Gzip C 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.
Create/Dispose
HCkGzip instance = CkGzip_Create(); // ... CkGzip_Dispose(instance);
Creates an instance of the HCkGzip object and returns a handle ("void *" pointer). The handle is passed in the 1st argument for the functions listed on this page.
Objects created by calling CkGzip_Create must be freed by calling this method. A memory leak occurs if a handle is not disposed by calling this function. Also, any handle returned by a Chilkat "C" function must also be freed by the application by calling the appropriate Dispose method, such as CkGzip_Dispose.
Callback Functions
Provides the opportunity for a method call to be aborted. If TRUE is returned, the operation in progress is aborted.
Return FALSE to allow the current method call to continue.
This callback function is called periodically based on the value of the HeartbeatMs property.
(If HeartbeatMs is 0, then no callbacks are made.) As an example, to make 5 AbortCheck callbacks per second, set the HeartbeatMs property equal to 200.
See Also:C Example using Callback Functions
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 callback is only called 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 methods 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).
This callback counts as an AbortCheck callback, and takes the place of the AbortCheck event when it fires.
The return value indicates whether the method call should be aborted, or whether it should proceed. Return TRUE to abort, and FALSE to proceed.
This is a general callback that provides name/value information about what is happening at certain points during a method call. To see the information provided in ProgressInfo callbacks, if any, write code to handle this event and log the name/value pairs. Most are self-explanatory.
Called in the background thread when an asynchronous task completes. (Note: When an async method is running, all callbacks are in the background thread.)
Properties
AbortCurrent
void CkGzip_putAbortCurrent(HCkGzip cHandle, BOOL newVal);
Set this property to TRUE
If no method is currently running, the property is automatically reset to FALSEFALSE
Comment
void CkGzip_putComment(HCkGzip cHandle, const char *newVal);
const char *CkGzip_comment(HCkGzip cHandle);
An optional comment to embed in the Gzip file when a Compress* method is called.
CompressionLevel
void CkGzip_putCompressionLevel(HCkGzip cHandle, int newVal);
Controls the compression level used when creating Gzip data. The value can range from
0 to 9.
0= no compression9= 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
void CkGzip_putDebugLogFilePath(HCkGzip cHandle, const char *newVal);
const char *CkGzip_debugLogFilePath(HCkGzip cHandle);
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.
Filename
void CkGzip_putFilename(HCkGzip cHandle, const char *newVal);
const char *CkGzip_filename(HCkGzip cHandle);
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
void CkGzip_putHeartbeatMs(HCkGzip cHandle, int newVal);
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.
LastErrorHtml
const char *CkGzip_lastErrorHtml(HCkGzip cHandle);
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.
topLastErrorText
const char *CkGzip_lastErrorText(HCkGzip cHandle);
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.
LastErrorXml
const char *CkGzip_lastErrorXml(HCkGzip cHandle);
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.
topLastMethodSuccess
void CkGzip_putLastMethodSuccess(HCkGzip cHandle, BOOL newVal);
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
void CkGzip_putLastModStr(HCkGzip cHandle, const char *newVal);
const char *CkGzip_lastModStr(HCkGzip cHandle);
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.
topUseCurrentDate
void CkGzip_putUseCurrentDate(HCkGzip cHandle, BOOL newVal);
Controls the last-modified date/time assigned to files created by Uncompress* methods.
When set to TRUE
Utf8
void CkGzip_putUtf8(HCkGzip cHandle, BOOL newVal);
When set to TRUE, all const char * arguments and return values are interpreted as UTF-8 strings. When set to FALSE, they are interpreted as ANSI strings.
In Chilkat v11.0.0 and later, the default value is TRUE. Before v11.0.0, it was FALSE.
VerboseLogging
void CkGzip_putVerboseLogging(HCkGzip cHandle, BOOL newVal);
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
const char *CkGzip_version(HCkGzip cHandle);
Methods
CompressBd
Compresses the contents of a BinData object in place, replacing the original data
with Gzip-compressed data.
Returns TRUE for success, FALSE for failure.
CompressBdAsync (1)
Creates an asynchronous task to call the CompressBd method with the arguments provided.
Returns NULL on failure
CompressFile
Compresses a file and writes the result as a Gzip file, typically with a .gz extension.
Returns TRUE for success, FALSE for failure.
CompressFileAsync (1)
Creates an asynchronous task to call the CompressFile method with the arguments provided.
Returns NULL on failure
CompressFile2
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.
CompressFile2Async (1)
Creates an asynchronous task to call the CompressFile2 method with the arguments provided.
Returns NULL on failure
CompressFileBd
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.
CompressFileBdAsync (1)
Creates an asynchronous task to call the CompressFileBd method with the arguments provided.
Returns NULL on failure
CompressSb
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.
CompressSbAsync (1)
Creates an asynchronous task to call the CompressSb method with the arguments provided.
Returns NULL on failure
CompressStringENC
const char *CkGzip_compressStringENC(HCkGzip cHandle, const char *inStr, const char *charset, const char *encoding);
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 TRUE for success, FALSE for failure.
CompressStringToFile
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.
CompressStringToFileAsync (1)
Creates an asynchronous task to call the CompressStringToFile method with the arguments provided.
