CkZipCrc Java Reference Documentation

CkZipCrc

Calculate a Zip CRC checksum for a file or in-memory data.

Object Creation

CkZipCrc obj = new CkZipCrc();

Properties

boolean get_LastMethodSuccess();
void put_LastMethodSuccess(boolean newVal);

Introduced in version 9.5.0.52

Indicate whether the last method call succeeded or failed. A value of true indicates success, a value of false indicates failure. This property is automatically set for method calls. It is not modified by property accesses. The property is automatically set to indicate success for the following types of method calls:

  • Any method that returns a string.
  • Any method returning a Chilkat object, binary bytes, or a date/time.
  • Any method returning a standard boolean status value where success = true and failure = false.
  • Any method returning an integer where failure is defined by a return value less than zero.

Note: Methods that do not fit the above requirements will always set this property equal to true. For example, a method that returns no value (such as a "void" in C++) will technically always succeed.

Methods

void 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.

int CalculateCrc(CkByteData data);

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.

int EndStream();

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

int FileCrc(String path);

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.

CkTask FileCrcAsync(String path);

Creates an asynchronous task to call the FileCrc method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.

Returns nil on failure

(Android™) How to Run an Asynchronous Task

(Java) How to Run an Asynchronous Task

void MoreData(CkByteData data);

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

boolean ToHex(int crc, CkString outStr);
String toHex(int crc);

Converts a 32-bit integer to a hex string.

Returns true for success, false for failure.

Events

Chilkat supports event callbacks in Java (including Android) starting in version 9.5.0.52. To implement an event callback, your application would define and implement a class that derives from CkBaseProgress. Your application can implement methods to override some or all of the default/empty method implementations of the CkBaseProgress base class.

For example:

// Install an event callback handler to get progress events.
MyBaseProgress zipcrcProgress = new MyBaseProgress();
http.put_EventCallbackObject(zipcrcProgress);

MyBaseProgress example:

import com.chilkatsoft.CkBaseProgress;
import com.chilkatsoft.CkTask;

public class MyBaseProgress extends CkBaseProgress 
{	
  public boolean AbortCheck()
  {
    System.out.println("AbortCheck");
    // Return true to abort, false to allow the method to continue.
    return false;
  }
  	
  // pctDone is a value from 0 to 100
  // (it is actually value from 0 to the PercentDoneScale property setting)
  public boolean PercentDone(int pctDone)
  {
    System.out.println(pctDone);
    // Return true to abort, false to allow the method to continue.
    // Note: A PercentDone event is the equivalent of an AbortCheck.  
    // When PercentDone events are frequently firing, AbortCheck events are suppressed.
    // AbortCheck events will fire when the time between PercentDone events is longer 
    // than the HeartbeatMs property setting.
    return false;
  }
  
  public void ProgressInfo(String name, String value)
  {
    System.out.println(name + ": " + value);
  }
  
  public void TaskCompleted(CkTask task)
  {
     System.out.println("task completed!");
  }
  
}

public boolean AbortCheck();

Provides the opportunity for a method call to be aborted. The AbortCheck event is fired periodically based on the value of the HeartbeatMs property. If HeartbeatMs is 0, then no AbortCheck events will fire. As an example, to fire 5 AbortCheck events per second, set the HeartbeatMs property equal to 200. Return true to abort; return false to continue (not abort)

public boolean PercentDone(int pctDone);

Provides the percentage completed for any method that involves network communications or time-consuming processing (assuming it is a method where a percentage completion can be measured). This event is only fired when it is possible to know a percentage completion, and when it makes sense to express the operation as a percentage completed. The pctDone argument will have a value from 1 to 100. For operations (Chilkat method calls) that complete very quickly, the number of PercentDone callbacks will vary, but the final callback should have a value of 100. For long running operations, no more than one callback per percentage point will occur (for example: 1, 2, 3, ... 98, 99, 100).

The PercentDone callback counts as an AbortCheck event. For method calls that complete quickly such that PercentDone events fire, it may be that AbortCheck events don't fire because the opportunity to abort is already provided in the PercentDone callback. For time consuming operations, where the amount of time between PercentDone callbacks are long, AbortCheck callbacks may be used to allow for the operation to be aborted in a more responsive manner.

Return true to abort; return false to continue (not abort)

public void ProgressInfo(String name, String value);

A general name/value event that provides information about what is happening during a method call. To find out what information is available, write code to handle this event and log the name/value pairs. Most are self-explanatory.

public void TaskCompleted(CkTask task);

Called in the background thread when an asynchronous task completes.

public void TextData(String data);

Text data provided by certain methods.