Compression VB.NET Reference Documentation
Compression
Current Version: 11.0.0
Implements the Bzip2, Deflate, and LZW compression algorithms.
Object Creation
Dim obj As New Chilkat.Compression()
Properties
Algorithm
Specifies the compression algorithm: deflate
, zlib
, bzip2
, or lzw
. Note that ppmd
is deprecated and should not be used. It was only available for 32-bit systems and specifically used the J
variant. Please transition to one of the recommended algorithms.
Charset
This property specifies the character encoding used to represent text as bytes for compression and decompression. By default, it uses the computer's ANSI
charset, such as Windows-1252 for locales like the United States, United Kingdom, Western Europe, Australia, and New Zealand.
Most applications are advised to set this property to UTF-8
. Chilkat plans to change its default to UTF-8 in a future major version to align with current standards. The current default of ANSI stems from a time when UTF-8 was not widely adopted.
DebugLogFilePath
If set to a file path, this property logs the LastErrorText of each Chilkat method or property call to the specified file. This logging helps identify the context and history of Chilkat calls leading up to any crash or hang, aiding in debugging.
Enabling the VerboseLogging property provides more detailed information. This property is mainly used for debugging rare instances where a Chilkat method call causes a hang or crash, which should generally not happen.
Possible causes of hangs include:
- A timeout property set to 0, indicating an infinite timeout.
- A hang occurring within an event callback in the application code.
- An internal bug in the Chilkat code causing the hang.
DeflateLevel
This property allows for customization of the compression level for the deflate
and zlib
compression algoirthms. (zlib
is just the deflate algorithm with a zlib header.) A value of 0 = no compression, while 9 = maximum compression. The default is 6.
EncodingMode
Controls the encoding expected by methods ending in ENC
, such as CompressBytesENC. Valid values are base64
, hex
, url
, and quoted-printable
. Compression methods ending in ENC return the binary compressed data as an encoded string using this encoding. Decompress methods expect the input string to be this encoding.
FirstChunk
This property applies to FirstChunk
and LastChunk
aware compression and decompression methods. It signifies that the data being compressed is the first of multiple chunks.
The default value is True
.
When both FirstChunk
and LastChunk
are set to True
, it means the entire amount of data to be compressed or decompressed is presented in a single call.
HeartbeatMs
The interval in milliseconds between each AbortCheck
event callback, which enables an application to abort certain method calls before they complete. By default, HeartbeatMs is set to 0
, meaning no AbortCheck event callbacks will trigger.
LastChunk
This property applies to FirstChunk
and LastChunk
aware compression and decompression methods. It signifies that the data being compressed is the last of multiple chunks.
The default value is True
.
When both FirstChunk
and LastChunk
are set to True
, it means the entire amount of data to be compressed or decompressed is presented in a single call.
LastErrorHtml
Provides HTML-formatted information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.
topLastErrorText
Provides plain text information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.
LastErrorXml
Provides XML-formatted information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.
topLastMethodSuccess
Indicates the success or failure of the most recent method call: True
means success, False
means failure. This property remains unchanged by property setters or getters. This method is present to address challenges in checking for null or Nothing returns in certain programming languages.
UncommonOptions
This is a catch-all property to be used for uncommon needs. This property defaults to the empty string and should typically remain empty.
Can be set to a list of the following comma separated keywords:
Crypt2CompressHdr
- Duplicates the compression and decompression as implemented in the deprecated and removed Crypt2 compression functions.
VerboseLogging
If set to True
, then the contents of LastErrorText (or LastErrorXml, or LastErrorHtml) may contain more verbose information. The default value is False
. Verbose logging should only be used for debugging. The potentially large quantity of logged information may adversely affect peformance.
Version
Methods
CompressBd
Compresses the data contained in bd. This method is not FirstChunk
/LastChunk
aware.
Returns True for success, False for failure.
CompressBdAsync (1)
Creates an asynchronous task to call the CompressBd method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nothing
on failure
CompressBd2
This method compresses the data in bdIn without modifying it and appends the compressed data to bdOut. It is also FirstChunk
/LastChunk
aware.
Returns True for success, False for failure.
topCompressBd2Async (1)
Creates an asynchronous task to call the CompressBd2 method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nothing
on failure
CompressBytes
Compresses byte data.