Returns NULL on failure
ExamineFile
Checks whether the specified file contains Gzip-formatted data.
Returns TRUEFALSE
IsGzip
Checks whether the data contained in a BinData object is in Gzip format.
Returns TRUEFALSE
LoadTaskCaller
SetDt
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.
SetExtraData
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.
UncompressBd
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.
topUncompressBdAsync (1)
Creates an asynchronous task to call the UncompressBd method with the arguments provided.
Returns NULL on failure
UncompressBdToFile
Decompresses Gzip data stored in a BinData object and writes the result to a file.
Returns TRUE for success, FALSE for failure.
topUncompressBdToFileAsync (1)
Creates an asynchronous task to call the UncompressBdToFile method with the arguments provided.
Returns NULL on failure
UncompressFile
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.
UncompressFileAsync (1)
Creates an asynchronous task to call the UncompressFile method with the arguments provided.
Returns NULL on failure
UncompressFileToString
const char *CkGzip_uncompressFileToString(HCkGzip cHandle, const char *srcPath, const char *charset);
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 TRUE for success, FALSE for failure.
UncompressFileToStringAsync (1)
Creates an asynchronous task to call the UncompressFileToString method with the arguments provided.
Returns NULL on failure
UncompressStringENC
const char *CkGzip_uncompressStringENC(HCkGzip cHandle, const char *inStr, const char *charset, const char *encoding);
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 TRUE for success, FALSE for failure.
UnTarGz
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
Returns TRUE for success, FALSE for failure.
topUnTarGzAsync (1)
Creates an asynchronous task to call the UnTarGz method with the arguments provided.
Returns NULL on failure
XfdlToXml
const char *CkGzip_xfdlToXml(HCkGzip cHandle, const char *xfldData);
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 TRUE for success, FALSE for failure.
topDeprecated
CompressFileToMem Deprecated
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 TRUE for success, FALSE for failure.
topCompressFileToMemAsync Deprecated (1)
Creates an asynchronous task to call the CompressFileToMem method with the arguments provided.
Returns NULL on failure
CompressMemory Deprecated
Compresses a byte array and returns the result as an in-memory Gzip image.
The uncompressed input data must not exceed 4 GB.
Returns TRUE for success, FALSE for failure.
topCompressMemoryAsync Deprecated (1)
Creates an asynchronous task to call the CompressMemory method with the arguments provided.
Returns NULL on failure
CompressMemToFile Deprecated
Compresses a byte array and writes the resulting Gzip data to a file.
Returns TRUE for success, FALSE for failure.
topCompressMemToFileAsync Deprecated (1)
Creates an asynchronous task to call the CompressMemToFile method with the arguments provided.
Returns NULL on failure
CompressString Deprecated
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 TRUE for success, FALSE for failure.
CompressStringAsync Deprecated (1)
Creates an asynchronous task to call the CompressString method with the arguments provided.
Returns NULL on failure
Decode 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 TRUE for success, FALSE for failure.
topDeflateStringENC
const char *CkGzip_deflateStringENC(HCkGzip cHandle, const char *inString, const char *charsetName, const char *outputEncoding);
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 TRUE for success, FALSE for failure.
Encode Deprecated
const char *CkGzip_encode(HCkGzip cHandle, HCkByteData byteData, const char *encoding);
Encodes binary data to a printable string. The encoding mode is determined by encoding. It may be base64, hex, quoted-printable, or url.
Returns TRUE for success, FALSE for failure.
topExamineMemory Deprecated
Checks whether the provided byte array contains Gzip-formatted data.
Returns TRUEFALSE
GetDt
Applications should instead access the LastModStr property.
Gets the last-modification date/time to be embedded within the .gz.
Returns NULL on failure
InflateStringENC
const char *CkGzip_inflateStringENC(HCkGzip cHandle, const char *inString, const char *convertFromCharset, const char *inputEncoding);
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 TRUE for success, FALSE for failure.
topReadFile 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 TRUE for success, FALSE for failure.
topUncompressFileToMem Deprecated
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 TRUE for success, FALSE for failure.
topUncompressFileToMemAsync Deprecated (1)
Creates an asynchronous task to call the UncompressFileToMem method with the arguments provided.
Returns NULL on failure
UncompressMemory Deprecated
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 TRUE for success, FALSE for failure.
topUncompressMemoryAsync Deprecated (1)
Creates an asynchronous task to call the UncompressMemory method with the arguments provided.
Returns NULL on failure
UncompressMemToFile Deprecated
Decompresses an in-memory Gzip image and writes the uncompressed data to a file.
Returns TRUE for success, FALSE for failure.
topUncompressMemToFileAsync Deprecated (1)
Creates an asynchronous task to call the UncompressMemToFile method with the arguments provided.
Returns NULL on failure
UncompressString Deprecated
const char *CkGzip_uncompressString(HCkGzip cHandle, HCkByteData inData, const char *inCharset);
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 TRUE for success, FALSE for failure.
UncompressStringAsync Deprecated (1)
Creates an asynchronous task to call the UncompressString method with the arguments provided.
Returns NULL on failure
WriteFile Deprecated
A convenience method for writing a binary byte array to a file.
Returns TRUE for success, FALSE for failure.
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