Gzip Xojo Plugin Reference Documentation

Gzip

Current Version: 11.4.0

Requires Chilkat Bundle License

This class provides functionality for working with GZIP compression in both file-based and in-memory scenarios. It supports compressing and decompressing:

Files (.gz, .tar.gz)
Strings (with charset conversion)
Binary data (byte[], BinData)
Encoded data (Base64, Hex, etc.)

It also allows embedding metadata such as filenames, timestamps, and comments within the GZIP format.

For an extended overview, see Gzip Class Overview.

Object Creation

Dim gzip As New Chilkat.Gzip

Properties

AbortCurrent

AbortCurrent As Boolean

Introduced in version 9.5.0.58

Set this property to True to request that the currently running operation be aborted. This is useful for long-running operations such as large file compression or decompression. Methods that complete quickly are generally not affected.

If no method is currently running, the property is automatically reset to False when the next method begins. After an abort occurs, it is also reset to False. Both synchronous and asynchronous operations can be aborted. For synchronous calls, another thread must set this property.

Comment

Comment As String

An optional comment to embed in the Gzip file when a Compress* method is called.

CompressionLevel

CompressionLevel As Int32

Introduced in version 9.5.0.50

Controls the compression level used when creating Gzip data. The value can range from 0 to 9.

0 = no compression
9 = maximum compression

The default value is 6, which is a typical balance between compression size and speed. Higher levels may take significantly more CPU time while producing only slightly smaller output, depending on the data.

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

Example showing how to use DebugLogFilePath.

Filename

Filename As String

The filename to embed in the Gzip file when a Compress* method is called. Some Gzip extraction tools use this embedded filename as the default output filename.

HeartbeatMs

HeartbeatMs As Int32

Specifies the interval, in milliseconds, between AbortCheck event callbacks. These callbacks allow an application to cancel certain long-running operations before they finish.

The default value is 0, which means no AbortCheck callbacks are triggered.

More Information and Examples

Event Callback Examples

LastErrorHtml

LastErrorHtml As String (read-only)

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.

LastErrorText

LastErrorText As String (read-only)

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.

More Information and Examples

Concept of LastErrorText LastErrorText Standard Information

LastErrorXml

LastErrorXml As String (read-only)

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.

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.

LastModStr

LastModStr As String

Specifies the last-modified date/time to embed in the Gzip file when a Compress* method is called.

The value must be provided as an RFC 822 formatted date/time string.

Example:

Tue, 15 Nov 1994 12:45:26 GMT

If this property is not set, the current system date/time is used automatically.

UseCurrentDate

UseCurrentDate As Boolean

Controls the last-modified date/time assigned to files created by Uncompress* methods.

When set to True, the extracted file uses the current date/time instead of the date/time stored in the Gzip data.

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.

Version

Version As String (read-only)

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

More Information and Examples

How to get the Chilkat version at runtime.

Methods

CompressBd

Function CompressBd(binDat As Chilkat.BinData) As Boolean

Introduced in version 9.5.0.67

Compresses the contents of a BinData object in place, replacing the original data with Gzip-compressed data.

Returns True for success, False for failure.

More Information and Examples

Gzip Compress In Memory and Base64 Encode

CompressBdAsync ⁽¹⁾

Function CompressBdAsync(binDat As Chilkat.BinData) As Chilkat.Task

Introduced in version 9.5.0.67

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 Nil on failure

CompressFile

Function CompressFile(srcPath As String, destPath As String) As Boolean

Compresses a file and writes the result as a Gzip file, typically with a .gz extension.

Returns True for success, False for failure.

More Information and Examples

CompressFileAsync ⁽¹⁾

Function CompressFileAsync(srcPath As String, destPath As String) As Chilkat.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 Nil on failure

CompressFile2

Function CompressFile2(srcPath As String, embeddedFilename As String, destPath As String) As Boolean

Compresses a file and writes the result as a Gzip file, while allowing a different filename to be embedded inside the Gzip data.

The inFilename parameter is the actual file on disk. The srcPath parameter is the filename stored in the Gzip header and may be used by extraction tools as the output filename.

Returns True for success, False for failure.

More Information and Examples

CompressFile2Async ⁽¹⁾

Function CompressFile2Async(srcPath As String, embeddedFilename As String, destPath As String) As Chilkat.Task

Creates an asynchronous task to call the CompressFile2 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 Nil on failure

CompressFileBd

Function CompressFileBd(filePath As String, bd As Chilkat.BinData) As Boolean

Introduced in version 11.0.0

Compresses a file and stores the resulting Gzip data in a BinData object.

