UnixCompress Dart Reference Documentation
CkUnixCompress
Current Version: 11.6.1
Chilkat.UnixCompress
Compress files, memory data, or strings into UNIX
Expand UNIX-compressed data back to files, memory, byte arrays, or text
depending on the application workflow.
Compress and uncompress directly between input and output files when
working with existing filesystem data.
Work with compressed or uncompressed byte data in memory when temporary
files are not desired.
Compress and uncompress text using an explicit character set so string
data round-trips correctly.
Use
For an extended overview, see
UnixCompress Class Overview.
Compress, uncompress, and unpack legacy UNIX
.Z files.Chilkat.UnixCompress provides UNIX compress and
uncompress functionality for legacy .Z files. It
supports file-based, memory-based, and string-based workflows, uses LZW
compression, can unpack .tar.Z archives, and includes abort and
progress-related support for longer-running operations.
Compress to .Z
.Z
format using LZW compression.
Uncompress .Z data
File workflows
Memory workflows
String workflows
Unpack tar.Z archives
UnTarZ to decompress and extract legacy
.tar.Z archives in a single workflow.
UnixCompress when the data is in classic UNIX
.Z format or when a .tar.Z archive must be
unpacked. Use Chilkat.Gzip for .gz and
.tar.gz files, Chilkat.Bz2 for
.bz2 files, and Chilkat.Compression for raw
compression algorithms and general-purpose compression workflows.
Object Creation
// pubspec.yaml:
// dependencies:
// chilkat: ^11.6.1
import 'package:chilkat/chilkat.dart';
// Once per process, before any other Chilkat call:
Chilkat.unlockBundle('Anything for 30-day trial'); // shorthand for CkGlobal().unlockBundle(..)
final unixCompress = CkUnixCompress();
// ... the native object is released when `unixCompress` is garbage collected, or now with unixCompress.dispose().Creates the underlying native Chilkat object. Use a CkUnixCompress only from the isolate that created it: Chilkat objects cannot be sent between isolates. Every call is synchronous; in a Flutter app, run long operations (network, large files) inside Isolate.run, creating the Chilkat objects inside the isolate.
Releases the native object immediately instead of waiting for garbage collection (useful for a large CkBinData or an open socket). Calling it more than once is harmless; any other use of the object afterwards throws a StateError. isDisposed tells whether it has been called.
Errors
A method that can fail throws a ChilkatException: a method whose only outcome is success or failure returns void and throws on failure; a method producing a String or an object returns it and throws where Chilkat would have returned null. The exception carries the object's LastErrorText at the time of the failure (lastErrorText), the class and method names (className, methodName) and a one-line message. Properties never throw, and methods that answer a question (has..., is..., ...) return a plain bool.
try {
unixCompress.someMethod(...);
} on ChilkatException catch (e) {
print(e); // CkUnixCompress.someMethod failed: <reason>
print(e.lastErrorText); // the full Chilkat log of the failed call
}Properties
AbortCurrent
bool get abortCurrent
set abortCurrent(bool value)
When set to true, causes the currently running method to abort. Methods that always finish quickly (i.e.have no length file operations or network communications) are not affected. If no method is running, then this property is automatically reset to false when the next method is called. When the abort occurs, this property is reset to false. Both synchronous and asynchronous method calls can be aborted. (A synchronous method call could be aborted by setting this property from a separate thread.)
DebugLogFilePath
String get debugLogFilePath
set debugLogFilePath(String value)
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.
HeartbeatMs
int get heartbeatMs
set heartbeatMs(int value)
The interval in milliseconds between each AbortCheck event callback, which enables an application to abort certain method calls before they complete. By default, HeartbeatMs is set to 0, meaning no AbortCheck event callbacks will trigger.
LastErrorHtml
String get 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
String get lastErrorText
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
String get 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
bool get lastMethodSuccess
set lastMethodSuccess(bool value)
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.
VerboseLogging
bool get verboseLogging
set verboseLogging(bool value)
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
String get version
Methods
CompressFile
Compresses a file to create a UNIX compressed file (.Z). This compression uses the LZW (Lempel-Ziv-Welch) compression algorithm.
Returns normally on success; throws a ChilkatException on failure.
CompressStringToFile
Unix compresses and creates a .Z file from string data. The charset specifies the character encoding used for the byte representation of the characters when compressed. The charset can be any one of a large number of character encodings, such as utf-8, iso-8859-1, Windows-1252, ucs-2, etc.
Returns normally on success; throws a ChilkatException on failure.
UncompressFile
Uncompresses a .Z file. (This compression uses the LZW (Lempel-Ziv-Welch) compression algorithm.)
Returns normally on success; throws a ChilkatException on failure.
UncompressFileToString
Uncompresses a .Z file that contains a text file. The contents of the text file are returned as a string. The character encoding of the text file is specified by charset. Typical charsets are iso-8859-1, utf-8, windows-1252, shift_JIS, big5, etc.
Throws a ChilkatException on failure (where the description says null is returned, the Dart method throws instead).
UnTarZ
Unpacks a .tar.Z file. The decompress and untar occur in streaming mode. There are no temporary files and the memory footprint is constant (and small) while untarring.
Returns normally on success; throws a ChilkatException on failure.
Events
All Chilkat methods are synchronous: the call returns when the work is done. During a call, CkUnixCompress raises three events so your application can show progress and offer a way out. Each event is a nullable callback property on the object; assign a function to receive it, or null to stop receiving it:
final unixCompress = CkUnixCompress();
unixCompress.onPercentDone = (pct) {
print('$pct%');
return false; // return true to abort the method in progress
};
unixCompress.onProgressInfo = (name, value) => print('$name: $value');
unixCompress.heartbeatMs = 250; // raise onAbortCheck 4 times per second during Chilkat calls
unixCompress.onAbortCheck = () => _userPressedCancel;AbortCheck fires at regular intervals controlled by the HeartbeatMs property (0, the default, disables it); PercentDone fires when an operation's completion percentage is known; ProgressInfo delivers named progress values. Returning true from onAbortCheck or onPercentDone aborts the running method, which then throws a ChilkatException.
Events fire on the thread that called the method, before that method returns. An exception thrown inside a callback aborts the running method and is rethrown from it once the native library has returned. In a Flutter app the callbacks run inside the worker isolate that owns the object; forward progress to the UI through a SendPort, and let onAbortCheck read a flag the UI sets the same way.
AbortCheck
bool Function()? onAbortCheck
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:
unixCompress.heartbeatMs = 250; // call onAbortCheck 4 times per second
var cancelRequested = false;
unixCompress.onAbortCheck = () => cancelRequested;
// ... set cancelRequested = true (e.g. from a message received on a ReceivePort) to abort the method in progressPercentDone
bool Function(int pctDone)? onPercentDone
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:
unixCompress.onPercentDone = (pct) {
// pct ranges from 1 to 100.
print('Percent done: $pct');
return false; // return true to abort the method in progress
};ProgressInfo
void Function(String name, String value)? onProgressInfo
This event callback provides tag name/value pairs that detail what occurs during a method call. To discover existing tag names, create code to handle the event, emit the pairs, and review them. Most tag names are self-explanatory.
Note: Some Chilkat methods don't fire any ProgressInfo events.
Example:
unixCompress.onProgressInfo = (name, value) => print('$name: $value');