Gzip Lianja Reference Documentation

Gzip

Current Version: 11.4.0

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

loObject = createobject("CkGzip")

Properties

AbortCurrent
AbortCurrent As Boolean
Introduced in version 9.5.0.58

Set this property to .T. 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 .F. when the next method begins. After an abort occurs, it is also reset to .F.. Both synchronous and asynchronous operations can be aborted. For synchronous calls, another thread must set this property.

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Comment
Comment As Character

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

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CompressionLevel
CompressionLevel As Numeric
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.

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DebugLogFilePath
DebugLogFilePath As Character

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.

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Filename
Filename As Character

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.

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LastErrorHtml
LastErrorHtml As Character (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.

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LastErrorText
LastErrorText As Character (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.

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LastErrorXml
LastErrorXml As Character (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.

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LastMethodSuccess
LastMethodSuccess As Boolean

Indicates the success or failure of the most recent method call: .T. means success, .F. 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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LastModStr
LastModStr As Character

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.

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UseCurrentDate
UseCurrentDate As Boolean

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

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

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VerboseLogging
VerboseLogging As Boolean

If set to .T., then the contents of LastErrorText (or LastErrorXml, or LastErrorHtml) may contain more verbose information. The default value is .F.. 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 Character (read-only)

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

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Methods

CompressBd
CompressBd(binDat As CkBinData) 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 .T. for success, .F. for failure.

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CompressBdAsync (1)
CompressBdAsync(binDat As CkBinData) As CkTask
Introduced in version 9.5.0.67

Creates an asynchronous task to call the CompressBd method with the arguments provided.

Returns .F. on failure

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CompressFile
CompressFile(srcPath As Character, destPath As Character) As Boolean

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

Returns .T. for success, .F. for failure.

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CompressFileAsync (1)
CompressFileAsync(srcPath As Character, destPath As Character) As CkTask

Creates an asynchronous task to call the CompressFile method with the arguments provided.

Returns .F. on failure

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CompressFile2
CompressFile2(srcPath As Character, embeddedFilename As Character, destPath As Character) 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 .T. for success, .F. for failure.

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CompressFile2Async (1)
CompressFile2Async(srcPath As Character, embeddedFilename As Character, destPath As Character) As CkTask

Creates an asynchronous task to call the CompressFile2 method with the arguments provided.

Returns .F. on failure

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CompressFileBd
CompressFileBd(filePath As Character, bd As CkBinData) 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 .T. for success, .F. for failure.

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CompressFileBdAsync (1)
CompressFileBdAsync(filePath As Character, bd As CkBinData) As CkTask
Introduced in version 11.0.0

Creates an asynchronous task to call the CompressFileBd method with the arguments provided.

Returns .F. on failure

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CompressSb
CompressSb(sb As CkStringBuilder, charset As Character, bd As CkBinData) 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 .T. for success, .F. for failure.

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CompressSbAsync (1)
CompressSbAsync(sb As CkStringBuilder, charset As Character, bd As CkBinData) As CkTask
Introduced in version 11.0.0

Creates an asynchronous task to call the CompressSb method with the arguments provided.

Returns .F. on failure

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CompressStringENC
CompressStringENC(inStr As Character, charset As Character, encoding As Character) As Character

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 .F. on failure

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CompressStringToFile
CompressStringToFile(inStr As Character, destCharset As Character, destPath As Character) 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 .T. for success, .F. for failure.

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CompressStringToFileAsync (1)
CompressStringToFileAsync(inStr As Character, destCharset As Character, destPath As Character) As CkTask

Creates an asynchronous task to call the CompressStringToFile method with the arguments provided.

Returns .F. on failure

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ExamineFile
ExamineFile(filePath As Character) As Boolean

Checks whether the specified file contains Gzip-formatted data.

Returns .T. if the file is in Gzip format, or .F. otherwise.

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IsGzip
IsGzip(bd As CkBinData) As Boolean
Introduced in version 11.0.0

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

Returns .T. if the data is Gzip-formatted, or .F. otherwise.

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LoadTaskCaller
LoadTaskCaller(task As CkTask) As Boolean
Introduced in version 9.5.0.80

Loads the caller of the task's async method.

Returns .T. for success, .F. for failure.

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SetDt
SetDt(dt As 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 .T. for success, .F. for failure.

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SetExtraData
SetExtraData(encodedData As Character, encoding As Character) 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 .T. for success, .F. for failure.

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UncompressBd
UncompressBd(binDat As CkBinData) 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 .T. for success, .F. for failure.

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UncompressBdAsync (1)
UncompressBdAsync(binDat As CkBinData) As CkTask
Introduced in version 9.5.0.67

Creates an asynchronous task to call the UncompressBd method with the arguments provided.

Returns .F. on failure

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UncompressBdToFile
UncompressBdToFile(bd As CkBinData, filePath As Character) As Boolean
Introduced in version 11.0.0

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

Returns .T. for success, .F. for failure.

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UncompressBdToFileAsync (1)
UncompressBdToFileAsync(bd As CkBinData, filePath As Character) As CkTask
Introduced in version 11.0.0

Creates an asynchronous task to call the UncompressBdToFile method with the arguments provided.

Returns .F. on failure

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UncompressFile
UncompressFile(srcPath As Character, destPath As Character) 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 .T. for success, .F. for failure.

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UncompressFileAsync (1)
UncompressFileAsync(srcPath As Character, destPath As Character) As CkTask

Creates an asynchronous task to call the UncompressFile method with the arguments provided.

Returns .F. on failure

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UncompressFileToString
UncompressFileToString(srcPath As Character, charset As Character) As Character

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 .F. on failure

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UncompressFileToStringAsync (1)
UncompressFileToStringAsync(srcPath As Character, charset As Character) As CkTask

Creates an asynchronous task to call the UncompressFileToString method with the arguments provided.

Returns .F. on failure

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UncompressStringENC
UncompressStringENC(inStr As Character, charset As Character, encoding As Character) As Character

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 .F. on failure

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UnTarGz
UnTarGz(gzPath As Character, destDir As Character, 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 .T., absolute paths in the TAR archive are not allowed. This helps protect against extracting files to unsafe locations, such as system directories.

Returns .T. for success, .F. for failure.

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UnTarGzAsync (1)
UnTarGzAsync(gzPath As Character, destDir As Character, bNoAbsolute As Boolean) As CkTask

Creates an asynchronous task to call the UnTarGz method with the arguments provided.

Returns .F. on failure

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XfdlToXml
XfdlToXml(xfldData As Character) As Character

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 .F. on failure

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Deprecated

DeflateStringENC
DeflateStringENC(inString As Character, charsetName As Character, outputEncoding As Character) As Character
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 .F. on failure

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GetDt
GetDt() As 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 .F. on failure

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InflateStringENC
InflateStringENC(inString As Character, convertFromCharset As Character, inputEncoding As Character) As Character
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 .F. on failure

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