading input without producing any output) except when forced to flush.</p> - <p>If the parameter <c><anno>Flush</anno></c> is set to <c>sync</c>, all + <p>If <c><anno>Flush</anno></c> is set to <c>sync</c>, all pending output is flushed to the output buffer and the output is aligned on a byte boundary, so that the decompressor can get all input data available so far. - Flushing may degrade compression for some compression algorithms and so - it should be used only when necessary.</p> - <p>If <c><anno>Flush</anno></c> is set to <c>full</c>, all output is flushed as with - <c>sync</c>, and the compression state is reset so that decompression can - restart from this point if previous compressed data has been damaged or if - random access is desired. Using <c>full</c> too often can seriously degrade - the compression.</p> - <p>If the parameter <c><anno>Flush</anno></c> is set to <c>finish</c>, - pending input is processed, pending output is flushed and - <c>deflate/3</c> returns. Afterwards the only possible - operations on the stream are <c>deflateReset/1</c> or <c>deflateEnd/1</c>.</p> - <p><c><anno>Flush</anno></c> can be set to <c>finish</c> immediately after - <c>deflateInit</c> if all compression is to be done in one step.</p> + Flushing can degrade compression for some compression algorithms; + thus, use it only when necessary.</p> + <p>If <c><anno>Flush</anno></c> is set to <c>full</c>, all output is + flushed as with <c>sync</c>, and the compression state is reset so + that decompression can restart from this point if previous compressed + data has been damaged or if random access is desired. Using + <c>full</c> too often can seriously degrade the compression.</p> + <p>If <c><anno>Flush</anno></c> is set to <c>finish</c>, + pending input is processed, pending output is flushed, and + <c>deflate/3</c> returns. Afterwards the only possible operations + on the stream are + <seealso marker="#deflateReset/1"><c>deflateReset/1</c></seealso> or + <seealso marker="#deflateEnd/1"><c>deflateEnd/1</c></seealso>.</p> + <p><c><anno>Flush</anno></c> can be set to <c>finish</c> immediately + after <seealso marker="#deflateInit/1"><c>deflateInit</c></seealso> + if all compression is to be done in one step.</p> + <p>Example:</p> <pre> - zlib:deflateInit(Z), B1 = zlib:deflate(Z,Data), B2 = zlib:deflate(Z,<< >>,finish), @@ -221,116 +250,243 @@ zlib:deflateEnd(Z), list_to_binary([B1,B2])</pre> </desc> </func> + <func> - <name name="deflateSetDictionary" arity="2"/> - <fsummary>Initialize the compression dictionary</fsummary> + <name name="deflateEnd" arity="1"/> + <fsummary>End deflate session.</fsummary> <desc> - <p>Initializes the compression dictionary from the given byte - sequence without producing any compressed output. This - function must be called immediately after - <c>deflateInit/[1|2|6]</c> or <c>deflateReset/1</c>, before - any call of <c>deflate/3</c>. The compressor and - decompressor must use exactly the same dictionary (see - <c>inflateSetDictionary/2</c>). The adler checksum of the - dictionary is returned.</p> + <p>Ends the deflate session and cleans all data used. Notice that this + function throws a <c>data_error</c> exception if the last call to + <seealso marker="#deflate/3"><c>deflate/3</c></seealso> + was not called with <c>Flush</c> set to <c>finish</c>.</p> </desc> </func> + <func> - <name name="deflateReset" arity="1"/> - <fsummary>Reset the deflate session</fsummary> + <name name="deflateInit" arity="1"/> + <fsummary>Initialize a session for compression.</fsummary> <desc> - <p>This function is equivalent to <c>deflateEnd/1</c> - followed by <c>deflateInit/[1|2|6]</c>, but does not free - and reallocate all the internal compression state. The - stream will keep the same compression level and any other - attributes.</p> + <p>Same as <c>zlib:deflateInit(<anno>Z</anno>, default)</c>.</p> + </desc> + </func> + + <func> + <name name="deflateInit" arity="2"/> + <fsummary>Initialize a session for compression.</fsummary> + <desc> + <p>Initializes a zlib stream for compression.