This method is FirstChunk
/LastChunk
aware.
Returns an empty byte array on failure
CompressBytesAsync (1)
Creates an asynchronous task to call the CompressBytes method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nothing
on failure
CompressBytesENC
Compresses bytes and returns the compressed data encoded to a string. The encoding (hex, base64, etc.) is determined by the EncodingMode property setting.
Returns Nothing
on failure
CompressBytesENCAsync (1)
Creates an asynchronous task to call the CompressBytesENC method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nothing
on failure
CompressEncryptFile
Performs file-to-file compression and encryption. Files of any size may be compressed because the file is compressed and encrypted internally in streaming mode.
Returns True for success, False for failure.
CompressEncryptFileAsync (1)
Creates an asynchronous task to call the CompressEncryptFile method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nothing
on failure
CompressFile
Performs file-to-file compression. Files of any size may be compressed because the file is compressed internally in streaming mode.
Returns True for success, False for failure.
CompressFileAsync (1)
Creates an asynchronous task to call the CompressFile method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nothing
on failure
CompressSb
Compresses the contents of sb and appends the compressed bytes to binData.
This method is FirstChunk
/LastChunk
aware.
Returns True for success, False for failure.
topCompressSbAsync (1)
Creates an asynchronous task to call the CompressSb method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nothing
on failure
CompressStr
Compresses a string and appends to bd. The byte representation (character encoding) of the actual bytes to be compressed is determined by the Charset
property. This method is FirstChunk
/ LastChunk
aware.
Returns True for success, False for failure.
topCompressStrAsync (1)
Creates an asynchronous task to call the CompressStr method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nothing
on failure
CompressStream
Compresses a stream. Internally, the strm's source is read, compressed, and the compressed data written to the strm's sink. It does this in streaming fashion. Extremely large or even infinite streams can be compressed with stable ungrowing memory usage.
Returns True for success, False for failure.
CompressStreamAsync (1)
Creates an asynchronous task to call the CompressStream method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nothing
on failure
CompressString
Compresses a string.
This method is FirstChunk
/LastChunk
aware.
Returns an empty byte array on failure
CompressStringAsync (1)
Creates an asynchronous task to call the CompressString method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nothing
on failure
CompressStringENC
Compresses a string and returns the compressed data encoded to a string. The output encoding (hex, base64, etc.) is determined by the EncodingMode property setting. This method is NOT FirstChunk
/LastChunk
aware.
Returns Nothing
on failure
CompressStringENCAsync (1)
Creates an asynchronous task to call the CompressStringENC method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nothing
on failure
DecompressBd
Decompresses the data contained in bd. This method is NOT FirstChunk
/LastChunk
aware.
Returns True for success, False for failure.
DecompressBdAsync (1)
Creates an asynchronous task to call the DecompressBd method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nothing
on failure
DecompressBd2
This method decompresses the data in bdIn without modifying it and appends the decompressed data to bdOut. It is also FirstChunk
/LastChunk
aware.
Returns True for success, False for failure.
topDecompressBd2Async (1)
Creates an asynchronous task to call the DecompressBd2 method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nothing
on failure
DecompressBytes
This method decompresses bytes.
This method is FirstChunk
/LastChunk
aware.
Returns an empty byte array on failure
DecompressBytesAsync (1)
Creates an asynchronous task to call the DecompressBytes method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nothing
on failure
DecompressBytesENC
The opposite of CompressBytesENC. encodedCompressedData contains the compressed data as an encoded string (hex, base64, etc) as specified by the EncodingMode property setting.
Returns an empty byte array on failure
DecompressBytesENCAsync (1)
Creates an asynchronous task to call the DecompressBytesENC method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nothing
on failure
DecompressFile
Performs file-to-file decompression (the opposite of CompressFile). Internally the file is decompressed in streaming mode which allows files of any size to be decompressed.
Returns True for success, False for failure.
DecompressFileAsync (1)
Creates an asynchronous task to call the DecompressFile method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nothing
on failure
DecompressSb
Decompresses the contents of binData and appends the decompressed string to sb.
This method is FirstChunk
/LastChunk
aware.
