Bz2 VB.NET Reference Documentation

Bz2

Current Version: 11.5.0

Chilkat.Bz2 provides BZip2 compression and decompression for files, memory buffers, and BinData. It can create standard .bz2 file images, decompress .bz2 content back to its original bytes, and support abortable long-running operations.

For an extended overview, see Bz2 Class Overview

Object Creation

Dim obj As New Chilkat.Bz2()

Properties

AbortCurrent
AbortCurrent As Boolean
Introduced in version 9.5.0.58

Set this property to True to request cancellation of the compression or decompression operation currently executing on this object. Long-running operations check the request periodically; an operation that finishes quickly may complete before the request is observed.

A synchronous call can be cancelled by setting this property from another thread. After cancellation is processed, Chilkat resets the property to False. If no operation is running, a previously set value is cleared when the next method begins.

Cancellation is cooperative: Setting this property requests an abort; it does not guarantee immediate termination. Check the method's return value and LastErrorText to determine the final outcome.

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DebugLogFilePath
DebugLogFilePath As String

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.

More Information and Examples
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HeartbeatMs
HeartbeatMs As Integer

Specifies the interval, in milliseconds, between AbortCheck event callbacks during supported long-running compression and decompression operations. The default is 0, which disables AbortCheck callbacks.

Set a positive value, such as 200, when the application needs periodic opportunities to request cancellation. The interval is approximate; callbacks occur only while an operation is at a point where progress events can be delivered.

Cancellation workflow: In an AbortCheck handler, set the callback's abort value to request termination. A synchronous method may also be cancelled from another thread by setting AbortCurrent to True.

More Information and Examples
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LastErrorHtml
LastErrorHtml As String (ReadOnly)

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.

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LastErrorText
LastErrorText As String (ReadOnly)

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.

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LastErrorXml
LastErrorXml As String (ReadOnly)

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.

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LastMethodSuccess
LastMethodSuccess As Boolean

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. Note: This property does not apply to methods that return integer values or to boolean-returning methods where the boolean does not indicate success or failure.

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VerboseLogging
VerboseLogging As Boolean

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.

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Version
Version As String (ReadOnly)

Version of the component/library, such as "10.1.0"

More Information and Examples
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Methods

CompressBd
Function CompressBd(ByVal bd As BinData) As Boolean
Introduced in version 11.0.0

Compresses the current contents of bd in place. On success, the BinData no longer contains the original bytes; it contains the complete standard BZip2 stream that may be saved with a .bz2 extension.

In-place transformation: Preserve a copy of the original data if it is still needed after this call. A BZip2 stream contains a stream header, one or more compressed blocks with integrity checks, and an end-of-stream marker. It does not contain archive filenames or directory entries.

Returns True for success, False for failure.

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CompressBdAsync (1)
Function CompressBdAsync(ByVal bd As BinData) As Task
Introduced in version 11.0.0

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

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CompressFile
Function CompressFile(ByVal inFilename As String, ByVal toPath As String) As Boolean

Reads the file at inFilename and writes its compressed bytes as a standard BZip2 stream to the file at toPath. The output is conventionally given a .bz2 extension.

Both arguments must identify files, not directories. They may be absolute or relative paths, for example data/report.txt and data/report.txt.bz2.

BZip2 is a compressor, not an archive format: A .bz2 file represents one compressed byte stream. It does not store the original filename, directory path, timestamps, permissions, or multiple archive entries. Formats such as .tar.bz2 first combine files in a TAR archive and then compress that TAR stream with BZip2.

Returns True for success, False for failure.

More Information and Examples
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CompressFileAsync (1)
Function CompressFileAsync(ByVal inFilename As String, ByVal toPath As String) As Task

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

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CompressFileToMem
Function CompressFileToMem(ByVal inFilename As String) As Byte()

Reads the file at inFilename, compresses it with BZip2, and returns the complete .bz2 byte stream in memory.

Returns an empty byte array on failure

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CompressFileToMemAsync (1)
Function CompressFileToMemAsync(ByVal inFilename As String) As Task

Creates an asynchronous task to call the CompressFileToMem 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

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CompressMemory
Function CompressMemory(ByVal inData As Byte()) As Byte()

Compresses the bytes in inData and returns the complete standard BZip2 stream as an in-memory byte array.

Returns an empty byte array on failure

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CompressMemoryAsync (1)
Function CompressMemoryAsync(ByVal inData As Byte()) As Task

Creates an asynchronous task to call the CompressMemory 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

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CompressMemToFile
Function CompressMemToFile(ByVal inData As Byte(), ByVal toPath As String) As Boolean

Compresses the bytes in inData and writes the resulting standard BZip2 stream to the file at toPath.

Returns True for success, False for failure.

