UnixCompress B4X (B4A / B4J) Reference Documentation

ChilkatUnixCompress

Current Version: 11.6.0

Chilkat.UnixCompress

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

Compress files, memory data, or strings into UNIX .Z format using LZW compression.

Uncompress .Z data

Expand UNIX-compressed data back to files, memory, byte arrays, or text depending on the application workflow.

File workflows

Compress and uncompress directly between input and output files when working with existing filesystem data.

Memory workflows

Work with compressed or uncompressed byte data in memory when temporary files are not desired.

String workflows

Compress and uncompress text using an explicit character set so string data round-trips correctly.

Unpack tar.Z archives

Use UnTarZ to decompress and extract legacy .tar.Z archives in a single workflow.

Common pattern: Use 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
Initialize  /  Initialize (EventName As String)

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.

IsInitialized As Boolean

True if Initialize has been called and the native object exists.

Dispose

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
' read/write
AbortCurrent As Boolean
Introduced in version 9.5.0.58

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.)

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DebugLogFilePath
' read/write
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.

More Information and Examples
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HeartbeatMs
' read/write
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.

More Information and Examples
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LastErrorHtml
' read-only
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.

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LastErrorText
' read-only
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.

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LastErrorXml
' read-only
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.

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LastMethodSuccess
' read/write
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.

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VerboseLogging
' read/write
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.

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Version
' read-only
Version As String

Version of the component/library, such as "10.1.0"

More Information and Examples
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Methods

CompressFile
CompressFile (inFilename As String, destPath As String) As Boolean

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.

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CompressStringToFile
CompressStringToFile (inStr As String, charset As String, destPath As String) As Boolean

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.

More Information and Examples
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UncompressFile
UncompressFile (inFilename As String, destPath As String) As Boolean

Uncompresses a .Z file. (This compression uses the LZW (Lempel-Ziv-Welch) compression algorithm.)

Returns True for success, False for failure.

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UncompressFileToString
UncompressFileToString (zFilename As String, charset As String) As String

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

More Information and Examples
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UnTarZ
UnTarZ (zFilename As String, destDir As String, bNoAbsolute As Boolean) As Boolean

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.

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Events

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 calls

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 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
' evt = the EventName passed to Initialize
' 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.

More Information and Examples

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 Sub
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PercentDone
' evt = the EventName passed to Initialize
' 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.

More Information and Examples

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 Sub
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ProgressInfo
' evt = the EventName passed to Initialize
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.

More Information and Examples

Example (object initialized with uc.Initialize("evt")):

Sub evt_ProgressInfo (Name As String, Value As String)
    Log(Name & ": " & Value)
End Sub
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