Returns True for success, False for failure.
topDecompressSbAsync (1)
Creates an asynchronous task to call the DecompressSb method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nothing
on failure
DecompressStream
Decompresses a stream. Internally, the strm's source is read, decompressed, and the decompressed data written to the strm's sink. It does this in streaming fashion. Extremely large or even infinite streams can be decompressed with stable ungrowing memory usage.
Returns True for success, False for failure.
DecompressStreamAsync (1)
Creates an asynchronous task to call the DecompressStream method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nothing
on failure
DecompressString
Takes compressed bytes, decompresses, and returns the resulting string.
This method is FirstChunk
/LastChunk
aware.
Returns Nothing
on failure
DecompressStringENC
The opposite of CompressStringENC. encodedCompressedData contains the compressed data as an encoded string (hex, base64, etc) as specified by the EncodingMode property setting. This method is NOT FirstChunk
/LastChunk
aware.
Returns Nothing
on failure
DecompressStringENCAsync (1)
Creates an asynchronous task to call the DecompressStringENC method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nothing
on failure
DecryptDecompressFile
Performs file-to-file decryption and decompression.
Returns True for success, False for failure.
DecryptDecompressFileAsync (1)
Creates an asynchronous task to call the DecryptDecompressFile method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nothing
on failure
LoadTaskCaller
Events
AbortCheck
Enables a method call to be aborted by triggering the AbortCheck event at intervals defined by the HeartbeatMs
property. If HeartbeatMs is set to its default value of 0, no events will occur. For instance, set HeartbeatMs to 200 to trigger 5 AbortCheck events per second.
Args are passed using Chilkat.AbortCheckEventArgs
Event callback implementation:
Dim WithEvents compression As Chilkat.Compression Private Sub compression_OnAbortCheck(sender As Object, args As Chilkat.AbortCheckEventArgs) Handles compression.OnAbortCheck ... End Sub
PercentDone
This provides the percentage completion for any method involving network communications or time-consuming processing, assuming the progress can be measured as a percentage. This event is triggered only when it's possible and logical to express the operation's progress as a percentage. The pctDone argument will range from 1 to 100. For methods that finish quickly, the number of PercentDone callbacks may vary, but the final callback will have pctDone equal to 100. For longer operations, callbacks will not exceed one per percentage point (e.g., 1, 2, 3, ..., 98, 99, 100).
The PercentDone callback also acts as an AbortCheck
event. For fast methods where PercentDone fires, an AbortCheck event may not trigger since the PercentDone callback already provides an opportunity to abort. For longer operations, where time between PercentDone callbacks is extended, AbortCheck callbacks enable more responsive operation termination.
To abort the operation, set the abort output argument to True
. This will cause the method to terminate and return a failure status or corresponding failure value.
Args are passed using Chilkat.PercentDoneEventArgs
Event callback implementation:
Dim WithEvents compression As Chilkat.Compression Private Sub compression_OnPercentDone(sender As Object, args As Chilkat.PercentDoneEventArgs) Handles compression.OnPercentDone ... End Sub
ProgressInfo
This event callback provides tag name
/value pairs that detail what occurs during a method call. To discover existing tag names, create code to handle the event, emit the pairs, and review them. Most tag names are self-explanatory.
Args are passed using Chilkat.ProgressInfoEventArgs
Event callback implementation:
Dim WithEvents compression As Chilkat.Compression Private Sub compression_OnProgressInfo(sender As Object, args As Chilkat.ProgressInfoEventArgs) Handles compression.OnProgressInfo ... End Sub
TaskCompleted
Called from the background thread when an asynchronous task completes.
Args are passed using Chilkat.TaskCompletedEventArgs
Event callback implementation:
Dim WithEvents compression As Chilkat.Compression Private Sub compression_OnTaskCompleted(sender As Object, args As Chilkat.TaskCompletedEventArgs) Handles compression.OnTaskCompleted ... End Sub
Deprecated
BeginCompressBytes
The Begin*
, More*
, and End*
methods are replaced with the FirstChunk
and LastChunk
properties used in combination with FirstChunk/LastChunk aware
methods, such as CompressStr
and DecompressBd2
.
