Gzip Objective-C Reference Documentation
CkoGzip
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
CkoGzip *obj = [[CkoGzip alloc] init];
Properties
AbortCurrent
Set this property to YES
If no method is currently running, the property is automatically reset to NONO
Comment
An optional comment to embed in the Gzip file when a Compress* method is called.
CompressionLevel
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
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
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
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
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
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
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
Indicates the success or failure of the most recent method call: YES means success, NO 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
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
Controls the last-modified date/time assigned to files created by Uncompress* methods.
When set to YES
VerboseLogging
If set to YES, then the contents of LastErrorText (or LastErrorXml, or LastErrorHtml) may contain more verbose information. The default value is NO. Verbose logging should only be used for debugging. The potentially large quantity of logged information may adversely affect peformance.
Version
Methods
CompressBd
Compresses the contents of a BinData object in place, replacing the original data
with Gzip-compressed data.
Returns YES for success, NO for failure.
CompressBdAsync (1)
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
destPath:(NSString *)destPath;
Compresses a file and writes the result as a Gzip file, typically with a .gz extension.
Returns YES for success, NO for failure.
CompressFileAsync (1)
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
embeddedFilename:(NSString *)embeddedFilename
destPath:(NSString *)destPath;
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 YES for success, NO for failure.
CompressFile2Async (1)
embeddedFilename:(NSString *)embeddedFilename
destPath:(NSString *)destPath;
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
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 YES for success, NO for failure.
CompressFileBdAsync (1)
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
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)
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
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)
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
destPath:(NSString *)destPath;
Compresses a byte array and writes the resulting Gzip data to a file.
Returns YES for success, NO for failure.
topCompressMemToFileAsync (1)
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
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 YES for success, NO for failure.
CompressSbAsync (1)
charset:(NSString *)charset
bd:(CkoBinData *)bd;
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
destCharset:(NSString *)destCharset;
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
CompressStringAsync (1)
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
charset:(NSString *)charset
encoding:(NSString *)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 nil on failure
CompressStringToFile
destCharset:(NSString *)destCharset
destPath:(NSString *)destPath;
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 YES for success, NO for failure.
CompressStringToFileAsync (1)
destCharset:(NSString *)destCharset
destPath:(NSString *)destPath;
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
Checks whether the specified file contains Gzip-formatted data.
Returns YESNO
ExamineMemory
Checks whether the provided byte array contains Gzip-formatted data.
Returns YESNO
IsGzip
Checks whether the data contained in a BinData object is in Gzip format.
Returns YESNO
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 YES for success, NO for failure.
SetExtraData
encoding:(NSString *)encoding;
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 YES for success, NO for failure.
UncompressBd
Decompresses Gzip data contained in a BinData object in place, replacing the
compressed data with the uncompressed data.
Returns YES for success, NO for failure.
topUncompressBdAsync (1)
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
Decompresses Gzip data stored in a BinData object and writes the result to a file.
Returns YES for success, NO for failure.
topUncompressBdToFileAsync (1)
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
destPath:(NSString *)destPath;
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 YES for success, NO for failure.
UncompressFileAsync (1)
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
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)
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
inCharset:(NSString *)inCharset;
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
UncompressFileToStringAsync (1)
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
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)
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
destPath:(NSString *)destPath;
Decompresses an in-memory Gzip image and writes the uncompressed data to a file.
Returns YES for success, NO for failure.
topUncompressMemToFileAsync (1)
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
inCharset:(NSString *)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 nil on failure
UncompressStringAsync (1)
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
charset:(NSString *)charset
encoding:(NSString *)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 nil on failure
UnTarGz
destDir:(NSString *)destDir
bNoAbsolute:(BOOL)bNoAbsolute;
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 YES
Returns YES for success, NO for failure.
topUnTarGzAsync (1)
destDir:(NSString *)destDir
bNoAbsolute:(BOOL)bNoAbsolute;
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
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 an event callback, your application would define and implement a class that inherits from CkoBaseProgress. Your application can implement methods to override some or all of the default/empty method implementations of the CkoBaseProgress base class.
For example:
CkoGzip *gzip = [[CkoGzip alloc] init]; MyGzipProgress *callbackObj = [[MyGzipProgress alloc] init]; [gzip setEventCallbackObject:callbackObj];
MyGzipProgress interface example:
#import "CkoGzipProgress.h"
@interface MyGzipProgress : CkoBaseProgress {
}
- (id)init;
- (void)dealloc;
- (void)dispose;
- (void)AbortCheck:(BOOL *)abort;
- (void)PercentDone:(NSNumber *)pctDone
abort:(BOOL *)abort;
- (void)ProgressInfo:(NSString *)name
value:(NSString *)value;
- (void)TaskCompleted:(CkoTask *)task;
@endAbortCheck
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.
PercentDone
abort:(BOOL *)abort;
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 YES. This will cause the method to terminate and return a failure status or corresponding failure value.
ProgressInfo
value:(NSString *)value;
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.
TaskCompleted
Called from the background thread when an asynchronous task completes.
Deprecated
Decode
encoding:(NSString *)encoding;
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
charset:(NSString *)charset
encoding:(NSString *)encoding;
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
Encode
encoding:(NSString *)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 nil on failure
GetDt
Applications should instead access the LastModStr property.
Gets the last-modification date/time to be embedded within the .gz.
Returns nil on failure
InflateStringENC
charset:(NSString *)charset
encoding:(NSString *)encoding;
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
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
binaryData:(NSData *)binaryData;
A convenience method for writing a binary byte array to a file.
Returns YES for success, NO for failure.
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