The compressed output is held in memory. The maximum compressed size is 4 GB.

Returns True for success, False for failure.

More Information and Examples

Compress a File to Gzip in Memory using BinData

CompressFileBdAsync ⁽¹⁾

Function CompressFileBdAsync(filePath As String, bd As Chilkat.BinData) As Chilkat.Task

Introduced in version 11.0.0

Creates an asynchronous task to call the CompressFileBd 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 Nil on failure

CompressFileToMem

Function CompressFileToMem(inFilename As String) As MemoryBlock

Compresses a file and returns the resulting Gzip data as a byte array.

The compressed output is held in memory and has a maximum size limit of 4 GB.

Returns Nil on failure

CompressFileToMemAsync ⁽¹⁾

Function CompressFileToMemAsync(inFilename As String) As Chilkat.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 Nil on failure

CompressMemory

Function CompressMemory(inData As MemoryBlock) As MemoryBlock

Compresses a byte array and returns the result as an in-memory Gzip image.

The uncompressed input data must not exceed 4 GB.

Returns Nil on failure

CompressMemoryAsync ⁽¹⁾

Function CompressMemoryAsync(inData As MemoryBlock) As Chilkat.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 Nil on failure

CompressMemToFile

Function CompressMemToFile(inData As MemoryBlock, destPath As String) As Boolean

Compresses a byte array and writes the resulting Gzip data to a file.

Returns True for success, False for failure.

CompressMemToFileAsync ⁽¹⁾

Function CompressMemToFileAsync(inData As MemoryBlock, destPath As String) As Chilkat.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 Nil on failure

CompressSb

Function CompressSb(sb As Chilkat.StringBuilder, charset As String, bd As Chilkat.BinData) As Boolean

Introduced in version 11.0.0

Compresses the text contained in a StringBuilder and writes the Gzip-compressed result to a BinData object.

Before compression, the string is converted to bytes using the specified character set, such as utf-8, iso-8859-1, or shift_JIS.

Returns True for success, False for failure.

More Information and Examples

Compress Text from StringBuilder to Gzip (BinData Output)

CompressSbAsync ⁽¹⁾

Function CompressSbAsync(sb As Chilkat.StringBuilder, charset As String, bd As Chilkat.BinData) As Chilkat.Task

Introduced in version 11.0.0

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 Nil on failure

CompressString

Function CompressString(inStr As String, destCharset As String) As MemoryBlock

Compresses a string and returns the Gzip-compressed data as a byte array.

The string is first converted to bytes using the character set specified by destCharset. Common values include utf-8, iso-8859-1, and shift_JIS.

Returns Nil on failure

More Information and Examples

Full List of Charset Names

CompressStringAsync ⁽¹⁾

Function CompressStringAsync(inStr As String, destCharset As String) As Chilkat.Task

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 Nil on failure

CompressStringENC

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

Compresses a string and returns the Gzip-compressed data as an encoded string.

The input string is first converted to bytes using the specified character set. The compressed binary data is then encoded using the requested encoding, such as base64, hex, url, base32, or quoted-printable.

Returns Nil on failure

More Information and Examples

Compress a String to Gzip and Return as Base64 Binary Encodings Supported by Chilkat

CompressStringToFile

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

Compresses a string and writes the resulting Gzip data to a file.

The string is first converted to bytes using the character set specified by destCharset.

Returns True for success, False for failure.

More Information and Examples

Full List of Charset Names Compress a String and Save as a Gzip File

CompressStringToFileAsync ⁽¹⁾

Function CompressStringToFileAsync(inStr As String, destCharset As String, destPath As String) As Chilkat.Task

Creates an asynchronous task to call the CompressStringToFile 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 Nil on failure

ExamineFile

Function ExamineFile(filePath As String) As Boolean

Checks whether the specified file contains Gzip-formatted data.

Returns True if the file is in Gzip format, or False otherwise.

More Information and Examples

Check if a File is in Gzip Format

ExamineMemory

Function ExamineMemory(inGzData As MemoryBlock) As Boolean

Checks whether the provided byte array contains Gzip-formatted data.

Returns True if the data is in Gzip format, or False otherwise.

IsGzip

Function IsGzip(bd As Chilkat.BinData) As Boolean

Introduced in version 11.0.0

Checks whether the data contained in a BinData object is in Gzip format.

