ZipCrc VB.NET Reference Documentation

ZipCrc

Current Version: 11.1.0

Calculate a Zip CRC checksum for a file or in-memory data.

Object Creation

Dim obj As New Chilkat.ZipCrc()

Properties

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
top
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.

top
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.

top
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.

top
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.

top
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.

top
Version
Version As String (ReadOnly)

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

More Information and Examples
top

Methods

BeginStream
Sub BeginStream()

Provides a way to calculate a CRC by streaming the data a chunk at a time. An application would start by calling BeginStream. Then it would add data by calling MoreData for each additional chunk. After the last chunk has been processed, the EndStream method is called to return the CRC.

top
CalculateCrc
Function CalculateCrc(ByVal data As Byte()) As UInteger

Calculates a 32-bit CRC for in-memory byte data. This is the 32-bit CRC that would be found in a Zip file header if a file containing the data was added to a zip archive. Returns the CRC32 of the data.

top
CrcBd
Function CrcBd(ByVal bd As BinData) As UInteger
Introduced in version 9.5.0.75

Calculates a CRC32 for the bytes contained in bd.

top
CrcSb
Function CrcSb(ByVal sb As StringBuilder, ByVal charset As String) As UInteger
Introduced in version 9.5.0.75

Calculates a CRC32 for the string contained in sb. The charset is the byte representation to be used for the sb when calculating the CRC32. It can be utf-8, utf-16, windows-1252, iso-8859-1, or any of the character encodings (charsets) listed at the link below.

top
CrcString
Function CrcString(ByVal str As String, ByVal charset As String) As UInteger
Introduced in version 9.5.0.75

Calculates a CRC32 for a string. The charset is the byte representation to be used for the str when calculating the CRC32. It can be utf-8, utf-16, windows-1252, iso-8859-1, or any of the character encodings (charsets) listed at the link below.

top
EndStream
Function EndStream() As UInteger

Finalizes and returns the Zip CRC value calculated by calling BeginStream followed by multiple calls to MoreData.

top
FileCrc
Function FileCrc(ByVal path As String) As UInteger

Calculates the CRC32 of a file. The data contained in the file is streamed for the calculation to keep the memory footprint small and constant. Returns the CRC32 of the file.

More Information and Examples
top
FileCrcAsync (1)
Function FileCrcAsync(ByVal path As String) As Task

Creates an asynchronous task to call the FileCrc 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

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

Loads the caller of the task's async method.

Returns True for success, False for failure.

top
MoreData
Sub MoreData(ByVal data As Byte())

Adds additional data to the CRC currently being calculated. (See BeginStream for more information.)

top
ToHex
Function ToHex(ByVal crc As UInteger) As String

Converts a 32-bit integer to a hex string.

Returns Nothing on failure

top

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 zipcrc As Chilkat.ZipCrc

Private Sub zipcrc_OnAbortCheck(sender As Object, args As Chilkat.AbortCheckEventArgs) Handles zipcrc.OnAbortCheck

    ...

End Sub
top
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 zipcrc As Chilkat.ZipCrc

Private Sub zipcrc_OnPercentDone(sender As Object, args As Chilkat.PercentDoneEventArgs) Handles zipcrc.OnPercentDone

    ...

End Sub
top
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.

More Information and Examples

Args are passed using Chilkat.ProgressInfoEventArgs

Event callback implementation:

Dim WithEvents zipcrc As Chilkat.ZipCrc

Private Sub zipcrc_OnProgressInfo(sender As Object, args As Chilkat.ProgressInfoEventArgs) Handles zipcrc.OnProgressInfo

    ...

End Sub
top
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 zipcrc As Chilkat.ZipCrc

Private Sub zipcrc_OnTaskCompleted(sender As Object, args As Chilkat.TaskCompletedEventArgs) Handles zipcrc.OnTaskCompleted

    ...

End Sub
top