Lz4 Class

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The Lz4 class implements an LZ4 compressor and decompressor.

Class Name

IPWorksZip_Lz4

Procedural Interface

 ipworkszip_lz4_open();
 ipworkszip_lz4_close($res);
 ipworkszip_lz4_register_callback($res, $id, $function);
 ipworkszip_lz4_get_last_error($res);
 ipworkszip_lz4_get_last_error_code($res);
 ipworkszip_lz4_set($res, $id, $index, $value);
 ipworkszip_lz4_get($res, $id, $index);
 ipworkszip_lz4_do_compressblock($res, $lastblock);
 ipworkszip_lz4_do_compressdata($res);
 ipworkszip_lz4_do_config($res, $configurationstring);
 ipworkszip_lz4_do_decompressblock($res);
 ipworkszip_lz4_do_decompressdata($res);
 ipworkszip_lz4_do_reset($res);

Remarks

The Lz4 class is compliant with the LZ4 Frame Format specification. Data compressed by the class can be decompressed by any standard LZ4-compatible tool or library, and the class can in turn decompress data produced by any standard LZ4 encoder, including frames using linked blocks, block checksums, or skippable frames. Note that the legacy LZ4 frame format and LZ4 dictionaries are not supported, and frames using either are rejected with an error.

The CompressionLevel property selects the compression level to use, from 1 (fastest) to 6 (most compact).

Data may be operated on in multiple ways as discussed below.

Compression and Decompression Streams

The GetDecompressionStream and GetCompressionStream methods are used to retrieve streams that read or write compressed data, as appropriate. The underlying stream should be passed to either method as a parameter.

CompressBlock and DecompressBlock

The CompressBlock and DecompressBlock methods operate on blocks (chunks) of data. The methods may be used to compress and decompress data as they become available.

Note that when using blocks of data, the OutputData property is not applicable. Instead, data are made available via the CompressedData and DecompressedData events.

If all data is available ahead of time, the CompressData and DecompressData methods may be called instead.

Compress Data

THe InputData property should be set to the current block to be compressed. Next, the CompressBlock method should be called to compress the current block. Note that this method takes a LastBlock parameter; if the block of data is the final block to be compressed, it must be set to true. For all other blocks, it must remain false.

During compression, the CompressedData event will fire with the compressed data. Note that this event may not fire for every call to CompressBlock due to the way the compression algorithm operates.

zipstream.InputDataB = MyDecompressedData; zipstream.CompressBlock(); Data are accumulated inside the CompressedData event: private static void Zipstream_OnCompressedData(object sender, ZipstreamCompressedDataEventArgs e) { DoSomethingWith(e.DataB); }

Note that the OutputData property is not applicable when compressing block data.

Decompress Data

The InputData property should be set to the current block to be decompressed. Next, the DecompressBlock method should be called to decompress the current block.

During decompression, the DecompressedData event will fire with the decompressed data. Note that this event may not fire for every call to DecompressBlock due to the way the decompression algorithm operates.

zipstream.InputDataB = MyCompressedData; zipstream.DecompressBlock(); Data is accumulated inside the DecompressedData event: private static void Zipstream_OnDecompressedData(object sender, ZipstreamDecompressedDataEventArgs e) { DoSomethingWith(e.DataB); }

Note that the OutputData property is not applicable when decompressing block data.

CompressData and DecompressData

The CompressData and DecompressData methods operate on the complete blob of data. The entire compressed or decompressed data must be set to the InputData property before calling either method.

To compress and decompress data in blocks (chunks), refer to the CompressBlock and DecompressBlock methods.

Compress Data

The InputData property should be set to the decompressed data. This should be the entire data to be compressed. Next, the CompressData method should be called, after which the OutputData property will hold the compressed data.

zipstream.InputDataB = MyDecompressedData; zipstream.CompressData(); MyCompressedData = zipstream.OutputDataB;

In addition to OutputData, the compressed data may also be accumulated within the CompressedData event.

