ZipStream Control
Properties Methods Events Configuration Settings Errors
The ZipStream control is used to perform compression or decompression.
Syntax
ZipStream
Remarks
The ZipStream control provides a way to compress and decompress streamed data.
Data may be operated on in multiple ways as discussed below. The StreamFormat property specifies the algorithm to us. Possible values are:
- Deflate
- Zlib
- Gzip
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 it becomes available.
Note that when using blocks of data the OutputData property is not applicable. Instead data is made available through the CompressedData and DecompressedData events.
If all data is available ahead of time CompressData and DecompressData may be called instead.
Compress Data
Set InputData to the current block to be compressed. Next call CompressBlock to compress the current block. Note that CompressBlock takes a LastBlock parameter. If the block of data is the final block to be compressed set this to True. For all other blocks set this to 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. For example:
zipstream.InputDataB = MyDecompressedData;
zipstream.CompressBlock();
Data is accumulated inside the CompressedData event:
private static void Zipstream_OnCompressedData(object sender, ZipstreamCompressedDataEventArgs e)
{
DoSomethingWith(e.DataB);
}
Note that OutputData is not applicable when compressing block data.
Decompress Data
Set InputData to the current block to be decompressed. Next call DecompressBlock 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. For example:
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 OutputData 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 InputData before calling either method.
To compress and decompress data in blocks (chunks) see CompressBlock and DecompressBlock.
Compress Data
Set InputData to the decompressed data. This should be the entire data to be compressed. Next call CompressData. After compression OutputData will hold the compressed data. For example:
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
Set InputData to the compressed data. This should be the entire data to be decompressed. Next call DecompressData. After decompression OutputData will hold the decompressed data. For example:
zipstream.InputDataB = MyCompressedData;
zipstream.DecompressData();
MyDecompressedData = zipstream.OutputDataB;
In addition to OutputData, the compressed data may also be accumulated within the DecompressedData event.
Property List
The following is the full list of the properties of the control with short descriptions. Click on the links for further details.
| CompressionLevel | The compression level to use. |
| InputData | Specifies the data to compress or decompress. |
| OutputData | The output data after compression or decompression. |
| StreamFormat | The stream format to use. |
Method List
The following is the full list of the methods of the control with short descriptions. Click on the links for further details.
| CompressBlock | Compresses a block of data. |
| CompressData | Compresses the specified data. |
| Config | Sets or retrieves a configuration setting. |
| DecompressBlock | Decompresses a block of data. |
| DecompressData | Decompresses the specified data. |
| Reset | Resets the control. |
Event List
The following is the full list of the events fired by the control with short descriptions. Click on the links for further details.
| CompressedData | This event fires with compressed data. |
| DecompressedData | This event fires with decompressed data. |
| Error | Information about errors during data delivery. |
Configuration Settings
The following is a list of configuration settings for the control with short descriptions. Click on the links for further details.
| CodePage | The system code page used for Unicode to Multibyte translations. |
| UseInternalSecurityAPI | Tells the control whether or not to use the system security libraries or an internal implementation. |
CompressionLevel Property (ZipStream Control)
The compression level to use.
Syntax
zipstreamcontrol.CompressionLevel[=integer]
Default Value
4
Remarks
The compression level to use, from 1 to 6. Higher values will cause the component to compress better; lower values will cause the component to compress faster.
When GetCompressionStream is invoked the stream will be created with the specified compression level. After a stream has been created it is independent of the control, and changing CompressionLevel will have no effect on existing streams.
Data Type
Integer
InputData Property (ZipStream Control)
Specifies the data to compress or decompress.
Syntax
zipstreamcontrol.InputData[=string]
Default Value
""
Remarks
This property specifies the data to compress or decompress.
When decompressing this should be set to the compressed data before calling DecompressData or DecompressBlock.
When compressing this should be set to the decompressed data before calling CompressData or CompressBlock.
To read or write binary data to the property, a Variant (Byte Array) version is provided in .InputDataB.
Data Type
Binary String
OutputData Property (ZipStream Control)
The output data after compression or decompression.
Syntax
zipstreamcontrol.OutputData
Default Value
""
Remarks
This property holds the compressed or decompressed data after CompressData or DecompressData is called.
This property is not applicable when calling CompressBlock or DecompressBlock.
To read or write binary data to the property, a Variant (Byte Array) version is provided in .OutputDataB.
This property is read-only and not available at design time.
Data Type
Binary String
StreamFormat Property (ZipStream Control)
The stream format to use.
Syntax
zipstreamcontrol.StreamFormat[=integer]
Possible Values
sfDeflate(0), sfZlib(1), sfGzip(2)
Default Value
0
Remarks
The stream format to use, by default Deflate.
All three stream formats use the Deflate algorithm specified in RFC 1951, which is the same algorithm used by Zip. The Zlib stream format adds a two-byte header and an Adler-32 checksum; the Gzip format adds a longer header and a CRC checksum, and is identical to the Gzip file format.
Caution: The terms zlib and deflate are sometimes used interchangeably (which is technically incorrect).
Data Type
Integer
CompressBlock Method (ZipStream Control)
Compresses a block of data.
Syntax
zipstreamcontrol.CompressBlock LastBlock
Remarks
This method compresses the block of data specified by InputData.
The CompressBlock and DecompressBlock methods operate on blocks (chunks) of data. The methods may be used to compress and decompress data as it becomes available.
Note that when using blocks of data the OutputData property is not applicable. Instead data is made available through the CompressedData and DecompressedData events.
If all data is available ahead of time CompressData and DecompressData may be called instead.
