chilkat.Gzip

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.

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

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.

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.

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.

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.

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.

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.

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.

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.

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:

Sun, 12 Apr 2026 12:45:26 GMT

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

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.

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 of the component/library, such as "10.1.0"

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

Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.

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

Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.

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 src_path parameter is the filename stored in the Gzip header and may be used by extraction tools as the output filename.

Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.

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 on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.

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 on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.

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 the string, or nil, err on failure (or when nothing is found). The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.

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 on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.

Retrieves metadata stored in a Gzip file and returns the information in a JsonObject.

The metadata is returned using the following JSON structure:

{
  "extraData": "AAECAw==",
  "filename": "example.txt",
  "comment": "This is the comment"
}

• filename – the original filename embedded in the Gzip file (if present)
• comment – an optional descriptive comment (if present)
• extraData – optional additional binary data, returned as a Base64-encoded string

Any of these fields may be omitted if they were not included when the Gzip file was created.

Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.

Retrieves metadata stored in Gzip data contained within a BinData object and returns the information in a JsonObject.

The metadata is returned using the same JSON structure:

{
  "extraData": "AAECAw==",
  "filename": "example.txt",
  "comment": "This is the comment"
}

• filename – the original filename embedded in the Gzip data (if present)
• comment – an optional descriptive comment (if present)
• extraData – optional additional binary data, returned as a Base64-encoded string

Any of these fields may be omitted if they were not included when the Gzip data was created.

Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.

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

Returns true if the data is Gzip-formatted, or false otherwise.

Returns true or false: an answer, not a success flag.

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 on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.

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 on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.

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

Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.

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

Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.

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 on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.

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 the string, or nil, err on failure (or when nothing is found). The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.

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 the string, or nil, err on failure (or when nothing is found). The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.

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 on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.

Converts encoded and compressed XFDL data to a decompressed XML string.

XFDL data is often stored in an ASCII-safe compressed form, such as asci-gzip or asc-gzip. Despite the name, this does not always mean the data is a standard .gz file. In some XFDL files, the compressed payload uses the raw deflate format rather than the full Gzip file format.

Chilkat automatically detects the actual encoding and compression format used by the XFDL data. It decodes the ASCII/Base64 representation, determines whether the compressed data is Gzip or deflate, decompresses it correctly, and returns the resulting XML string.

This allows applications to call XfdlToXml without needing to manually distinguish between XFDL variants such as Base64+Gzip and Base64+Deflate.

Returns the decoded and decompressed 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 the string, or nil, err on failure (or when nothing is found). The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.

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.

Example

local deadline = os.time() + 30                  -- give up after 30 seconds
gzip.heartbeat_ms = 250                      -- call the handler 4 times per second
gzip:set_event_handler({ abort_check = function() return os.time() > deadline end })

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.

Example

gzip:set_event_handler({
    percent_done = function(pct_done)     -- 0 to 100
        print("Percent done: " .. pct_done)
        return false                       -- return true to abort the method in progress
    end,
})

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.

Example

gzip:set_event_handler({
    progress_info = function(name, value) print(name .. ": " .. value) end,
})