Decompress Data

The InputData property should be set to the compressed data. This should be the entire data to be decompressed. Next, the DecompressData method should be called, after which the OutputData property will hold the decompressed data.

zipstream.InputDataB = MyCompressedData; zipstream.DecompressData(); MyDecompressedData = zipstream.OutputDataB;

In addition to OutputData, the decompressed data may also be accumulated within the DecompressedData event.

Property List

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The following is the full list of the properties of the class with short descriptions. Click on the links for further details.

Method List

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The following is the full list of the methods of the class with short descriptions. Click on the links for further details.

Event List

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The following is the full list of the events fired by the class with short descriptions. Click on the links for further details.

Config Settings

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The following is a list of config settings for the class with short descriptions. Click on the links for further details.

CompressionLevel Property (IPWorksZip_Lz4 Class)

The compression level to use.

Object Oriented Interface

public function getCompressionLevel();
public function setCompressionLevel($value);

Procedural Interface

ipworkszip_lz4_get($res, 1);
ipworkszip_lz4_set($res, 1, $value);

Default Value

4

Remarks

This property dictates the compression level to use, from 1 to 6. Higher values will cause the class to compress better; lower values will cause the class to compress faster.

Data Type

Integer

InputData Property (IPWorksZip_Lz4 Class)

The data to compress or decompress.

Object Oriented Interface

public function getInputData();
public function setInputData($value);

Procedural Interface

ipworkszip_lz4_get($res, 2);
ipworkszip_lz4_set($res, 2, $value);

Default Value

''

Remarks

This property specifies the data to compress or decompress.

When decompressing, this should be set to the compressed data before the DecompressData or DecompressBlock methods are called.

When compressing, this should be set to the decompressed data before the CompressData or CompressBlock methods are called.

Note that this property is not automatically cleared after each operation when performing operations on multiple chunks of data.

Data Type

Binary String

OutputData Property (IPWorksZip_Lz4 Class)

The output data after compression or decompression.

Object Oriented Interface

public function getOutputData();

Procedural Interface

ipworkszip_lz4_get($res, 3);

Default Value

''

Remarks

This property holds the compressed or decompressed data after the CompressData or DecompressData methods are called.

This property is not applicable when calling the CompressBlock or DecompressBlock methods.

This property is read-only and not available at design time.

Data Type

Binary String

CompressBlock Method (IPWorksZip_Lz4 Class)

Compresses a block of data.

Object Oriented Interface

public function doCompressBlock($lastblock);

Procedural Interface

ipworkszip_lz4_do_compressblock($res, $lastblock);

Remarks

This method compresses the block of data specified by the InputData property.

The CompressBlock and DecompressBlock methods operate on blocks (chunks) of data. The methods may be used to compress and decompress data as they become available.

Note that when using blocks of data, the OutputData property is not applicable. Instead, data are made available via the CompressedData and DecompressedData events.

If all data is available ahead of time, the CompressData and DecompressData methods may be called instead.

Compress Data

The InputData property should be set to the current block to be compressed. Next, the CompressBlock method should be called to compress the current block. Note that this method takes a LastBlock parameter; if the block of data is the final block to be compressed, it must be set to true. For all other blocks, it must remain false.

During compression, the CompressedData event will fire with the compressed data. Note that this event may not fire for every call to CompressBlock due to the way the compression algorithm operates.

zipstream.InputDataB = MyDecompressedData; zipstream.CompressBlock(); Data are accumulated inside the CompressedData event: private static void Zipstream_OnCompressedData(object sender, ZipstreamCompressedDataEventArgs e) { DoSomethingWith(e.DataB); }

Note that the OutputData property is not applicable when compressing block data.

Decompress Data

The InputData property should be set to the current block to be decompressed. Next, the DecompressBlock method should be called to decompress the current block.