</p> + <p><c><anno>Level</anno></c> decides the compression level to be + used:</p> + <list type="bulleted"> + <item>0 (<c>none</c>), gives no compression</item> + <item>1 (<c>best_speed</c>) gives best speed</item> + <item>9 (<c>best_compression</c>) gives best compression</item> + </list> + </desc> + </func> + + <func> + <name name="deflateInit" arity="6"/> + <fsummary>Initialize a session for compression.</fsummary> + <desc> + <p>Initiates a zlib stream for compression.</p> + <taglist> + <tag><c><anno>Level</anno></c></tag> + <item> + <p>Compression level to use:</p> + <list type="bulleted"> + <item>0 (<c>none</c>), gives no compression</item> + <item>1 (<c>best_speed</c>) gives best speed</item> + <item>9 (<c>best_compression</c>) gives best compression</item> + </list> + </item> + <tag><c><anno>Method</anno></c></tag> + <item> + <p>Compression method to use, currently the only supported method + is <c>deflated</c>.</p> + </item> + <tag><c><anno>WindowBits</anno></c></tag> + <item> + <p>The base two logarithm of the window size (the size of the + history buffer). It is to be in the range 8 through 15. Larger + values result in better compression at the expense of memory + usage. Defaults to 15 if <seealso marker="#deflateInit/2"> + <c>deflateInit/2</c></seealso> is used. A negative + <c><anno>WindowBits</anno></c> value suppresses the zlib header + (and checksum) from the stream. Notice that the zlib source + mentions this only as a undocumented feature.</p> + <warning> + <p>Due to a known bug in the underlying zlib library, <c>WindowBits</c> values 8 and -8 + do not work as expected. In zlib versions before 1.2.9 values + 8 and -8 are automatically changed to 9 and -9. <em>From zlib version 1.2.9 + value -8 is rejected</em> causing <c>zlib:deflateInit/6</c> to fail + (8 is still changed to 9). It also seem possible that future versions + of zlib may fix this bug and start accepting 8 and -8 as is.</p> + <p>Conclusion: Avoid values 8 and -8 unless you know your zlib version supports them.</p> + </warning> + </item> + <tag><c><anno>MemLevel</anno></c></tag> + <item> + <p>Specifies how much memory is to be allocated for the internal + compression state: <c><anno>MemLevel</anno></c>=1 uses minimum + memory but is slow and reduces compression ratio; + <c><anno>MemLevel</anno></c>=9 uses maximum memory for optimal + speed. Defaults to 8.</p> + </item> + <tag><c><anno>Strategy</anno></c></tag> + <item> + <p>Tunes the compression algorithm. Use the following values:</p> + <list type="bulleted"> + <item><c>default</c> for normal data</item> + <item><c>filtered</c> for data produced by a filter (or + predictor)</item> + <item><c>huffman_only</c> to force Huffman encoding only + (no string match)</item> + <item><c>rle</c> to limit match distances to one (run-length + encoding)</item> + </list> + <p>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 <c>filtered</c> is to + force more Huffman coding and less string matching; it is somewhat + intermediate between <c>default</c> and <c>huffman_only</c>. + <c>rle</c> is designed to be almost as fast as + <c>huffman_only</c>, but gives better compression for PNG image + data.</p> + <p><c><anno>Strategy</anno></c> affects only the compression ratio, + but not the correctness of the compressed output even if it is not + set appropriately.</p> + </item> + </taglist> </desc> </func> + <func> <name name="deflateParams" arity="3"/> - <fsummary>Dynamicly update deflate parameters</fsummary> + <fsummary>Dynamicly update deflate parameters.</fsummary> <desc> - <p>Dynamically update the compression level and compression - strategy. The interpretation of <c><anno>Level</anno></c> and - <c><anno>Strategy</anno></c> is as in <c>deflateInit/6</c>. This can be + <p>Dynamically updates the compression level and compression + strategy. The interpretation of <c><anno>Level</anno></c> and + <c><anno>Strategy</anno></c> is as in + <seealso marker="#deflateInit/6"><c>deflateInit/6</c></seealso>. + This can be used to switch between compression and straight copy of the input data, or to switch to a different kind of input data requiring a different strategy. If the compression level is changed, the input available so far is compressed with the - old level (and may be flushed); the new level will take - effect only at the next call of <c>deflate/3</c>.