Large amounts of binary byte data may be compressed in chunks by first calling BeginCompressBytes, followed by 0 or more calls to MoreCompressedBytes, and ending with a final call to EndCompressBytes. Each call returns 0 or more bytes of compressed data which may be output to a compressed data stream (such as a file, socket, etc.).
Returns an empty byte array on failure
BeginCompressBytesENC
The Begin*
, More*
, and End*
methods are replaced with the FirstChunk
and LastChunk
properties used in combination with FirstChunk/LastChunk aware
methods, such as CompressStr
and DecompressBd2
.
Large amounts of binary byte data may be compressed in chunks by first calling BeginCompressBytesENC, followed by 0 or more calls to MoreCompressedBytesENC, and ending with a final call to EndCompressBytesENC. Each call returns 0 or more characters of compressed data (encoded as a string according to the EncodingMode property setting) which may be output to a compressed data stream (such as a file, socket, etc.).
Returns Nothing
on failure
BeginCompressString
The Begin*
, More*
, and End*
methods are replaced with the FirstChunk
and LastChunk
properties used in combination with FirstChunk/LastChunk aware
methods, such as CompressStr
and DecompressBd2
.
Large amounts of string data may be compressed in chunks by first calling BeginCompressString, followed by 0 or more calls to MoreCompressedString, and ending with a final call to EndCompressString. Each call returns 0 or more bytes of compressed data which may be output to a compressed data stream (such as a file, socket, etc.).
Returns an empty byte array on failure
BeginCompressStringENC
The Begin*
, More*
, and End*
methods are replaced with the FirstChunk
and LastChunk
properties used in combination with FirstChunk/LastChunk aware
methods, such as CompressStr
and DecompressBd2
.
Large amounts of string data may be compressed in chunks by first calling BeginCompressStringENC, followed by 0 or more calls to MoreCompressedStringENC, and ending with a final call to EndCompressStringENC. Each call returns 0 or more characters of compressed data (encoded as a string according to the EncodingMode property setting) which may be output to a compressed data stream (such as a file, socket, etc.).
Returns Nothing
on failure
BeginDecompressBytes
The Begin*
, More*
, and End*
methods are replaced with the FirstChunk
and LastChunk
properties used in combination with FirstChunk/LastChunk aware
methods, such as CompressStr
and DecompressBd2
.
A compressed data stream may be decompressed in chunks by first calling BeginDecompressBytes, followed by 0 or more calls to MoreDecompressedBytes, and ending with a final call to EndDecompressBytes. Each call returns 0 or more bytes of decompressed data.
Returns an empty byte array on failure
BeginDecompressBytesENC
The Begin*
, More*
, and End*
methods are replaced with the FirstChunk
and LastChunk
properties used in combination with FirstChunk/LastChunk aware
methods, such as CompressStr
and DecompressBd2
.
The input to this method is an encoded string containing compressed data. The EncodingMode property should be set prior to calling this method. The input string is decoded according to the EncodingMode (hex, base64, etc.) and then decompressed.
A compressed data stream may be decompressed in chunks by first calling BeginDecompressBytesENC, followed by 0 or more calls to MoreDecompressedBytesENC, and ending with a final call to EndDecompressBytesENC. Each call returns 0 or more bytes of decompressed data.
Returns an empty byte array on failure
topBeginDecompressString
The Begin*
, More*
, and End*
methods are replaced with the FirstChunk
and LastChunk
properties used in combination with FirstChunk/LastChunk aware
methods, such as CompressStr
and DecompressBd2
.
A compressed data stream may be decompressed in chunks by first calling BeginDecompressString, followed by 0 or more calls to MoreDecompressedString, and ending with a final call to EndDecompressString. Each call returns 0 or more characters of decompressed text.
Returns Nothing
on failure
BeginDecompressStringENC
The Begin*
, More*
, and End*
methods are replaced with the FirstChunk
and LastChunk
properties used in combination with FirstChunk/LastChunk aware
methods, such as CompressStr
and DecompressBd2
.
The input to this method is an encoded string containing compressed data. The EncodingMode property should be set prior to calling this method. The input string is decoded according to the EncodingMode (hex, base64, etc.) and then decompressed.
A compressed data stream may be decompressed in chunks by first calling BeginDecompressStringENC, followed by 0 or more calls to MoreDecompressedStringENC, and ending with a final call to EndDecompressStringENC. Each call returns 0 or more characters of decompressed text.
