Gzip VB.NET Reference Documentation

Gzip

GZip compression component.

Object Creation

Dim obj As New Chilkat.Gzip()

Properties

AbortCurrent As Boolean

Introduced in version 9.5.0.58

When set to True, causes the currently running method to abort. Methods that always finish quickly (i.e.have no length file operations or network communications) are not affected. If no method is running, then this property is automatically reset to False when the next method is called. When the abort occurs, this property is reset to False. Both synchronous and asynchronous method calls can be aborted. (A synchronous method call could be aborted by setting this property from a separate thread.)

Comment As String

Specifies an optional comment string that can be embedded within the .gz when any Compress* method is called.

CompressionLevel As Integer

Introduced in version 9.5.0.50

The compression level to be used when compressing. The default is 6, which is the typical value used for zip utility programs when compressing data. The compression level may range from 0 (no compression) to 9 (the most compression). The benefits of trying to increase compression may not be worth the added expense in compression time. In many cases (which is data dependent), the improvement in compression is minimal while the increase in computation time is significant.

DebugLogFilePath As String

If set to a file path, causes each Chilkat method or property call to automatically append it's LastErrorText to the specified log file. The information is appended such that if a hang or crash occurs, it is possible to see the context in which the problem occurred, as well as a history of all Chilkat calls up to the point of the problem. The VerboseLogging property can be set to provide more detailed information.

This property is typically used for debugging the rare cases where a Chilkat method call hangs or generates an exception that halts program execution (i.e. crashes). A hang or crash should generally never happen. The typical causes of a hang are:

  1. a timeout related property was set to 0 to explicitly indicate that an infinite timeout is desired,
  2. the hang is actually a hang within an event callback (i.e. it is a hang within the application code), or
  3. there is an internal problem (bug) in the Chilkat code that causes the hang.

ExtraData As Byte()

Optional extra-data that can be included within a .gz when a Compress* method is called.

Filename As String

The filename that is embedded within the .gz during any Compress* method call. When extracting from a .gz using applications such as WinZip, this will be the filename that is created.

HeartbeatMs As Integer

The number of milliseconds between each AbortCheck event callback. The AbortCheck callback allows an application to abort any method call prior to completion. If HeartbeatMs is 0 (the default), no AbortCheck event callbacks will fire.

LastErrorHtml As String (ReadOnly)

Provides information in HTML format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.

LastErrorText As String (ReadOnly)

Provides information in plain-text format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.

Concept of LastErrorText

LastErrorText Standard Information

LastErrorXml As String (ReadOnly)

Provides information in XML format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.

LastMethodSuccess As Boolean

Introduced in version 9.5.0.52

Indicate whether the last method call succeeded or failed. A value of True indicates success, a value of False indicates failure. This property is automatically set for method calls. It is not modified by property accesses. The property is automatically set to indicate success for the following types of method calls:

  • Any method that returns a string.
  • Any method returning a Chilkat object, binary bytes, or a date/time.
  • Any method returning a standard boolean status value where success = True and failure = False.
  • Any method returning an integer where failure is defined by a return value less than zero.

Note: Methods that do not fit the above requirements will always set this property equal to True. For example, a method that returns no value (such as a "void" in C++) will technically always succeed.

LastMod As Date

This property is deprecated. It will be removed in a future version.

The last-modification date/time to be embedded within the .gz when a Compress* method is called. By default, the current system date/time is used.

LastModStr As String

The same as the LastMod property, but allows the date/time to be get/set in RFC822 string format.

UseCurrentDate As Boolean

If set to True, the file produced by an Uncompress* method will use the current date/time for the last-modification date instead of the date/time found within the Gzip format.

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.

Version As String (ReadOnly)

Version of the component/library, such as "9.5.0.63"

Methods

Function CompressBd(ByVal binDat As BinData) As Boolean

Introduced in version 9.5.0.67

In-place gzip the contents of binDat.

Returns True for success, False for failure.

Gzip Compress In Memory and Base64 Encode

Function CompressBdAsync(ByVal binDat As BinData) As Task

Introduced in version 9.5.0.67

Creates an asynchronous task to call the CompressBd method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

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

How to Run an Asynchronous Task

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

Compresses a file to create a GZip compressed file (.gz).

Returns True for success, False for failure.

Function CompressFileAsync(ByVal inFilename As String, ByVal destPath As String) As Task

Creates an asynchronous task to call the CompressFile method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

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

How to Run an Asynchronous Task

Function CompressFile2(ByVal inFilename As String, ByVal embeddedFilename As String, ByVal destPath As String) As Boolean

Compresses a file to create a GZip compressed file (.gz). inFilename is the actual filename on disk. embeddedFilename is the filename to be embedded in the .gz such that when it is un-gzipped, this is the name of the file that will be created.

