(Android™) Example: Hash Text in Chunks

Shows how to generate a final hash, like SHA-256, for a large text by processing it in chunks.

Chilkat Android™ Downloads Android™ Java Libraries Android C/C++ Libraries

// Important: Don't forget to include the call to System.loadLibrary
// as shown at the bottom of this code sample.
package com.test;

import android.app.Activity;
import com.chilkatsoft.*;

import android.widget.TextView;
import android.os.Bundle;

public class SimpleActivity extends Activity {

  private static final String TAG = "Chilkat";

  // Called when the activity is first created.
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    CkCrypt2 crypt = new CkCrypt2();
    crypt.put_HashAlgorithm("sha256");
    crypt.put_Charset("utf-8");

    CkBinData bd = new CkBinData();

    String s = "The quick brown fox jumped over the lazy dog.\r\n";

    // Accumulate the text in a StringBuilder.  We'll demonstrate hashing the text in chunks,
    // and then also hashing the entire text at once to show the results are the same.

    bd.AppendString(s,"utf-8");
    boolean success = crypt.HashBeginString(s);

    int i = 0;
    while (i < 200) {
        bd.AppendString(s,"utf-8");
        crypt.HashMoreString(s);
        i = i + 1;
        }

    // Get the hash in base64 format.
    crypt.put_EncodingMode("base64");

    String encodedHash = crypt.hashFinalENC();
    Log.i(TAG, "Hash computed in chunks: " + encodedHash);

    // Let's alternatively compute the hash of the entire amount of data at once,
    // to show the hash computation is the same:
    encodedHash = crypt.hashBdENC(bd);
    Log.i(TAG, "Hash computed in 1 step: " + encodedHash);

    // Output:

    // Hash computed in chunks: unwkVff61k40roRIJizaknreScHaL6frWe37kydXbZQ=
    // Hash computed in 1 step: unwkVff61k40roRIJizaknreScHaL6frWe37kydXbZQ=

  }

  static {
      System.loadLibrary("chilkat");

      // Note: If the incorrect library name is passed to System.loadLibrary,
      // then you will see the following error message at application startup:
      //"The application <your-application-name> has stopped unexpectedly. Please try again."
  }
}