</p> - <p>Before the call of <c>deflateParams</c>, the stream state must be set as for - a call of <c>deflate/3</c>, since the currently available input may have to - be compressed and flushed.</p> + old level (and can be flushed); the new level takes + effect only at the next call of + <seealso marker="#deflate/3"><c>deflate/3</c></seealso>.</p> + <p>Before the call of <c>deflateParams</c>, the stream state must be + set as for a call of <c>deflate/3</c>, as the currently available + input may have to be compressed and flushed.</p> </desc> </func> + <func> - <name name="deflateEnd" arity="1"/> - <fsummary>End deflate session</fsummary> + <name name="deflateReset" arity="1"/> + <fsummary>Reset the deflate session.</fsummary> + <desc> + <p>Equivalent to + <seealso marker="#deflateEnd/1"><c>deflateEnd/1</c></seealso> + followed by + <seealso marker="#deflateInit/1"><c>deflateInit/1,2,6</c></seealso>, + but does not free and reallocate all the internal compression state. + The stream keeps the same compression level and any other + attributes.</p> + </desc> + </func> + + <func> + <name name="deflateSetDictionary" arity="2"/> + <fsummary>Initialize the compression dictionary.</fsummary> <desc> - <p>End the deflate session and cleans all data used. - Note that this function will throw an <c>data_error</c> - exception if the last call to - <c>deflate/3</c> was not called with <c>Flush</c> set to - <c>finish</c>.</p> + <p>Initializes the compression dictionary from the specified byte + sequence without producing any compressed output.</p> + <p>This function must be called immediately after + <seealso marker="#deflateInit/1"><c>deflateInit/1,2,6</c></seealso> or + <seealso marker="#deflateReset/1"><c>deflateReset/1</c></seealso>, + before any call of + <seealso marker="#deflate/3"><c>deflate/3</c></seealso>. + The compressor and decompressor must use the same dictionary (see + <seealso marker="#inflateSetDictionary/2"> + <c>inflateSetDictionary/2</c></seealso>).</p> + <p>The Adler checksum of the dictionary is returned.</p> </desc> </func> + <func> - <name name="inflateInit" arity="1"/> - <fsummary>Initialize a session for decompression</fsummary> + <name name="getBufSize" arity="1"/> + <fsummary>Get buffer size.</fsummary> <desc> - <p>Initialize a zlib stream for decompression.</p> + <p>Gets the size of the intermediate buffer.</p> </desc> </func> + <func> - <name name="inflateInit" arity="2"/> - <fsummary>Initialize a session for decompression</fsummary> + <name name="gunzip" arity="1"/> + <fsummary>Uncompress data with gz header.</fsummary> <desc> - <p>Initialize decompression session on zlib stream.</p> - <p>The <c><anno>WindowBits</anno></c> parameter is the base two logarithm - of the maximum window size (the size of the history buffer). - It should be in the range 8 through 15. - The default value is 15 if <c>inflateInit/1</c> is used. - If a compressed stream with a larger window size is - given as input, inflate() will throw the <c>data_error</c> - exception. A negative <c><anno>WindowBits</anno></c> value makes zlib ignore the - zlib header (and checksum) from the stream. Note that the zlib - source mentions this only as a undocumented feature.</p> + <p>Uncompresses data with gz headers and checksum.</p> </desc> </func> + + <func> + <name name="gzip" arity="1"/> + <fsummary>Compress data with gz header.</fsummary> + <desc> + <p>Compresses data with gz headers and checksum.</p> + </desc> + </func> + <func> <name name="inflate" arity="2"/> - <fsummary>Decompress data</fsummary> + <fsummary>Decompress data.</fsummary> <desc> - <p><c>inflate/2</c> decompresses as much data as possible. - It may introduce some output latency (reading + <p>Decompresses as much data as possible. + It can introduce some output latency (reading input without producing any output).