Returns True for success, False for failure.

Function CompressFile2Async(ByVal inFilename As String, ByVal embeddedFilename As String, ByVal destPath As String) As Task

Creates an asynchronous task to call the CompressFile2 method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

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

How to Run an Asynchronous Task

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

Gzip compresses a file to an in-memory image of a .gz file.

Returns an empty byte array on failure

Function CompressFileToMemAsync(ByVal inFilename As String) As Task

Creates an asynchronous task to call the CompressFileToMem method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

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

How to Run an Asynchronous Task

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

Compresses in-memory data to an in-memory image of a .gz file.

Returns an empty byte array on failure

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

Creates an asynchronous task to call the CompressMemory method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

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

How to Run an Asynchronous Task

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

Gzip compresses and creates a .gz file from in-memory data.

Returns True for success, False for failure.

Function CompressMemToFileAsync(ByVal inData As Byte(), ByVal destPath As String) As Task

Creates an asynchronous task to call the CompressMemToFile method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

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

How to Run an Asynchronous Task

Function CompressString(ByVal inStr As String, ByVal destCharset As String) As Byte()

Gzip compresses a string and writes the output to a byte array. The string is first converted to the charset specified by destCharset. Typical charsets are "utf-8", "iso-8859-1", "shift_JIS", etc.

Returns an empty byte array on failure

Full List of Charset Names

Function CompressStringAsync(ByVal inStr As String, ByVal destCharset As String) As Task

Creates an asynchronous task to call the CompressString method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

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

How to Run an Asynchronous Task

Function CompressStringENC(ByVal inStr As String, ByVal charset As String, ByVal encoding As String) As String

The same as CompressString, except the binary output is returned in encoded string form according to the encoding. The encoding can be any of the following: "Base64", "modBase64", "Base32", "UU", "QP" (for quoted-printable), "URL" (for url-encoding), "Hex", "Q", "B", "url_oath", "url_rfc1738", "url_rfc2396", and "url_rfc3986".

Returns Nothing on failure

Function CompressStringToFile(ByVal inStr As String, ByVal destCharset As String, ByVal destPath As String) As Boolean

Gzip compresses a string and writes the output to a .gz compressed file. The string is first converted to the charset specified by destCharset. Typical charsets are "utf-8", "iso-8859-1", "shift_JIS", etc.

Returns True for success, False for failure.

Full List of Charset Names

Function CompressStringToFileAsync(ByVal inStr As String, ByVal destCharset As String, ByVal destPath As String) As Task

Creates an asynchronous task to call the CompressStringToFile method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

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

How to Run an Asynchronous Task

Function Decode(ByVal encodedStr As String, ByVal encoding As String) As Byte()

Decodes an encoded string and returns the original data. The encoding mode is determined by encoding. It may be "base64", "hex", "quoted-printable", or "url".

Returns an empty byte array on failure

Function DeflateStringENC(ByVal inString As String, ByVal charsetName As String, ByVal outputEncoding As String) As String

Provides the ability to use the zip/gzip's deflate algorithm directly to compress a string. Internal to this method, inString is first converted to the charset specified by charsetName. The data is then compressed using the deflate compression algorithm. The binary output is then encoded according to outputEncoding. Possible values for outputEncoding are "hex", "base64", "url", and "quoted-printable".

Note: The output of this method is compressed data with no Gzip file format. Use the Compress* methods to produce Gzip file format output.

Returns Nothing on failure

Full List of Charset Names

Function Encode(ByVal byteData As Byte(), ByVal encoding As String) As String

Encodes binary data to a printable string. The encoding mode is determined by encoding. It may be "base64", "hex", "quoted-printable", or "url".

Returns Nothing on failure

Function ExamineFile(ByVal inGzFilename As String) As Boolean

Determines if the inGzFilename is a Gzip formatted file. Returns True if it is a Gzip formatted file, otherwise returns False.

Function ExamineMemory(ByVal inGzData As Byte()) As Boolean

Determines if the in-memory bytes (inGzData) contain a Gzip formatted file. Returns True if it is Gzip format, otherwise returns False.

Function GetDt() As CkDateTime

Gets the last-modification date/time to be embedded within the .gz.

Returns Nothing on failure

Function InflateStringENC(ByVal inString As String, ByVal convertFromCharset As String, ByVal inputEncoding As String) As String

This the reverse of DeflateStringENC.