Returns True if the data is Gzip-formatted, or False otherwise.

LoadTaskCaller

Function LoadTaskCaller(task As Chilkat.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.

SetDt

Function SetDt(dt As Chilkat.CkDateTime) As Boolean

Sets the last-modified date/time to embed in the Gzip file when a Compress* method is called.

If no date/time is explicitly set, the current system date/time is used.

Returns True for success, False for failure.

More Information and Examples

Set a Custom Last-Modified Date in a Gzip File

SetExtraData

Function SetExtraData(encodedData As String, encoding As String) As Boolean

Introduced in version 11.0.0

Sets optional extra binary data to include in the Gzip header when a Compress* method is called.

The data is passed as an encoded string. Supported encodings include base64, hex, ascii, and many others.

Returns True for success, False for failure.

More Information and Examples

Binary Encodings Supported by Chilkat

UncompressBd

Function UncompressBd(binDat As Chilkat.BinData) As Boolean

Introduced in version 9.5.0.67

Decompresses Gzip data contained in a BinData object in place, replacing the compressed data with the uncompressed data.

Returns True for success, False for failure.

UncompressBdAsync ⁽¹⁾

Function UncompressBdAsync(binDat As Chilkat.BinData) As Chilkat.Task

Introduced in version 9.5.0.67

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 Nil on failure

UncompressBdToFile

Function UncompressBdToFile(bd As Chilkat.BinData, filePath As String) As Boolean

Introduced in version 11.0.0

Decompresses Gzip data stored in a BinData object and writes the result to a file.

Returns True for success, False for failure.

UncompressBdToFileAsync ⁽¹⁾

Function UncompressBdToFileAsync(bd As Chilkat.BinData, filePath As String) As Chilkat.Task

Introduced in version 11.0.0

Creates an asynchronous task to call the UncompressBdToFile 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 Nil on failure

UncompressFile

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

Decompresses a Gzip file and writes the result to the specified output path.

The output filename is provided by the caller. The filename embedded in the Gzip data is not used.

Returns True for success, False for failure.

More Information and Examples

GZip Decompress File

UncompressFileAsync ⁽¹⁾

Function UncompressFileAsync(srcPath As String, destPath As String) As Chilkat.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 Nil on failure

UncompressFileToMem

Function UncompressFileToMem(srcPath As String) As MemoryBlock

Decompresses a Gzip file and returns the uncompressed data as a byte array.

The uncompressed output is held in memory and must not exceed 4 GB.

Returns Nil on failure

UncompressFileToMemAsync ⁽¹⁾

Function UncompressFileToMemAsync(srcPath As String) As Chilkat.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 Nil on failure

UncompressFileToString

Function UncompressFileToString(srcPath As String, charset As String) As String

Decompresses a Gzip file that contains text and returns the uncompressed text as a string.

The charset parameter specifies the character encoding of the uncompressed text, such as utf-8, iso-8859-1, windows-1252, shift_JIS, big5, etc.

Returns Nil on failure

More Information and Examples

List of Valid Charsets

UncompressFileToStringAsync ⁽¹⁾

Function UncompressFileToStringAsync(srcPath As String, charset As String) As Chilkat.Task

Creates an asynchronous task to call the UncompressFileToString 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 Nil on failure

UncompressMemory

Function UncompressMemory(inData As MemoryBlock) As MemoryBlock

Decompresses an in-memory Gzip image and returns the uncompressed data as a byte array.

The uncompressed output is held in memory and must not exceed 4 GB.

Returns Nil on failure

UncompressMemoryAsync ⁽¹⁾

Function UncompressMemoryAsync(inData As MemoryBlock) As Chilkat.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 Nil on failure

UncompressMemToFile

Function UncompressMemToFile(inData As MemoryBlock, destPath As String) As Boolean

Decompresses an in-memory Gzip image and writes the uncompressed data to a file.

Returns True for success, False for failure.

UncompressMemToFileAsync ⁽¹⁾

Function UncompressMemToFileAsync(inData As MemoryBlock, destPath As String) As Chilkat.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 Nil on failure

UncompressString

Function UncompressString(inData As MemoryBlock, inCharset As String) As String

Decompresses Gzip-compressed data and returns the result as a string.

After decompression, the result is raw binary data (a sequence of bytes). These bytes are then interpreted as text using the specified character set (such as utf-8, iso-8859-1, etc.) to produce the final string.

