---
product: Chilkat
product_version: 11.7.0
language: pascal
language_label: Lazarus Pascal
class: Bz2
license: bundle
deprecated: false
reference_html: https://www.chilkatsoft.com/refdoc/pascal_Bz2Ref.html
---
# Chilkat Bz2 — Lazarus Pascal — v11.7.0

> Chilkat 11.7.0 · language=pascal · class=Bz2
> Other versions: replace `11.7.0` in this URL. Other languages: `https://www.chilkatsoft.com/ai-docs/v/11.7.0/<lang>/classes/Bz2.md`.
> Language-wide rules (install, unlock, error model, strings/bytes): `https://www.chilkatsoft.com/ai-docs/v/11.7.0/pascal/guide.md`.

## Purpose

`Chilkat.Bz2` provides BZip2 compression and decompression for files, memory buffers, and BinData. It can create standard .bz2 file images, decompress .bz2 content back to its original bytes, and support abortable long-running operations.

For an extended overview, see [Bz2 Class Overview](https://www.chilkatsoft.com/bz2_class_overview.asp)

## Object creation, unlocking and error handling

**Create / Free**

```pascal
uses
  Chilkat.Bz2;

var
  obj: TBz2;
begin
  obj := TBz2.Create;
  try
    if not obj.IsValid then
      raise Exception.Create('Failed to create a TBz2 instance.');

    // ... use obj ...

  finally
    obj.Free;
  end;
end;
```

`constructor Create;`

Allocates the underlying CkBz2 object and returns a new TBz2 instance. Simply adding **Chilkat.Bz2** to the unit's `uses` clause is enough to locate and bind to the Chilkat shared library (DLL / .so / .dylib) at runtime — no separate load step is required. Check `obj.IsValid` after calling `Create`; it is `False` if the underlying library could not be found/loaded or the object could not be allocated (for example, when unlicensed).

`destructor Destroy; override;`

Every TBz2 created by calling `Create` should eventually be released by calling `.Free` (inherited from `TObject`). The destructor automatically disposes the underlying CkBz2 handle. A native (unmanaged) memory leak occurs if the object is never freed.

Call `Global.UnlockBundle` once at the start of the program, before using this or any other Chilkat class. Any string unlocks a fully functional 30-day trial; a purchased unlock code is used in production. See `guide.md` for the exact code in Lazarus Pascal.

## Members common to every Chilkat class

Documented once per language in `common-members.md`; listed here so this page is self-contained.

| Property | Signature | Access | Meaning |
|---|---|---|---|
| `DebugLogFilePath` | `property DebugLogFilePath: string read GetDebugLogFilePath write SetDebugLogFilePath;` | read/write | If set to a file path, this property logs the LastErrorText of each Chilkat method or property call to the specified file. |
| `LastErrorHtml` | `property LastErrorHtml: string read GetLastErrorHtml;` | read-only | Provides HTML-formatted information about the last called method or property. |
| `LastErrorText` | `property LastErrorText: string read GetLastErrorText;` | read-only | Provides plain text information about the last called method or property. |
| `LastErrorXml` | `property LastErrorXml: string read GetLastErrorXml;` | read-only | Provides XML-formatted information about the last called method or property. |
| `LastMethodSuccess` | `property LastMethodSuccess: Boolean read GetLastMethodSuccess write SetLastMethodSuccess;` | read/write | Indicates the success or failure of the most recent method call: `True` means success, `False` means failure. |
| `VerboseLogging` | `property VerboseLogging: Boolean read GetVerboseLogging write SetVerboseLogging;` | read/write | If set to `True`, then the contents of LastErrorText (or LastErrorXml, or LastErrorHtml) may contain more verbose information. |
| `Version` | `property Version: string read GetVersion;` | read-only | Version of the component/library, such as "10.1.0" |

## Member index

| Member | Kind | Signature |
|---|---|---|
| `AbortCurrent` | property, read/write | `property AbortCurrent: Boolean read GetAbortCurrent write SetAbortCurrent;` |
| `HeartbeatMs` | property, read/write | `property HeartbeatMs: Integer read GetHeartbeatMs write SetHeartbeatMs;` |
| `CompressBd` | method | `// bd is a TBinData object. function CompressBd(bd: TChilkatBase): Boolean;` |
| `CompressFile` | method | `function CompressFile(const inFilename: string;     const toPath: string): Boolean;` |
| `LoadTaskCaller` | method | `// task is a TTask object. function LoadTaskCaller(task: TChilkatBase): Boolean;` |
| `UncompressBd` | method | `// bd is a TBinData object. function UncompressBd(bd: TChilkatBase): Boolean;` |
| `UncompressFile` | method | `function UncompressFile(const inFilename: string;     const toPath: string): Boolean;` |

## Properties

### Bz2.AbortCurrent

`Chilkat 11.7.0 · pascal · Bz2 · AbortCurrent · property · read/write · since 9.5.0.58`

```pascal
property AbortCurrent: Boolean read GetAbortCurrent write SetAbortCurrent;
```

Set this property to `True` to request cancellation of the compression or decompression operation currently executing on this object. Long-running operations check the request periodically; an operation that finishes quickly may complete before the request is observed.