</p> <p>If a preset dictionary is needed at this point (see - <c>inflateSetDictionary</c> below), <c>inflate/2</c> throws a - <c>{need_dictionary,Adler}</c> exception where <c>Adler</c> is - the adler32 checksum of the dictionary chosen by the - compressor.</p> + <seealso marker="#inflateSetDictionary/2"> + <c>inflateSetDictionary/2</c></seealso>), <c>inflate/2</c> throws a + <c>{need_dictionary,Adler}</c> exception, where <c>Adler</c> is + the Adler-32 checksum of the dictionary chosen by the compressor.</p> + </desc> + </func> + + <func> + <name name="inflateChunk" arity="1"/> + <fsummary>Read next uncompressed chunk.</fsummary> + <desc> + <p>Reads the next chunk of uncompressed data, initialized by + <seealso marker="#inflateChunk/2"><c>inflateChunk/2</c></seealso>.</p> + <p>This function is to be repeatedly called, while it returns + <c>{more, Decompressed}</c>.</p> </desc> </func> + <func> <name name="inflateChunk" arity="2"/> - <fsummary>Decompress data with limited output size</fsummary> + <fsummary>Decompress data with limited output size.</fsummary> <desc> - <p>Like <c>inflate/2</c>, but decompress no more data than - will fit in the buffer configured via <c>setBufSize/2</c>. + <p>Like <seealso marker="#inflate/2"><c>inflate/2</c></seealso>, + but decompresses no more data than will fit in the buffer configured + through <seealso marker="#setBufSize/2"><c>setBufSize/2</c></seealso>. Is is useful when decompressing a stream with a high compression - ratio such that a small amount of compressed input may expand up to - 1000 times. - It returns <c>{more, Decompressed}</c>, when there is more output - available, and <c>inflateChunk/1</c> should be used to read it. - It may introduce some output latency (reading + ratio, such that a small amount of compressed input can expand up to + 1000 times.</p> + <p>This function returns <c>{more, Decompressed}</c>, when there is + more output available, and + <seealso marker="#inflateChunk/1"><c>inflateChunk/1</c></seealso> + is to be used to read it.</p> + <p>This function can introduce some output latency (reading input without producing any output).</p> <p>If a preset dictionary is needed at this point (see - <c>inflateSetDictionary</c> below), <c>inflateChunk/2</c> throws a - <c>{need_dictionary,Adler}</c> exception where <c>Adler</c> is - the adler32 checksum of the dictionary chosen by the - compressor.</p> - + <seealso marker="#inflateSetDictionary/2"> + <c>inflateSetDictionary/2</c></seealso>), this function throws a + <c>{need_dictionary,Adler}</c> exception, where <c>Adler</c> is + the Adler-32 checksum of the dictionary chosen by the compressor.</p> + <p>Example:</p> <pre> walk(Compressed, Handler) -> Z = zlib:open(), @@ -345,191 +501,126 @@ loop(Z, Handler, {more, Uncompressed}) -> Handler(Uncompressed), loop(Z, Handler, zlib:inflateChunk(Z)); loop(Z, Handler, Uncompressed) -> - Handler(Uncompressed). - </pre> - </desc> - </func> - <func> - <name name="inflateChunk" arity="1"/> - <fsummary>Read next uncompressed chunk</fsummary> - <desc> - <p>Read next chunk of uncompressed data, initialized by - <c>inflateChunk/2</c>.</p> - <p>This function should be repeatedly called, while it returns - <c>{more, Decompressed}</c>.</p> - </desc> - </func> - <func> - <name name="inflateSetDictionary" arity="2"/> - <fsummary>Initialize the decompression dictionary</fsummary> - <desc> - <p>Initializes the decompression dictionary from the given - uncompressed byte sequence. This function must be called - immediately after a call of <c>inflate/2</c> if this call - threw a <c>{need_dictionary,Adler}</c> exception. - The dictionary chosen by the - compressor can be determined from the Adler value thrown - by the call to <c>inflate/2</c>. The compressor and decompressor - must use exactly the same dictionary (see <c>deflateSetDictionary/2</c>).