Compress Data
Set InputData to the current block to be compressed. Next call CompressBlock to compress the current block. Note that CompressBlock takes a LastBlock parameter. If the block of data is the final block to be compressed set this to True. For all other blocks set this to 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. For example:
zipstream.InputDataB = MyDecompressedData;
zipstream.CompressBlock();
Data is accumulated inside the CompressedData event:
private static void Zipstream_OnCompressedData(object sender, ZipstreamCompressedDataEventArgs e)
{
DoSomethingWith(e.DataB);
}
Note that OutputData is not applicable when compressing block data.
Decompress Data
Set InputData to the current block to be decompressed. Next call DecompressBlock 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. For example:
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 OutputData is not applicable when decompressing block data.
CompressData Method (ZipStream Control)
Compresses the specified data.
Syntax
zipstreamcontrol.CompressData
Remarks
This method compresses the data specified by InputData. After calling this method OutputData 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 InputData before calling either method.
To compress and decompress data in blocks (chunks) see CompressBlock and DecompressBlock.
Compress Data
Set InputData to the decompressed data. This should be the entire data to be compressed. Next call CompressData. After compression OutputData will hold the compressed data. For example:
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
Set InputData to the compressed data. This should be the entire data to be decompressed. Next call DecompressData. After decompression OutputData will hold the decompressed data. For example:
zipstream.InputDataB = MyCompressedData;
zipstream.DecompressData();
MyDecompressedData = zipstream.OutputDataB;
In addition to OutputData, the compressed data may also be accumulated within the DecompressedData event.
Config Method (ZipStream Control)
Sets or retrieves a configuration setting.
Syntax
zipstreamcontrol.Config ConfigurationString
Remarks
Config is a generic method available in every control. It is used to set and retrieve configuration settings for the control.
These settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the control, 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 (ZipStream Control)
Decompresses a block of data.
Syntax
zipstreamcontrol.DecompressBlock
Remarks
This method decompresses the block of data specified by InputData.
The CompressBlock and DecompressBlock methods operate on blocks (chunks) of data. The methods may be used to compress and decompress data as it becomes available.
Note that when using blocks of data the OutputData property is not applicable. Instead data is made available through the CompressedData and DecompressedData events.
If all data is available ahead of time CompressData and DecompressData may be called instead.
Compress Data
Set InputData to the current block to be compressed. Next call CompressBlock to compress the current block. Note that CompressBlock takes a LastBlock parameter. If the block of data is the final block to be compressed set this to True. For all other blocks set this to 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. For example:
zipstream.InputDataB = MyDecompressedData;
zipstream.CompressBlock();
Data is accumulated inside the CompressedData event:
private static void Zipstream_OnCompressedData(object sender, ZipstreamCompressedDataEventArgs e)
{
DoSomethingWith(e.DataB);
}
Note that OutputData is not applicable when compressing block data.
Decompress Data
Set InputData to the current block to be decompressed. Next call DecompressBlock 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. For example:
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 OutputData is not applicable when decompressing block data.
DecompressData Method (ZipStream Control)
Decompresses the specified data.
Syntax
zipstreamcontrol.DecompressData
Remarks
This method decompresses the data specified by InputData. After calling this method OutputData 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 InputData before calling either method.
To compress and decompress data in blocks (chunks) see CompressBlock and DecompressBlock.
Compress Data
Set InputData to the decompressed data. This should be the entire data to be compressed. Next call CompressData. After compression OutputData will hold the compressed data. For example:
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
Set InputData to the compressed data. This should be the entire data to be decompressed. Next call DecompressData. After decompression OutputData will hold the decompressed data. For example:
zipstream.InputDataB = MyCompressedData;
zipstream.DecompressData();
MyDecompressedData = zipstream.OutputDataB;
In addition to OutputData, the compressed data may also be accumulated within the DecompressedData event.
Reset Method (ZipStream Control)
Resets the control.
Syntax
zipstreamcontrol.Reset
Remarks
Reset resets the state of the control. All properties will be set to their default values, and any files open will be closed.
CompressedData Event (ZipStream Control)
This event fires with compressed data.
Syntax
Sub zipstreamcontrol_CompressedData(Data As String)
Remarks
The CompressedData event fires as compressed data is available when CompressData or CompressBlock is called. This may fire one or more times when data is compressed.
Data holds the current block of compressed data.
DecompressedData Event (ZipStream Control)
This event fires with decompressed data.
Syntax
Sub zipstreamcontrol_DecompressedData(Data As String)
Remarks
The DecompressedData event fires as compressed data is available when DecompressData or DecompressBlock is called. This may fire one or more times as data is decompressed.
Data holds the current block of decompressed data.
Error Event (ZipStream Control)
Information about errors during data delivery.
Syntax
Sub zipstreamcontrol_Error(ErrorCode As Integer, Description As String)
Remarks
The Error event is fired in case of exceptional conditions during message processing. Normally the control 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.
Configuration Settings (ZipStream Control)
The control 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 control, access to these internal properties is provided through the Config method.No configuration settings defined.
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| CodePage:
The system code page used for Unicode to Multibyte translations.The default code page is Unicode UTF-8 (65001).
The following is a list of valid code page identifiers:
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| UseInternalSecurityAPI: Tells the control whether or not to use the system security libraries or an internal implementation. By default the control will use the system security libraries to perform cryptographic functions where applicable. Setting this to tells the control to use the internal implementation instead of using the system's security API. |
Trappable Errors (ZipStream Control)
Note that the streams returned by GetCompressionStream and GetDecompressionStream will throw standard IOExceptions in case of error.ZipStream Errors
| 20102 The data is of an invalid or unsupported format. | |
| 20112 Can't open file for read. | |
| 20151 An I/O error has occurred (details follow). |