---
product: Chilkat
product_version: 11.7.0
language: activex
language_label: ActiveX
class: ZipCrc
license: bundle
deprecated: false
reference_html: https://www.chilkatsoft.com/refdoc/xChilkatZipCrcRef.html
---
# Chilkat ZipCrc — ActiveX — v11.7.0

> Chilkat 11.7.0 · language=activex · 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/activex/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

**Object Creation**

```clike
Note:
For a specific major version, use "Chilkat.ZipCrc.<major_version>", such as "Chilkat.ZipCrc.10" for Chilkat v10.*.*
See Chilkat ActiveX Object Creation

(ASP)
set obj = Server.CreateObject("Chilkat.ZipCrc")

(AutoIt)
$obj = ObjCreate("Chilkat.ZipCrc")

(Visual Basic 6.0)
Dim obj As New ChilkatZipCrc

(VBScript)
set obj = CreateObject("Chilkat.ZipCrc")

(VBA, such as Excel)
Dim obj As New ChilkatZipCrc
See How to Use ActiveX in Excel

(Delphi)
obj := TChilkatZipCrc.Create(Self);

(FoxPro)
loObject = CreateObject('Chilkat.ZipCrc')

(Xbase++)
oObject := CreateObject("Chilkat.ZipCrc")

(PowerBuilder)
lole_object = create oleobject
li_rc = lole_object.ConnectToNewObject("Chilkat.ZipCrc")

(SQL Server)
EXEC @hr = sp_OACreate 'Chilkat.ZipCrc', @obj OUT

(Javascript)
var obj = new ActiveXObject("Chilkat.ZipCrc");
```

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 ActiveX.

How failure is reported depends on the method's return type and is stated in the note under each method below. In every case the diagnostic text is in the `LastErrorText` property of the object whose method was called.

## 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` | `DebugLogFilePath As String` | read/write | If set to a file path, this property logs the LastErrorText of each Chilkat method or property call to the specified file. |
| `LastBinaryResult` | `LastBinaryResult As Variant (read-only)` | read-only | This property is mainly used in SQL Server stored procedures to retrieve binary data from the last method call that returned binary data. |
| `LastErrorHtml` | `LastErrorHtml As String (read-only)` | read-only | Provides HTML-formatted information about the last called method or property. |
| `LastErrorText` | `LastErrorText As String (read-only)` | read-only | Provides plain text information about the last called method or property. |
| `LastErrorXml` | `LastErrorXml As String (read-only)` | read-only | Provides XML-formatted information about the last called method or property. |
| `LastMethodSuccess` | `LastMethodSuccess As Long` | read/write | Indicates the success or failure of the most recent method call: `1` means success, `0` means failure. |
| `LastStringResult` | `LastStringResult As String (read-only)` | read-only | In SQL Server stored procedures, this property holds the string return value of the most recent method call that returns a string. |
| `LastStringResultLen` | `LastStringResultLen As Long (read-only)` | read-only | The length, in characters, of the string contained in the LastStringResult property. |
| `VerboseLogging` | `VerboseLogging As Long` | read/write | If set to `1`, then the contents of LastErrorText (or LastErrorXml, or LastErrorHtml) may contain more verbose information. |
| `Version` | `Version As String (read-only)` | read-only | Version of the component/library, such as "10.1.0" |

## Member index

| Member | Kind | Signature |
|---|---|---|
| `BeginStream` | method | `BeginStream()` |
| `CalculateCrc` | method | `CalculateCrc(data As Variant) As Long` |
| `CrcBd` | method | `CrcBd(bd As ChilkatBinData) As Long` |
| `CrcSb` | method | `CrcSb(sb As ChilkatStringBuilder, charset As String) As Long` |
| `CrcString` | method | `CrcString(str As String, charset As String) As Long` |
| `EndStream` | method | `EndStream() As Long` |
| `FileCrc` | method | `FileCrc(path As String) As Long` |
| `LoadTaskCaller` | method | `LoadTaskCaller(task As ChilkatTask) As Long` |
| `MoreData` | method | `MoreData(data As Variant)` |
| `ToHex` | method | `ToHex(ByVal crc As Long) As String` |

## Methods

### ZipCrc.BeginStream

`Chilkat 11.7.0 · activex · ZipCrc · BeginStream · method`

```
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.CalculateCrc

`Chilkat 11.7.0 · activex · ZipCrc · CalculateCrc · method`