</p> - <p>Example:</p> - <pre> -unpack(Z, Compressed, Dict) -> - case catch zlib:inflate(Z, Compressed) of - {'EXIT',{{need_dictionary,DictID},_}} -> - zlib:inflateSetDictionary(Z, Dict), - Uncompressed = zlib:inflate(Z, []); - Uncompressed -> - Uncompressed - end.</pre> - </desc> - </func> - <func> - <name name="inflateReset" arity="1"/> - <fsummary>>Reset the inflate session</fsummary> - <desc> - <p>This function is equivalent to <c>inflateEnd/1</c> followed - by <c>inflateInit/1</c>, but does not free and reallocate all - the internal decompression state. The stream will keep - attributes that may have been set by <c>inflateInit/[1|2]</c>.</p> + Handler(Uncompressed).</pre> </desc> </func> + <func> <name name="inflateEnd" arity="1"/> - <fsummary>End inflate session</fsummary> + <fsummary>End inflate session.</fsummary> <desc> - <p>End the inflate session and cleans all data used. Note - that this function will throw a <c>data_error</c> exception + <p>Ends the inflate session and cleans all data used. Notice + that this function throws a <c>data_error</c> exception if no end of stream was found (meaning that not all data has been uncompressed).</p> </desc> </func> + <func> - <name name="setBufSize" arity="2"/> - <fsummary>Set buffer size</fsummary> - <desc> - <p>Sets the intermediate buffer size.</p> - </desc> - </func> - <func> - <name name="getBufSize" arity="1"/> - <fsummary>Get buffer size</fsummary> - <desc> - <p>Get the size of intermediate buffer.</p> - </desc> - </func> - <func> - <name name="crc32" arity="1"/> - <fsummary>Get current CRC</fsummary> - <desc> - <p>Get the current calculated CRC checksum.</p> - </desc> - </func> - <func> - <name name="crc32" arity="2"/> - <fsummary>Calculate CRC</fsummary> - <desc> - <p>Calculate the CRC checksum for <c><anno>Data</anno></c>.</p> - </desc> - </func> - <func> - <name name="crc32" arity="3"/> - <fsummary>Calculate CRC</fsummary> + <name name="inflateInit" arity="1"/> + <fsummary>Initialize a session for decompression.</fsummary> <desc> - <p>Update a running CRC checksum for <c><anno>Data</anno></c>. - If <c><anno>Data</anno></c> is the empty binary or the empty iolist, this function returns - the required initial value for the crc.</p> - <pre> -Crc = lists:foldl(fun(Data,Crc0) -> - zlib:crc32(Z, Crc0, Data), - end, zlib:crc32(Z,<< >>), Datas)</pre> + <p>Initializes a zlib stream for decompression.</p> </desc> </func> + <func> - <name name="crc32_combine" arity="4"/> - <fsummary>Combine two CRC's</fsummary> + <name name="inflateInit" arity="2"/> + <fsummary>Initialize a session for decompression.</fsummary> <desc> - <p>Combine two CRC checksums into one. For two binaries or iolists, - <c>Data1</c> and <c>Data2</c> with sizes of <c>Size1</c> and - <c><anno>Size2</anno></c>, with CRC checksums <c><anno>CRC1</anno></c> and - <c><anno>CRC2</anno></c>. <c>crc32_combine/4</c> returns the <c><anno>CRC</anno></c> - checksum of <c>[Data1,Data2]</c>, requiring - only <c><anno>CRC1</anno></c>, <c><anno>CRC2</anno></c>, and <c><anno>Size2</anno></c>. - </p> + <p>Initializes a decompression session on zlib stream.</p> + <p><c><anno>WindowBits</anno></c> is the base two logarithm + of the maximum window size (the size of the history buffer). + It is to be in the range 8 through 15. Default to 15 if + <seealso marker="#inflateInit/1"><c>inflateInit/1</c></seealso> + is used.</p> + <p>If a compressed stream with a larger window size is specified as + input, <seealso marker="#inflate/2"><c>inflate/2</c></seealso> + throws the <c>data_error</c> exception.</p> + <p>A negative <c><anno>WindowBits</anno></c> value makes zlib + ignore the zlib header (and checksum) from the stream. Notice that + the zlib source mentions this only as a undocumented feature.</p> </desc> </func> + <func> - <name name="adler32" arity="2"/> - <fsummary>Calculate the adler checksum</fsummary> + <name name="inflateReset" arity="1"/> + <fsummary>>Reset the inflate session.</fsummary> <desc> - <p>Calculate the Adler-32 checksum for <c><anno>Data</anno></c>.