A synchronous call can be cancelled by setting this property from another thread. After cancellation is processed, Chilkat resets the property to `False`. If no operation is running, a previously set value is cleared when the next method begins.

**Cancellation is cooperative:** Setting this property requests an abort; it does not guarantee immediate termination. Check the method's return value and `LastErrorText` to determine the final outcome.

### Bz2.HeartbeatMs

`Chilkat 11.7.0 · pascal · Bz2 · HeartbeatMs · property · read/write`

```pascal
property HeartbeatMs: Integer read GetHeartbeatMs write SetHeartbeatMs;
```

**Full documentation for this property (same in every language):** [Event Callback Examples](https://www.chilkatsoft.com/ai-docs/v/11.7.0/articles/event_callback_examples.md)

Specifies the interval, in milliseconds, between `AbortCheck` event callbacks during supported long-running compression and decompression operations. The default is `0`, which disables `AbortCheck` callbacks.

Set a positive value, such as `200`, when the application needs periodic opportunities to request cancellation. The interval is approximate; callbacks occur only while an operation is at a point where progress events can be delivered.

**Cancellation workflow:** In an `AbortCheck` handler, set the callback's abort value to request termination. A synchronous method may also be cancelled from another thread by setting `AbortCurrent` to `True`.

## Methods

### Bz2.CompressBd

`Chilkat 11.7.0 · pascal · Bz2 · CompressBd · method · since 11.0.0`

```pascal
// bd is a TBinData object.

function  CompressBd(bd: TChilkatBase): Boolean;
```

Compresses the current contents of `bd` in place. On success, the `BinData` no longer contains the original bytes; it contains the complete standard BZip2 stream that may be saved with a `.bz2` extension.

**In-place transformation:** Preserve a copy of the original data if it is still needed after this call. A BZip2 stream contains a stream header, one or more compressed blocks with integrity checks, and an end-of-stream marker. It does not contain archive filenames or directory entries.

Returns True for success, False for failure.

### Bz2.CompressFile

`Chilkat 11.7.0 · pascal · Bz2 · CompressFile · method`

```pascal
function  CompressFile(const inFilename: string;
    const toPath: string): Boolean;
```

Reads the file at `inFilename` and writes its compressed bytes as a standard BZip2 stream to the file at `toPath`. The output is conventionally given a `.bz2` extension.

Both arguments must identify files, not directories. They may be absolute or relative paths, for example `data/report.txt` and `data/report.txt.bz2`.

**BZip2 is a compressor, not an archive format:** A `.bz2` file represents one compressed byte stream. It does not store the original filename, directory path, timestamps, permissions, or multiple archive entries. Formats such as `.tar.bz2` first combine files in a TAR archive and then compress that TAR stream with BZip2.

Returns True for success, False for failure.

### Bz2.LoadTaskCaller

`Chilkat 11.7.0 · pascal · Bz2 · LoadTaskCaller · method · since 9.5.0.80`

```pascal
// task is a TTask object.

function  LoadTaskCaller(task: TChilkatBase): Boolean;
```

Loads this `Bz2` object with the caller state associated with the asynchronous operation represented by `task`.

**Advanced async infrastructure:** This method is used to recover the original caller object associated with a completed task. It is not normally needed by application code. Pass a `Task` created by a compatible `Bz2` asynchronous method; an unrelated task cannot be loaded.

Returns True for success, False for failure.

### Bz2.UncompressBd

`Chilkat 11.7.0 · pascal · Bz2 · UncompressBd · method · since 11.0.0`

```pascal
// bd is a TBinData object.

function  UncompressBd(bd: TChilkatBase): Boolean;
```

Decompresses the BZip2 stream currently contained in `bd` in place. On success, the `BinData` is replaced with the original uncompressed bytes.