Internally, Chilkat converts the byte sequence to a string by interpreting the bytes according to the specified character set. For example, if utf-8 is specified, the bytes are treated as the UTF-8 byte representation of text and decoded into the internal string format used by the programming language.

It is important that the character set matches the one originally used when the data was compressed. If the wrong character set is used, the byte-to-text conversion may produce incorrect or unreadable characters.

Returns Nil on failure

More Information and Examples

Full List of Charset Names

UncompressStringAsync ⁽¹⁾

Function UncompressStringAsync(inData As MemoryBlock, inCharset As String) As Chilkat.Task

Creates an asynchronous task to call the UncompressString 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 Nil on failure

UncompressStringENC

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

Decompresses Gzip data provided as an encoded string and returns the uncompressed result as text.

The input string is first decoded using the specified encoding, such as base64, hex, url, base32, quoted-printable, etc. The decoded Gzip data is then decompressed and converted to text using the specified character set.

Returns Nil on failure

More Information and Examples

Binary Encodings Supported by Chilkat

UnTarGz

Function UnTarGz(gzPath As String, destDir As String, bNoAbsolute As Boolean) As Boolean

Extracts a .tar.gz archive to a directory.

The Gzip decompression and TAR extraction are performed in streaming mode. No temporary files are created, and memory usage remains small and constant.

If bNoAbsolute is True, absolute paths in the TAR archive are not allowed. This helps protect against extracting files to unsafe locations, such as system directories.

Returns True for success, False for failure.

UnTarGzAsync ⁽¹⁾

Function UnTarGzAsync(gzPath As String, destDir As String, bNoAbsolute As Boolean) As Chilkat.Task

Creates an asynchronous task to call the UnTarGz 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 Nil on failure

XfdlToXml

Function XfdlToXml(xfldData As String) As String

Converts base64-encoded, Gzip-compressed XFDL data to XML text.

The input contains base64 data. The method decodes it, decompresses the Gzip data, and returns the resulting XML string.

XFDL (Extensible Forms Description Language) is an XML-based format used to define secure, interactive electronic forms—often including digital signatures and integrity protections—commonly used in government and enterprise applications.

Returns Nil on failure

Events

To implement events, your application would define and implement a class that is a subclass of Chilkat.Gzip. Your custom class would implement (i.e. override) some or all of the event methods.

For example:

class MyGzip
    Inherits Chilkat.Gzip

    Function AbortCheck() As Boolean

    Function PercentDone(pctDone As Int32) As Boolean

    Sub ProgressInfo(name As String, value As String)

    Sub TaskCompleted(task As Chilkat.Task)


End Class

AbortCheck

Function AbortCheck() As Boolean

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

Chilkat Event Callback Examples

PercentDone

Function PercentDone(pctDone As Int32) As Boolean

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

Chilkat Event Callback Examples

ProgressInfo

Sub ProgressInfo(name As String, value As String)

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

Chilkat Event Callback Examples

TaskCompleted

Sub TaskCompleted(task As Chilkat.Task)

Called from the background thread when an asynchronous task completes.

Deprecated

Decode

Function Decode(encodedStr As String, encoding As String) As MemoryBlock

This method is deprecated.

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 Nil on failure

DeflateStringENC

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

This method is deprecated.

Compresses a string using the raw deflate algorithm and returns the compressed data as an encoded string.

The input string is first converted to bytes using the specified character set. The compressed binary data is then encoded using the requested output encoding, such as hex, base64, url, or quoted-printable.

Important: This method produces raw deflate-compressed data, not Gzip-format data. Use the Compress* methods when Gzip format output is required.

Returns Nil on failure

More Information and Examples

Full List of Charset Names

Encode

Function Encode(byteData As MemoryBlock, encoding As String) As String

This method is deprecated.

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

Returns Nil on failure

GetDt

Function GetDt() As Chilkat.CkDateTime

This method is deprecated.

Applications should instead access the LastModStr property.

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

Returns Nil on failure

InflateStringENC

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

This method is deprecated.

Decompresses data previously compressed with DeflateStringENC.

The input string is first decoded using the specified input encoding, such as hex, base64, url, or quoted-printable. The resulting compressed bytes are then inflated, and the final bytes are converted to a string using the specified character set.

Returns Nil on failure

ReadFile

Function ReadFile(path As String) As MemoryBlock

This method is deprecated.

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 Nil on failure

WriteFile

Function WriteFile(path As String, binaryData As MemoryBlock) As Boolean

This method is deprecated.

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

Returns True for success, False for failure.