UnixCompress B4X (B4A / B4J) Reference Documentation
ChilkatUnixCompress
Current Version: 11.6.0
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.
Declare / Initialize / Dispose
Sub Process_Globals
Private obj As ChilkatUnixCompress
End Sub
' Call Initialize before first use -- typically in AppStart (B4J)
' or Activity_Create (B4A):
obj.Initialize ' classes without events
obj.Initialize("evt") ' classes with events: "evt" becomes the
' prefix of event Subs such as evt_PercentDone
Creates the underlying native Chilkat object. Classes that support events take an EventName argument: it becomes the prefix of the event Subs (<EventName>_AbortCheck, <EventName>_PercentDone, <EventName>_ProgressInfo); classes without events take no arguments. The native Chilkat library loads automatically on the first Initialize — from the APK on Android, or extracted from ChilkatB4J.jar on Windows/Linux/macOS.
True if Initialize has been called and the native object exists.
Explicitly frees the underlying native object. Calling Dispose is optional — every ChilkatUnixCompress is also freed automatically when garbage-collected — but is recommended for long-lived objects holding sockets, sessions, or large buffers. A disposed object can be re-Initialized.
Properties
AbortCurrent
AbortCurrent As Boolean
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
DebugLogFilePath As String
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
HeartbeatMs As Int
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
LastErrorHtml As String
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
LastErrorText As String
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
LastErrorXml As String
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
LastMethodSuccess As Boolean
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
VerboseLogging As Boolean
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
Version As String
Methods
CompressFile
Compresses a file to create a UNIX compressed file (.Z). This compression uses the LZW (Lempel-Ziv-Welch) compression algorithm.
Returns True for success, False for failure.
topCompressStringToFile
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 True for success, False for failure.
UncompressFile
Uncompresses a .Z file. (This compression uses the LZW (Lempel-Ziv-Welch) compression algorithm.)
Returns True for success, False for failure.
topUncompressFileToString
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.
Returns Null on failure
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 True for success, False for failure.
topEvents
All Chilkat methods are synchronous: the call returns when the work is done. During a call, ChilkatUnixCompress raises three events so your application can show progress and offer a way out. The event-name prefix is the string passed to Initialize:
uc.Initialize("evt") ' event Subs are named evt_AbortCheck, evt_PercentDone, evt_ProgressInfo
uc.HeartbeatMs = 250 ' raise evt_AbortCheck 4 times per second during Chilkat callsAbortCheck 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 an AbortCheck or PercentDone Sub aborts the running method. Implement only the Subs you need — events are skipped entirely when no matching Sub exists.
If a Chilkat call runs on a separate thread (e.g. via the Threading library), its events are automatically queued to the main thread. Events raised that way cannot abort by return value; set the object's AbortCurrent property to True instead.
AbortCheck
' Return True to abort the Chilkat method in progress.
Sub evt_AbortCheck As Boolean
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 (object initialized with uc.Initialize("evt")):
uc.HeartbeatMs = 250 ' fire evt_AbortCheck 4 times per second
Sub evt_AbortCheck As Boolean
' Called every HeartbeatMs milliseconds while a Chilkat method is running.
Return False ' Return True to abort the method in progress
End SubPercentDone
' Return True to abort the Chilkat method in progress.
Sub evt_PercentDone (PctDone As Int) As Boolean
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 (object initialized with uc.Initialize("evt")):
Sub evt_PercentDone (PctDone As Int) As Boolean
' PctDone ranges from 1 to 100.
Log("Percent done: " & PctDone)
Return False ' Return True to abort the method in progress
End SubProgressInfo
Sub evt_ProgressInfo (Name As String, Value As String)
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 (object initialized with uc.Initialize("evt")):
Sub evt_ProgressInfo (Name As String, Value As String)
Log(Name & ": " & Value)
End Sub