The input string is first decoded according to inputEncoding. (Possible values for inputEncoding are "hex", "base64", "url", and "quoted-printable".) The compressed data is then inflated, and the result is then converted from convertFromCharset (if necessary) to return a string.

Returns Nothing on failure

Function IsUnlocked() As Boolean

Returns True if the component has been unlocked.

Function ReadFile(ByVal path As String) As Byte()

Reads a binary file into memory and returns the byte array. Note: This method does not parse a Gzip, it is only a convenience method for reading a binary file into memory.

Returns an empty byte array on failure

Function SaveLastError(ByVal path As String) As Boolean

Saves the last-error information (the contents of LastErrorXml) to an XML formatted file.

Returns True for success, False for failure.

Function SetDt(ByVal dt As CkDateTime) As Boolean

Sets the last-modification date/time to be embedded within the .gz when a Compress* method is called. If not explicitly set, the current system date/time is used.

Returns True for success, False for failure.

Function UncompressBd(ByVal binDat As BinData) As Boolean

Introduced in version 9.5.0.67

In-place ungzip the contents of binDat.

Returns True for success, False for failure.

Function UncompressBdAsync(ByVal binDat As BinData) As Task

Introduced in version 9.5.0.67

Creates an asynchronous task to call the UncompressBd method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

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

How to Run an Asynchronous Task

Function UncompressFile(ByVal srcPath As String, ByVal destPath As String) As Boolean

Un-Gzips a .gz file. The output filename is specified by the 2nd argument and not by the filename embedded within the .gz.

Returns True for success, False for failure.

GZip Decompress File

Function UncompressFileAsync(ByVal srcPath As String, ByVal destPath As String) As Task

Creates an asynchronous task to call the UncompressFile method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

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

How to Run an Asynchronous Task

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

Un-Gzips a .gz file directly to memory.

Returns an empty byte array on failure

Function UncompressFileToMemAsync(ByVal inFilename As String) As Task

Creates an asynchronous task to call the UncompressFileToMem method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

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

How to Run an Asynchronous Task

Function UncompressFileToString(ByVal gzFilename As String, ByVal charset As String) As String

Uncompresses a .gz file that contains a text file. The contents of the text file are returned as a string. The character encoding of the text file is specified by charset. Typical charsets are "iso-8859-1", "utf-8", "windows-1252", "shift_JIS", "big5", etc.

Returns Nothing on failure

List of Valid Charsets

Function UncompressFileToStringAsync(ByVal gzFilename As String, ByVal charset As String) As Task

Creates an asynchronous task to call the UncompressFileToString method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

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

How to Run an Asynchronous Task

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

Un-Gzips from an in-memory image of a .gz file directly into memory.

Returns an empty byte array on failure

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

Creates an asynchronous task to call the UncompressMemory method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

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

How to Run an Asynchronous Task

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

Un-Gzips from an in-memory image of a .gz file to a file.

Returns True for success, False for failure.

Function UncompressMemToFileAsync(ByVal inData As Byte(), ByVal destPath As String) As Task

Creates an asynchronous task to call the UncompressMemToFile method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

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

How to Run an Asynchronous Task

Function UncompressString(ByVal inData As Byte(), ByVal inCharset As String) As String

The reverse of CompressString.

The bytes in inData are uncompressed, then converted from inCharset (if necessary) to return a string.

Returns Nothing on failure

Full List of Charset Names

Function UncompressStringAsync(ByVal inData As Byte(), ByVal inCharset As String) As Task

Creates an asynchronous task to call the UncompressString method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

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

How to Run an Asynchronous Task

Function UncompressStringENC(ByVal inStr As String, ByVal charset As String, ByVal encoding As String) As String

The same as UncompressString, except the compressed data is provided in encoded string form based on the value of encoding. The encoding can be "Base64", "modBase64", "Base32", "UU", "QP" (for quoted-printable), "URL" (for url-encoding), "Hex", "Q", "B", "url_oath", "url_rfc1738", "url_rfc2396", and "url_rfc3986".

Returns Nothing on failure

Function UnlockComponent(ByVal unlockCode As String) As Boolean

Unlocks the component allowing for the full functionality to be used.

Returns True for success, False for failure.

Diagnosing UnlockComponent Problems

UnlockComponent LastErrorText shows exact string passed to it.