</p> + <p>Equivalent to + <seealso marker="#inflateEnd/1"><c>inflateEnd/1</c></seealso> + followed by + <seealso marker="#inflateInit/1"><c>inflateInit/1</c></seealso>, + but does not free and reallocate all the internal decompression state. + The stream will keep attributes that could have been set by + <c>inflateInit/1,2</c>.</p> </desc> </func> + <func> - <name name="adler32" arity="3"/> - <fsummary>Calculate the adler checksum</fsummary> + <name name="inflateSetDictionary" arity="2"/> + <fsummary>Initialize the decompression dictionary.</fsummary> <desc> - <p>Update a running Adler-32 checksum for <c><anno>Data</anno></c>. - If <c><anno>Data</anno></c> is the empty binary or the empty iolist, this function returns - the required initial value for the checksum.</p> + <p>Initializes the decompression dictionary from the specified + uncompressed byte sequence. This function must be called + immediately after a call of + <seealso marker="#inflate/2"><c>inflate/2</c></seealso> + if this call threw a <c>{need_dictionary,Adler}</c> exception. + The dictionary chosen by the compressor can be determined from the + Adler value thrown by the call to <c>inflate/2</c>. + The compressor and decompressor must use the same dictionary (see + <seealso marker="#deflateSetDictionary/2"> + <c>deflateSetDictionary/2</c></seealso>).</p> + <p>Example:</p> <pre> -Crc = lists:foldl(fun(Data,Crc0) -> - zlib:adler32(Z, Crc0, Data), - end, zlib:adler32(Z,<< >>), Datas)</pre> +unpack(Z, Compressed, Dict) -> + case catch zlib:inflate(Z, Compressed) of + {'EXIT',{{need_dictionary,DictID},_}} -> + zlib:inflateSetDictionary(Z, Dict), + Uncompressed = zlib:inflate(Z, []); + Uncompressed -> + Uncompressed + end.</pre> </desc> </func> + <func> - <name name="adler32_combine" arity="4"/> - <fsummary>Combine two Adler-32 checksums</fsummary> + <name name="open" arity="0"/> + <fsummary>Open a stream and return a stream reference.</fsummary> <desc> - <p>Combine two Adler-32 checksums into one. For two binaries or iolists, - <c>Data1</c> and <c>Data2</c> with sizes of <c>Size1</c> and - <c><anno>Size2</anno></c>, with Adler-32 checksums <c><anno>Adler1</anno></c> and - <c><anno>Adler2</anno></c>. <c>adler32_combine/4</c> returns the <c><anno>Adler</anno></c> - checksum of <c>[Data1,Data2]</c>, requiring - only <c><anno>Adler1</anno></c>, <c><anno>Adler2</anno></c>, and <c><anno>Size2</anno></c>. - </p> + <p>Opens a zlib stream.</p> </desc> </func> + <func> - <name name="compress" arity="1"/> - <fsummary>Compress data with standard zlib functionality</fsummary> + <name name="setBufSize" arity="2"/> + <fsummary>Set buffer size.</fsummary> <desc> - <p>Compress data (with zlib headers and checksum).</p> + <p>Sets the intermediate buffer size.</p> </desc> </func> + <func> <name name="uncompress" arity="1"/> - <fsummary>Uncompress data with standard zlib functionality</fsummary> + <fsummary>Uncompress data with standard zlib functionality.</fsummary> <desc> - <p>Uncompress data (with zlib headers and checksum).</p> - </desc> - </func> - <func> - <name name="zip" arity="1"/> - <fsummary>Compress data without the zlib headers</fsummary> - <desc> - <p>Compress data (without zlib headers and checksum).</p> + <p>Uncompresses data with zlib headers and checksum.</p> </desc> </func> + <func> <name name="unzip" arity="1"/> - <fsummary>Uncompress data without the zlib headers</fsummary> + <fsummary>Uncompress data without the zlib headers.</fsummary> <desc> - <p>Uncompress data (without zlib headers and checksum).</p> - </desc> - </func> - <func> - <name name="gzip" arity="1"/> - <fsummary>Compress data with gz header</fsummary> - <desc> - <p>Compress data (with gz headers and checksum).</p> + <p>Uncompresses data without zlib headers and checksum.</p> </desc> </func> + <func> - <name name="gunzip" arity="1"/> - <fsummary>Uncompress data with gz header</fsummary> + <name name="zip" arity="1"/> + <fsummary>Compress data without the zlib headers.</fsummary> <desc> - <p>Uncompress data (with gz headers and checksum).</p> + <p>Compresses data without zlib headers and checksum.</p> </desc> </func> </funcs> |