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CompressMemToFileAsync (1)
Function CompressMemToFileAsync(ByVal inData As Byte(), ByVal toPath As String) As Task

Creates an asynchronous task to call the CompressMemToFile 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

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LoadTaskCaller
Function LoadTaskCaller(ByVal task As Task) As Boolean
Introduced in version 9.5.0.80

Loads this Bz2 object with the caller state associated with the asynchronous operation represented by task.

Advanced async infrastructure: This method is used to recover the original caller object associated with a completed task. It is not normally needed by application code. Pass a Task created by a compatible Bz2 asynchronous method; an unrelated task cannot be loaded.

Returns True for success, False for failure.

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UncompressBd
Function UncompressBd(ByVal bd As BinData) As Boolean
Introduced in version 11.0.0

Decompresses the BZip2 stream currently contained in bd in place. On success, the BinData is replaced with the original uncompressed bytes.

Input requirement: bd must contain a complete, valid BZip2 stream, such as the bytes of a .bz2 file or the output of CompressBd. This method operates on binary data and does not perform character-set conversion.

Returns True for success, False for failure.

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UncompressBdAsync (1)
Function UncompressBdAsync(ByVal bd As BinData) As Task
Introduced in version 11.0.0

Creates an asynchronous task to call the UncompressBd 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

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UncompressFile
Function UncompressFile(ByVal inFilename As String, ByVal toPath As String) As Boolean

Reads the BZip2 stream from the file at inFilename, decompresses it, and writes the original uncompressed bytes to the file at toPath.

Both arguments must identify files, not directories. Chilkat does not derive the destination name from the .bz2 filename because the BZip2 stream does not contain the original filename.

Terminology: This method decompresses BZip2 data; it does not “unzip” a ZIP archive. A .bz2 file normally contains a single compressed byte stream rather than a collection of named files.

Returns True for success, False for failure.

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UncompressFileAsync (1)
Function UncompressFileAsync(ByVal inFilename As String, ByVal toPath As String) As Task

Creates an asynchronous task to call the UncompressFile 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

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UncompressFileToMem
Function UncompressFileToMem(ByVal inFilename As String) As Byte()

Reads and decompresses the BZip2 stream in the file at inFilename, returning the original uncompressed bytes in memory.

Returns an empty byte array on failure

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UncompressFileToMemAsync (1)
Function UncompressFileToMemAsync(ByVal inFilename As String) As Task

Creates an asynchronous task to call the UncompressFileToMem 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

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UncompressMemory
Function UncompressMemory(ByVal inData As Byte()) As Byte()

Interprets inData as a complete BZip2 stream and returns the decompressed bytes in memory.

Returns an empty byte array on failure

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UncompressMemoryAsync (1)
Function UncompressMemoryAsync(ByVal inData As Byte()) As Task

Creates an asynchronous task to call the UncompressMemory 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

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UncompressMemToFile
Function UncompressMemToFile(ByVal inData As Byte(), ByVal toPath As String) As Boolean

Interprets inData as a complete BZip2 stream, decompresses it, and writes the original bytes to the file at toPath.

Returns True for success, False for failure.

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UncompressMemToFileAsync (1)
Function UncompressMemToFileAsync(ByVal inData As Byte(), ByVal toPath As String) As Task

Creates an asynchronous task to call the UncompressMemToFile 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

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Events

AbortCheck
Event OnAbortCheck

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.

More Information and Examples

Args are passed using Chilkat.AbortCheckEventArgs

Event callback implementation:

Dim WithEvents bz As Chilkat.Bz2

Private Sub bz_OnAbortCheck(sender As Object, args As Chilkat.AbortCheckEventArgs) Handles bz.OnAbortCheck

    ...

End Sub
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PercentDone
Event OnPercentDone

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.

More Information and Examples

Args are passed using Chilkat.PercentDoneEventArgs

Event callback implementation:

Dim WithEvents bz As Chilkat.Bz2

Private Sub bz_OnPercentDone(sender As Object, args As Chilkat.PercentDoneEventArgs) Handles bz.OnPercentDone

    ...

End Sub
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ProgressInfo
Event OnProgressInfo

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.

Note: Some Chilkat methods don't fire any ProgressInfo events.

More Information and Examples

Args are passed using Chilkat.ProgressInfoEventArgs

Event callback implementation:

Dim WithEvents bz As Chilkat.Bz2

Private Sub bz_OnProgressInfo(sender As Object, args As Chilkat.ProgressInfoEventArgs) Handles bz.OnProgressInfo

    ...

End Sub
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TaskCompleted
Event OnTaskCompleted

Called from the background thread when an asynchronous task completes.

More Information and Examples

Args are passed using Chilkat.TaskCompletedEventArgs

Event callback implementation:

Dim WithEvents bz As Chilkat.Bz2

Private Sub bz_OnTaskCompleted(sender As Object, args As Chilkat.TaskCompletedEventArgs) Handles bz.OnTaskCompleted

    ...

End Sub
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