Verify UnlockComponent Success w/ Purchased Unlock Code

LastErrorText Standard Information

Function UnTarGz(ByVal tgzFilename As String, ByVal destDir As String, ByVal bNoAbsolute As Boolean) As Boolean

Unpacks a .tar.gz file. The ungzip and untar occur in streaming mode. There are no temporary files and the memory footprint is constant (and small) while untarring. bNoAbsolute may be True or False. A value of True protects from untarring to absolute paths. (For example, imagine the trouble if the tar contains files with absolute paths beginning with /Windows/system32)

Returns True for success, False for failure.

Function UnTarGzAsync(ByVal tgzFilename As String, ByVal destDir As String, ByVal bNoAbsolute As Boolean) As Task

Creates an asynchronous task to call the UnTarGz method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

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

How to Run an Asynchronous Task

Function WriteFile(ByVal path As String, ByVal binaryData As Byte()) As Boolean

A convenience method for writing a binary byte array to a file.

Returns True for success, False for failure.

Function XfdlToXml(ByVal xfldData As String) As String

Converts base64-gzip .xfdl data to a decompressed XML string. The xfldData contains the base64 data. This method returns the decoded/decompressed XML string.

Returns Nothing on failure

Events

Event OnAbortCheck

Provides the opportunity for a method call to be aborted. The AbortCheck event is fired periodically based on the value of the HeartbeatMs property. If HeartbeatMs is 0, then no AbortCheck events will fire. As an example, to fire 5 AbortCheck events per second, set the HeartbeatMs property equal to 200.

Args are passed using Chilkat.AbortCheckEventArgs

Event callback implementation:

Dim WithEvents gzip As Chilkat.Gzip

Private Sub gzip_OnAbortCheck(sender As Object, args As Chilkat.AbortCheckEventArgs) Handles gzip.OnAbortCheck

    ...

End Sub

Event OnBinaryData

Binary data provided by certain methods.

Args are passed using Chilkat.BinaryDataEventArgs

Event callback implementation:

Dim WithEvents gzip As Chilkat.Gzip

Private Sub gzip_OnBinaryData(sender As Object, args As Chilkat.BinaryDataEventArgs) Handles gzip.OnBinaryData

    ...

End Sub

Event OnPercentDone

Provides the percentage completed for any method that involves network communications or time-consuming processing (assuming it is a method where a percentage completion can be measured). This event is only fired when it is possible to know a percentage completion, and when it makes sense to express the operation as a percentage completed. The pctDone argument will have a value from 1 to 100. For operations (Chilkat method calls) that complete very quickly, the number of PercentDone callbacks will vary, but the final callback should have a value of 100. For long running operations, no more than one callback per percentage point will occur (for example: 1, 2, 3, ... 98, 99, 100).

The PercentDone callback counts as an AbortCheck event. For method calls that complete quickly such that PercentDone events fire, it may be that AbortCheck events don't fire because the opportunity to abort is already provided in the PercentDone callback. For time consuming operations, where the amount of time between PercentDone callbacks are long, AbortCheck callbacks may be used to allow for the operation to be aborted in a more responsive manner.

The abort output argument provides a means for aborting the operation. Setting it to True will cause the method to abort and return a failed status (or whatever return value indicates failure).

Args are passed using Chilkat.PercentDoneEventArgs

Event callback implementation:

Dim WithEvents gzip As Chilkat.Gzip

Private Sub gzip_OnPercentDone(sender As Object, args As Chilkat.PercentDoneEventArgs) Handles gzip.OnPercentDone

    ...

End Sub

Event OnProgressInfo

A general name/value event that provides information about what is happening during a method call. To find out what information is available, write code to handle this event and log the name/value pairs. Most are self-explanatory.

Args are passed using Chilkat.ProgressInfoEventArgs

Event callback implementation:

Dim WithEvents gzip As Chilkat.Gzip

Private Sub gzip_OnProgressInfo(sender As Object, args As Chilkat.ProgressInfoEventArgs) Handles gzip.OnProgressInfo

    ...

End Sub

Event OnTaskCompleted

Called in the background thread when an asynchronous task completes.

VB.NET TaskCompleted Event Callback Example

Args are passed using Chilkat.TaskCompletedEventArgs

Event callback implementation:

Dim WithEvents gzip As Chilkat.Gzip

Private Sub gzip_OnTaskCompleted(sender As Object, args As Chilkat.TaskCompletedEventArgs) Handles gzip.OnTaskCompleted

    ...

End Sub

Event OnTextData

Text data provided by certain methods.

Args are passed using Chilkat.TextDataEventArgs

Event callback implementation:

Dim WithEvents gzip As Chilkat.Gzip

Private Sub gzip_OnTextData(sender As Object, args As Chilkat.TextDataEventArgs) Handles gzip.OnTextData

    ...

End Sub