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

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

## Purpose

**Calculate ZIP-compatible CRC32 values for files, bytes, strings, and streamed data.**

`Chilkat.ZipCrc` calculates the 32-bit CRC value used in ZIP file headers. It can compute CRC32 values for in-memory byte arrays, `BinData`, `StringBuilder` content, strings using a specified character encoding, and entire files. It also supports streaming CRC calculation, allowing applications to process large or incremental data in chunks without holding the full input in memory.

**CRC32 for byte data**

Use `CalculateCrc` to calculate a ZIP-style CRC32 value for an in-memory byte array.

**BinData support**

Use `CrcBd` when the input bytes are already stored in a `Chilkat.BinData` object.

**String CRCs**

Use `CrcString` or `CrcSb` to calculate CRC32 for text using a specific charset such as `utf-8`, `utf-16`, or `windows-1252`.

**File CRCs**

Use `FileCrc` to calculate the CRC32 of a file while streaming the file contents to keep memory usage small and constant.

**Streaming calculation**

Call `BeginStream`, add chunks with `MoreData`, and finish with `EndStream` when data arrives incrementally.

**Hex formatting**

Use `ToHex` to convert a 32-bit CRC integer into a readable hexadecimal string.

**Common pattern:** Use `FileCrc` for files, `CalculateCrc` or `CrcBd` for binary data already in memory, and `CrcString` or `CrcSb` for text where the byte representation depends on a charset. For large or chunked input, initialize the CRC with `BeginStream`, feed each block with `MoreData`, and call `EndStream` to obtain the final CRC32 value.

**ZIP compatibility note:** The CRC returned by this class is the same 32-bit CRC value that would appear in a ZIP file header for the same byte content. When calculating CRCs for strings, the selected charset matters because the CRC is computed over bytes, not abstract characters.

## Object creation, unlocking and error handling

**Create / Free**

```pascal
uses
  Chilkat.ZipCrc;

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

    // ... use obj ...

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

`constructor Create;`

Allocates the underlying CkZipCrc object and returns a new TZipCrc instance. Simply adding **Chilkat.ZipCrc** 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 TZipCrc created by calling `Create` should eventually be released by calling `.Free` (inherited from `TObject`). The destructor automatically disposes the underlying CkZipCrc 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 |
|---|---|---|
| `BeginStream` | method | `procedure BeginStream;` |
| `CrcBd` | method | `// bd is a TBinData object. function CrcBd(bd: TChilkatBase): LongWord;` |
| `CrcSb` | method | `// sb is a TStringBuilder object. function CrcSb(sb: TChilkatBase;     const charset: string): LongWord;` |
| `CrcString` | method | `function CrcString(const str: string;     const charset: string): LongWord;` |
| `EndStream` | method | `function EndStream: LongWord;` |
| `FileCrc` | method | `function FileCrc(const path: string): LongWord;` |
| `LoadTaskCaller` | method | `// task is a TTask object. function LoadTaskCaller(task: TChilkatBase): Boolean;` |
| `ToHex` | method | `function ToHex(crc: LongWord): string;` |

## Methods

### ZipCrc.BeginStream

`Chilkat 11.7.0 · pascal · ZipCrc · BeginStream · method`

```pascal
procedure BeginStream;
```

Provides a way to calculate a CRC by streaming the data a chunk at a time. An application would start by calling BeginStream. Then it would add data by calling MoreData for each additional chunk. After the last chunk has been processed, the EndStream method is called to return the CRC.

### ZipCrc.CrcBd

`Chilkat 11.7.0 · pascal · ZipCrc · CrcBd · method · since 9.5.0.75`

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

function  CrcBd(bd: TChilkatBase): LongWord;
```

Calculates a CRC32 for the bytes contained in `bd`.

### ZipCrc.CrcSb

`Chilkat 11.7.0 · pascal · ZipCrc · CrcSb · method · since 9.5.0.75`

```pascal
// sb is a TStringBuilder object.

function  CrcSb(sb: TChilkatBase;
    const charset: string): LongWord;
```

Calculates a CRC32 for the string contained in `sb`. The `charset` is the byte representation to be used for the `sb` when calculating the CRC32. It can be utf-8, utf-16, windows-1252, iso-8859-1, or any of the character encodings (charsets) listed at the link below.

### ZipCrc.CrcString

`Chilkat 11.7.0 · pascal · ZipCrc · CrcString · method · since 9.5.0.75`

```pascal
function  CrcString(const str: string;
    const charset: string): LongWord;
```

Calculates a CRC32 for a string. The `charset` is the byte representation to be used for the `str` when calculating the CRC32. It can be utf-8, utf-16, windows-1252, iso-8859-1, or any of the character encodings (charsets) listed at the link below.

### ZipCrc.EndStream

`Chilkat 11.7.0 · pascal · ZipCrc · EndStream · method`

```pascal
function  EndStream: LongWord;
```

Finalizes and returns the Zip CRC value calculated by calling BeginStream followed by multiple calls to MoreData.

### ZipCrc.FileCrc

`Chilkat 11.7.0 · pascal · ZipCrc · FileCrc · method`

```pascal
function  FileCrc(const path: string): LongWord;
```

Calculates the CRC32 of a file. The data contained in the file is streamed for the calculation to keep the memory footprint small and constant. Returns the CRC32 of the file.

### ZipCrc.LoadTaskCaller

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

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

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

Loads the caller of the task's async method.

Returns True for success, False for failure.

### ZipCrc.ToHex

`Chilkat 11.7.0 · pascal · ZipCrc · ToHex · method`

```pascal
function  ToHex(crc: LongWord): string;
```

Converts a 32-bit integer to a hex string.

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.

### ZipCrc.AbortCheck (event)

`Chilkat 11.7.0 · pascal · ZipCrc · 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.ZipCrcAbortCheck(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
zipcrc := TZipCrc.Create;
zipcrc.HeartbeatMs := 250;   // fire OnAbortCheck 4 times per second
zipcrc.OnAbortCheck := MyObject.ZipCrcAbortCheck;
```

### ZipCrc.PercentDone (event)

`Chilkat 11.7.0 · pascal · ZipCrc · 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.ZipCrcPercentDone(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
zipcrc := TZipCrc.Create;
zipcrc.OnPercentDone := MyObject.ZipCrcPercentDone;
```

### ZipCrc.ProgressInfo (event)

`Chilkat 11.7.0 · pascal · ZipCrc · 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.ZipCrcProgressInfo(Sender: TChilkatBase; const Name, Value: string);
begin
  WriteLn(Name, ': ', Value);
end;
```

**To add an event handler:**

```pascal
zipcrc := TZipCrc.Create;
zipcrc.OnProgressInfo := MyObject.ZipCrcProgressInfo;
```

## Related classes

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