During decompression, the DecompressedData event will fire with the decompressed data. Note that this event may not fire for every call to DecompressBlock due to the way the decompression algorithm operates.

zipstream.InputDataB = MyCompressedData; zipstream.DecompressBlock(); Data is accumulated inside the DecompressedData event: private static void Zipstream_OnDecompressedData(object sender, ZipstreamDecompressedDataEventArgs e) { DoSomethingWith(e.DataB); }

Note that the OutputData property is not applicable when decompressing block data.

CompressData Method (IPWorksZip_Lz4 Class)

Compresses the specified data.

Object Oriented Interface

public function doCompressData();

Procedural Interface

ipworkszip_lz4_do_compressdata($res);

Remarks

This method compresses the data specified by the InputData property. After calling this method, the OutputData property holds the compressed data.

The CompressData and DecompressData methods operate on the complete blob of data. The entire compressed or decompressed data must be set to the InputData property before calling either method.

To compress and decompress data in blocks (chunks), refer to the CompressBlock and DecompressBlock methods.

Compress Data

The InputData property should be set to the decompressed data. This should be the entire data to be compressed. Next, the CompressData method should be called, after which the OutputData property will hold the compressed data.

zipstream.InputDataB = MyDecompressedData; zipstream.CompressData(); MyCompressedData = zipstream.OutputDataB;

In addition to OutputData, the compressed data may also be accumulated within the CompressedData event.

Decompress Data

The InputData property should be set to the compressed data. This should be the entire data to be decompressed. Next, the DecompressData method should be called, after which the OutputData property will hold the decompressed data.

zipstream.InputDataB = MyCompressedData; zipstream.DecompressData(); MyDecompressedData = zipstream.OutputDataB;

In addition to OutputData, the decompressed data may also be accumulated within the DecompressedData event.

Config Method (IPWorksZip_Lz4 Class)

Sets or retrieves a configuration setting.

Object Oriented Interface

public function doConfig($configurationstring);

Procedural Interface

ipworkszip_lz4_do_config($res, $configurationstring);

Remarks

Config is a generic method available in every class. It is used to set and retrieve configuration settings for the class.

These settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the class, access to these internal properties is provided through the Config method.

To set a configuration setting named PROPERTY, you must call Config("PROPERTY=VALUE"), where VALUE is the value of the setting expressed as a string. For boolean values, use the strings "True", "False", "0", "1", "Yes", or "No" (case does not matter).

To read (query) the value of a configuration setting, you must call Config("PROPERTY"). The value will be returned as a string.

DecompressBlock Method (IPWorksZip_Lz4 Class)

Decompresses a block of data.

Object Oriented Interface

public function doDecompressBlock();

Procedural Interface

ipworkszip_lz4_do_decompressblock($res);

Remarks

This method decompresses the block of data specified by the InputData property.

The CompressBlock and DecompressBlock methods operate on blocks (chunks) of data. The methods may be used to compress and decompress data as they become available.

Note that when using blocks of data, the OutputData property is not applicable. Instead, data are made available via the CompressedData and DecompressedData events.

If all data is available ahead of time, the CompressData and DecompressData methods may be called instead.

Compress Data

The InputData property should be set to the current block to be compressed. Next, the CompressBlock method should be called to compress the current block. Note that this method takes a LastBlock parameter; if the block of data is the final block to be compressed, it must be set to true. For all other blocks, it must remain false.

During compression, the CompressedData event will fire with the compressed data. Note that this event may not fire for every call to CompressBlock due to the way the compression algorithm operates.

zipstream.InputDataB = MyDecompressedData; zipstream.CompressBlock(); Data are accumulated inside the CompressedData event: private static void Zipstream_OnCompressedData(object sender, ZipstreamCompressedDataEventArgs e) { DoSomethingWith(e.DataB); }

Note that the OutputData property is not applicable when compressing block data.

Decompress Data

The InputData property should be set to the current block to be decompressed. Next, the DecompressBlock method should be called to decompress the current block.