Returns Nothing
on failure
EndCompressBytes
The Begin*
, More*
, and End*
methods are replaced with the FirstChunk
and LastChunk
properties used in combination with FirstChunk/LastChunk aware
methods, such as CompressStr
and DecompressBd2
.
Must be callled to finalize a compression stream. Returns any remaining (buffered) compressed data.
(See BeginCompressBytes)
Returns an empty byte array on failure
EndCompressBytesENC
The Begin*
, More*
, and End*
methods are replaced with the FirstChunk
and LastChunk
properties used in combination with FirstChunk/LastChunk aware
methods, such as CompressStr
and DecompressBd2
.
Must be callled to finalize a compression stream. Returns any remaining (buffered) compressed data.
(See BeginCompressBytesENC)
Returns Nothing
on failure
EndCompressString
The Begin*
, More*
, and End*
methods are replaced with the FirstChunk
and LastChunk
properties used in combination with FirstChunk/LastChunk aware
methods, such as CompressStr
and DecompressBd2
.
Must be callled to finalize a compression stream. Returns any remaining (buffered) compressed data.
(See BeginCompressString)
Returns an empty byte array on failure
EndCompressStringENC
The Begin*
, More*
, and End*
methods are replaced with the FirstChunk
and LastChunk
properties used in combination with FirstChunk/LastChunk aware
methods, such as CompressStr
and DecompressBd2
.
Must be callled to finalize a compression stream. Returns any remaining (buffered) compressed data.
(See BeginCompressStringENC)
Returns Nothing
on failure
EndDecompressBytes
The Begin*
, More*
, and End*
methods are replaced with the FirstChunk
and LastChunk
properties used in combination with FirstChunk/LastChunk aware
methods, such as CompressStr
and DecompressBd2
.
Called to finalize the decompression stream and return any remaining (buffered) decompressed data.
(See BeginDecompressBytes)
Returns an empty byte array on failure
EndDecompressBytesENC
The Begin*
, More*
, and End*
methods are replaced with the FirstChunk
and LastChunk
properties used in combination with FirstChunk/LastChunk aware
methods, such as CompressStr
and DecompressBd2
.
Called to finalize the decompression stream and return any remaining (buffered) decompressed data.
The input to this method is an encoded string containing compressed data. The EncodingMode property should be set prior to calling this method. The input string is decoded according to the EncodingMode (hex, base64, etc.) and then decompressed.
(See BeginDecompressBytesENC)
Returns an empty byte array on failure
topEndDecompressString
The Begin*
, More*
, and End*
methods are replaced with the FirstChunk
and LastChunk
properties used in combination with FirstChunk/LastChunk aware
methods, such as CompressStr
and DecompressBd2
.
Called to finalize the decompression stream and return any remaining (buffered) decompressed data.
(See BeginDecompressString)
Returns Nothing
on failure
EndDecompressStringENC
The Begin*
, More*
, and End*
methods are replaced with the FirstChunk
and LastChunk
properties used in combination with FirstChunk/LastChunk aware
methods, such as CompressStr
and DecompressBd2
.
Called to finalize the decompression stream and return any remaining (buffered) decompressed data.
The input to this method is an encoded string containing compressed data. The EncodingMode property should be set prior to calling this method. The input string is decoded according to the EncodingMode (hex, base64, etc.) and then decompressed.
(See BeginDecompressStringENC)
Returns Nothing
on failure
MoreCompressBytes
MoreCompressBytesENC
MoreCompressString
MoreCompressStringENC
MoreDecompressBytes
MoreDecompressBytesENC
The input to this method is an encoded string containing compressed data. The EncodingMode property should be set prior to calling this method. The input string is decoded according to the EncodingMode (hex, base64, etc.) and then decompressed.
(See BeginDecompressBytesENC)
Returns an empty byte array on failure
topMoreDecompressString
MoreDecompressStringENC
The input to this method is an encoded string containing compressed data. The EncodingMode property should be set prior to calling this method. The input string is decoded according to the EncodingMode (hex, base64, etc.) and then decompressed.
(See BeginDecompressStringENC)
Returns Nothing
on failure