**Input requirement:** `bd` must contain a complete, valid BZip2 stream, such as the bytes of a `.bz2` file or the output of `CompressBd`. This method operates on binary data and does not perform character-set conversion.

Returns True for success, False for failure.

### Bz2.UncompressFile

`Chilkat 11.7.0 · pascal · Bz2 · UncompressFile · method`

```pascal
function  UncompressFile(const inFilename: string;
    const toPath: string): Boolean;
```

Reads the BZip2 stream from the file at `inFilename`, decompresses it, and writes the original uncompressed bytes to the file at `toPath`.

Both arguments must identify files, not directories. Chilkat does not derive the destination name from the `.bz2` filename because the BZip2 stream does not contain the original filename.

**Terminology:** This method decompresses BZip2 data; it does not “unzip” a ZIP archive. A `.bz2` file normally contains a single compressed byte stream rather than a collection of named files.

Returns True for success, False for failure.

## Events and callbacks

Chilkat for Pascal supports three synchronous event callbacks: `OnAbortCheck`, `OnPercentDone`, and `OnProgressInfo`. Each is a property of the class; assign a method of one of your own objects (an *of object* handler) to receive the callbacks, or assign `nil` to unhook. The handler types are declared in the `Chilkat.Base` unit:

```pascal
TChilkatAbortCheckEvent   = function(Sender: TChilkatBase): Boolean of object;
TChilkatPercentDoneEvent  = function(Sender: TChilkatBase; PctDone: Integer): Boolean of object;
TChilkatProgressInfoEvent = procedure(Sender: TChilkatBase; const Name, Value: string) of object;
```

All Chilkat methods are synchronous, so callbacks are invoked on the thread that called the method -- if the method was called from the main thread, it is safe to access UI elements from the handler. The `HeartbeatMs` property controls the frequency of `OnAbortCheck` callbacks (the default of 0 means no AbortCheck events fire). Returning `True` from an `OnAbortCheck` or `OnPercentDone` handler aborts the running method.

### Bz2.AbortCheck (event)

`Chilkat 11.7.0 · pascal · Bz2 · AbortCheck · event`

```pascal
// TChilkatAbortCheckEvent = function(Sender: TChilkatBase): Boolean of object;

property OnAbortCheck: TChilkatAbortCheckEvent;
```

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.

**Event callback implementation:**

```pascal
// A handler is a method of one of your own classes, e.g. a form:
function TMyObject.Bz2AbortCheck(Sender: TChilkatBase): Boolean;
begin
  // Called every HeartbeatMs milliseconds while a method is running.
  // Return True to abort the method; return False to continue.
  Result := False;
end;
```

**To add an event handler:**

```pascal
bz := TBz2.Create;
bz.HeartbeatMs := 250;   // fire OnAbortCheck 4 times per second
bz.OnAbortCheck := MyObject.Bz2AbortCheck;
```

### Bz2.PercentDone (event)

`Chilkat 11.7.0 · pascal · Bz2 · PercentDone · event`

```pascal
// TChilkatPercentDoneEvent = function(Sender: TChilkatBase; PctDone: Integer): Boolean of object;

property OnPercentDone: TChilkatPercentDoneEvent;
```

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.

**Event callback implementation:**

```pascal
// A handler is a method of one of your own classes, e.g. a form:
function TMyObject.Bz2PercentDone(Sender: TChilkatBase; PctDone: Integer): Boolean;
begin
  // PctDone ranges from 1 to 100.
  WriteLn('Percent done: ', PctDone);
  // Return True to abort the method; return False to continue.
  Result := False;
end;
```

**To add an event handler:**

```pascal
bz := TBz2.Create;
bz.OnPercentDone := MyObject.Bz2PercentDone;
```

### Bz2.ProgressInfo (event)

`Chilkat 11.7.0 · pascal · Bz2 · ProgressInfo · event`

```pascal
// TChilkatProgressInfoEvent = procedure(Sender: TChilkatBase; const Name, Value: string) of object;

property OnProgressInfo: TChilkatProgressInfoEvent;
```

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.

**Event callback implementation:**

```pascal
// A handler is a method of one of your own classes, e.g. a form:
procedure TMyObject.Bz2ProgressInfo(Sender: TChilkatBase; const Name, Value: string);
begin
  WriteLn(Name, ': ', Value);
end;
```

**To add an event handler:**

```pascal
bz := TBz2.Create;
bz.OnProgressInfo := MyObject.Bz2ProgressInfo;
```

## Related classes

[`BinData`](https://www.chilkatsoft.com/ai-docs/v/11.7.0/pascal/classes/BinData.md)