```
CalculateCrc(data As Variant) As Long
```

Calculates a 32-bit CRC for in-memory byte data. This is the 32-bit CRC that would be found in a Zip file header if a file containing the `data` was added to a zip archive. Returns the CRC32 of the data.

### ZipCrc.CrcBd

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

```
CrcBd(bd As ChilkatBinData) As Long
```

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

### ZipCrc.CrcSb

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

```
CrcSb(sb As ChilkatStringBuilder, charset As String) As Long
```

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 · activex · ZipCrc · CrcString · method · since 9.5.0.75`

```
CrcString(str As String, charset As String) As Long
```

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 · activex · ZipCrc · EndStream · method`

```
EndStream() As Long
```

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

### ZipCrc.FileCrc

`Chilkat 11.7.0 · activex · ZipCrc · FileCrc · method`

```
FileCrc(path As String) As Long
```

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.

Async variant: `FileCrcAsync` — same arguments, returns a `Task` (see Async variants below).

### ZipCrc.LoadTaskCaller

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

```
LoadTaskCaller(task As ChilkatTask) As Long
```

Loads the caller of the task's async method.

Returns 1 for success, 0 for failure.

### ZipCrc.MoreData

`Chilkat 11.7.0 · activex · ZipCrc · MoreData · method`

```
MoreData(data As Variant)
```

Adds additional data to the CRC currently being calculated. (See BeginStream for more information.)

### ZipCrc.ToHex

`Chilkat 11.7.0 · activex · ZipCrc · ToHex · method`

```
ToHex(ByVal crc As Long) As String
```

Converts a 32-bit integer to a hex string.

Returns `Nothing` on failure

## Events and callbacks

### ZipCrc.AbortCheck (event)

`Chilkat 11.7.0 · activex · ZipCrc · AbortCheck · event`

```
AbortCheck(abort As Long)
```

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.

**VB6 Event callback implementation:**

**Important:** Event callbacks from ***asynchronous method calls*** are generally not possible from the ActiveX. See [VB6 Event Callbacks](https://www.chilkatsoft.com/vb6_event_callbacks.asp)

```vb
Dim WithEvents myZipcrc As ChilkatZipCrc

Private Sub myZipcrc_AbortCheck(abort As Long)

	'Insert application code here.

End Sub
```

### ZipCrc.PercentDone (event)

`Chilkat 11.7.0 · activex · ZipCrc · PercentDone · event`

```
PercentDone(ByVal pctDone As Long, abort As Long)
```

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 `1`. This will cause the method to terminate and return a failure status or corresponding failure value.

**VB6 Event callback implementation:**

**Important:** Event callbacks from ***asynchronous method calls*** are generally not possible from the ActiveX. See [VB6 Event Callbacks](https://www.chilkatsoft.com/vb6_event_callbacks.asp)

```vb
Dim WithEvents myZipcrc As ChilkatZipCrc

Private Sub myZipcrc_PercentDone(ByVal pctDone As Long, abort As Long)

	'Insert application code here.

End Sub
```

### ZipCrc.ProgressInfo (event)

`Chilkat 11.7.0 · activex · ZipCrc · ProgressInfo · event`

```
ProgressInfo(ByVal name As String, ByVal 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.

**VB6 Event callback implementation:**

**Important:** Event callbacks from ***asynchronous method calls*** are generally not possible from the ActiveX. See [VB6 Event Callbacks](https://www.chilkatsoft.com/vb6_event_callbacks.asp)

```vb
Dim WithEvents myZipcrc As ChilkatZipCrc

Private Sub myZipcrc_ProgressInfo(ByVal name As String, ByVal value As String)

	'Insert application code here.

End Sub
```

### ZipCrc.TaskCompleted (event)

`Chilkat 11.7.0 · activex · ZipCrc · TaskCompleted · event`

```
TaskCompleted(task As ChilkatTask)
```

Called from the background thread when an asynchronous task completes.

**VB6 Event callback implementation:**

**Important:** Event callbacks from ***asynchronous method calls*** are generally not possible from the ActiveX. See [VB6 Event Callbacks](https://www.chilkatsoft.com/vb6_event_callbacks.asp)

```vb
Dim WithEvents myZipcrc As ChilkatZipCrc

Private Sub myZipcrc_TaskCompleted(task As ChilkatTask)

	'Insert application code here.

End Sub
```

## Async variants

Each returns a `Task` instead of the result and takes the same arguments as the synchronous method; run the task, wait for `Finished`, then read the result from the task. No new Async methods are added from 11.7.0 on.

```
FileCrcAsync(path As String) As ChilkatTask
```

## Related classes

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