Lz4 Class

Properties   Methods   Events   Config Settings   Errors  

The Lz4 class implements an LZ4 compressor and decompressor.

Syntax

ipworkszip.lz4()

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

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

Method List

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

Event List

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

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

Lz4.CloseBaseStream Property

Whether or not to close the underlying stream.

Syntax

isCloseBaseStream(): boolean;
setCloseBaseStream(closeBaseStream: boolean): void;

Default Value

true

Remarks

This property controls whether streams created via the GetCompressionStream and GetDecompressionStream methods will close their underlying streams when their Close method is invoked.

When enabled, the underlying streams are closed; otherwise, they will remain open.

Lz4.CompressionLevel Property

The compression level to use.

Syntax

getCompressionLevel(): number;
setCompressionLevel(compressionLevel: number): void;

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.

When the GetCompressionStream method is invoked, the stream will be created with the specified compression level. After a stream has been created, it is independent of the class, and changing this property will have no effect on existing streams.

Lz4.InputData Property

The data to compress or decompress.

Syntax

getInputData(): string;
getInputDataB(): Uint8Array | null;
setInputData(inputData: Uint8Array | string): void;

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.

Lz4.OutputData Property

The output data after compression or decompression.

Syntax

getOutputData(): string;
getOutputDataB(): Uint8Array | null;

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.

Lz4.compressBlock Method

Compresses a block of data.

Syntax

async lz4.compressBlock(lastBlock : boolean): Promise<void>

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.

Lz4.compressData Method

Compresses the specified data.

Syntax

async lz4.compressData(): Promise<void>

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.

Lz4.config Method

Sets or retrieves a configuration setting.

Syntax

async lz4.config(configurationString : string | null): Promise<string | null>

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.

Lz4.decompressBlock Method

Decompresses a block of data.

Syntax

async lz4.decompressBlock(): Promise<void>

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.

Lz4.decompressData Method

Decompresses the specified data.

Syntax

async lz4.decompressData(): Promise<void>

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.

Lz4.getCompressionStream Method

Creates an output stream used to write compressed data.

Syntax

async lz4.getCompressionStream(baseStream : WriteableStream | null): Promise<WriteableStream | null>

Remarks

This method returns a stream used to compress data as they are written to an underlying stream. The BaseStream parameter should be set to the stream to which the compressed data will be written.

The returned stream is independent of the class once created; thus, subsequently changing the CompressionLevel property has no effect on it. Closing the returned stream also closes BaseStream if the CloseBaseStream property is enabled before the stream is created.

Lz4.getDecompressionStream Method

Creates an input stream used to read data from a compressed stream.

Syntax

async lz4.getDecompressionStream(baseStream : ReadableStream | null): Promise<ReadableStream | null>

Remarks

This method returns a stream used to read decompressed data as they are read from an underlying compressed stream. The BaseStream parameter should be set to the stream providing the compressed data.

The returned stream is independent of the class once created. Closing the returned stream also closes BaseStream if the CloseBaseStream property is enabled before the stream is created.

Lz4.reset Method

Resets the class.

Syntax

async lz4.reset(): Promise<void>

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.

Lz4.CompressedData Event

Fires with compressed data.

Syntax

lz4.on('CompressedData', listener: (e: {readonly data: string, readonly dataB: Uint8Array | null}) => void )

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.

Lz4.DecompressedData Event

Fires with decompressed data.

Syntax

lz4.on('DecompressedData', listener: (e: {readonly data: string, readonly dataB: Uint8Array | null}) => void )

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.

Lz4.Error Event

Fires with information about errors during data delivery.

Syntax

lz4.on('Error', listener: (e: {readonly errorCode: number, readonly description: string | null}) => void )

Remarks

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

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.

ReadableStream Type

Syntax

interface ReadableStream {
  read(buffer: Uint8Array, offset: number, length: number): Promise<number>;
  readSync(buffer: Uint8Array, offset: number, length: number): number;
  available(): number;
  close(): void;
  mark(): void;
  reset(): void;
  markSupported(): boolean;
}

Remarks

The Lz4 class includes one or more API methods that accept a stream object as a parameter. To use such API members, create a custom object that implements the ReadableStream interface, and pass an instance of this object to the Lz4 class.

When implementing the ReadableStream interface's properties and methods, they must behave as described below. If the implementation does not behave as expected, undefined behavior may occur.

read(buffer: Uint8Array, offset: number, length: number): Promise <number> { }

readSync(buffer: Uint8Array, offset: number, length: number): number { }

available(): number { }

close(): void { }

mark(): void { }

reset(): void { }

markSupported(): boolean { }

WriteableStream Type

Syntax

interface WriteableStream {
  write(data: Uint8Array, offset: number, length: number): Promise<void>;
  writeSync(data: Uint8Array, offset: number, length: number): void;
  close(): void;
}

Remarks

The Lz4 class includes one or more API methods that accept a stream object as a parameter. To use such API members, create a custom object that implements the WriteableStream interface, and pass an instance of this object to the Lz4 class.

When implementing the WriteableStream interface's properties and methods, they must behave as described below. If the implementation does not behave as expected, undefined behavior may occur.

write(data: Uint8Array, offset: number, length: number): Promise <void> { }

writeSync(data: Uint8Array, offset: number, length: number): void { }

close(): void { }

Config Settings (Lz4 Class)

No configuration settings defined.

Base Config Settings

Trappable Errors (Lz4 Class)

ZipStream Errors