During decompression, the DecompressedData event will fire with the decompressed data. Note that this event may not fire for every call to DecompressBlock due to the way the decompression algorithm operates.

zipstream.InputDataB = MyCompressedData; zipstream.DecompressBlock(); Data is accumulated inside the DecompressedData event: private static void Zipstream_OnDecompressedData(object sender, ZipstreamDecompressedDataEventArgs e) { DoSomethingWith(e.DataB); }

Note that the OutputData property is not applicable when decompressing block data.

DecompressData Method (IPWorksZip_Lz4 Class)

Decompresses the specified data.

Object Oriented Interface

public function doDecompressData();

Procedural Interface

ipworkszip_lz4_do_decompressdata($res);

Remarks

This method decompresses the data specified by the InputData property. After calling this method, the OutputData property holds the decompressed data.

The CompressData and DecompressData methods operate on the complete blob of data. The entire compressed or decompressed data must be set to the InputData property before calling either method.

To compress and decompress data in blocks (chunks), refer to the CompressBlock and DecompressBlock methods.

Compress Data

The InputData property should be set to the decompressed data. This should be the entire data to be compressed. Next, the CompressData method should be called, after which the OutputData property will hold the compressed data.

zipstream.InputDataB = MyDecompressedData; zipstream.CompressData(); MyCompressedData = zipstream.OutputDataB;

In addition to OutputData, the compressed data may also be accumulated within the CompressedData event.

Decompress Data

The InputData property should be set to the compressed data. This should be the entire data to be decompressed. Next, the DecompressData method should be called, after which the OutputData property will hold the decompressed data.

zipstream.InputDataB = MyCompressedData; zipstream.DecompressData(); MyDecompressedData = zipstream.OutputDataB;

In addition to OutputData, the decompressed data may also be accumulated within the DecompressedData event.

Reset Method (IPWorksZip_Lz4 Class)

Resets the class.

Object Oriented Interface

public function doReset();

Procedural Interface

ipworkszip_lz4_do_reset($res);

Remarks

This method is used to reset the state of the class. All properties are set to their default values, and any open files are closed.

CompressedData Event (IPWorksZip_Lz4 Class)

Fires with compressed data.

Object Oriented Interface

public function fireCompressedData($param);

Procedural Interface

ipworkszip_lz4_register_callback($res, 1, array($this, 'fireCompressedData'));

Parameter List

'data'

Remarks

This event is fired one or more times as compressed data become available when the CompressData or CompressBlock methods are called.

Data holds the current block of compressed data.

DecompressedData Event (IPWorksZip_Lz4 Class)

Fires with decompressed data.

Object Oriented Interface

public function fireDecompressedData($param);

Procedural Interface

ipworkszip_lz4_register_callback($res, 2, array($this, 'fireDecompressedData'));

Parameter List

'data'

Remarks

This event is fired one or more times as decompressed data become available when the DecompressData or DecompressBlock methods are called.

Data holds the current block of decompressed data.

Error Event (IPWorksZip_Lz4 Class)

Fires with information about errors during data delivery.

Object Oriented Interface

public function fireError($param);

Procedural Interface

ipworkszip_lz4_register_callback($res, 3, array($this, 'fireError'));

Parameter List

'errorcode'
'description'

Remarks

This event is fired in case of exceptional conditions during message processing. Normally, the class fails with an error.

ErrorCode contains an error code and Description contains a textual description of the error. For a list of valid error codes and their descriptions, please refer to the Error Codes section.

Config Settings (Lz4 Class)

The class accepts one or more of the following configuration settings . Configuration settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the class, access to these internal properties is provided through the Config method.

No configuration settings defined.

Base Config Settings

Trappable Errors (Lz4 Class)

Note that the streams returned by GetCompressionStream and GetDecompressionStream will throw standard IOExceptions in case of error.

ZipStream Errors