content: /*******************************************************************************
   * Software Name : RCS IMS Stack
   *
   * Copyright (C) 2010-2016 Orange.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   ******************************************************************************/
  
  package com.gsma.rcs.core.ims.security;
  
  /**
   * base implementation of MD4 family style digest as outlined in "Handbook of Applied Cryptography",
   * pages 344 - 347.
   */
  public abstract class GeneralDigest implements Digest {
      private byte[] xBuf;
      private int xBufOff;
  
      private long byteCount;
  
      /**
       * Standard constructor
       */
      protected GeneralDigest() {
          xBuf = new byte[4];
          xBufOff = 0;
      }
  
      /**
       * Copy constructor. We are using copy constructors in place of the Object.clone() interface as
       * this interface is not supported by J2ME.
       */
      protected GeneralDigest(GeneralDigest t) {
          xBuf = new byte[t.xBuf.length];
          System.arraycopy(t.xBuf, 0, xBuf, 0, t.xBuf.length);
  
          xBufOff = t.xBufOff;
          byteCount = t.byteCount;
      }
  
      public void update(byte in) {
          xBuf[xBufOff++] = in;
  
          if (xBufOff == xBuf.length) {
              processWord(xBuf, 0);
              xBufOff = 0;
          }
  
          byteCount++;
      }
  
      public void update(byte[] in, int inOff, int len) {
          //
          // fill the current word
          //
          while ((xBufOff != 0) && (len > 0)) {
              update(in[inOff]);
  
              inOff++;
              len--;
          }
  
          //
          // process whole words.
          //
          while (len > xBuf.length) {
              processWord(in, inOff);
  
              inOff += xBuf.length;
              len -= xBuf.length;
              byteCount += xBuf.length;
          }
  
          //
          // load in the remainder.
          //
          while (len > 0) {
              update(in[inOff]);
  
              inOff++;
              len--;
          }
      }
  
      public void finish() {
          long bitLength = (byteCount << 3);
  
          //
          // add the pad bytes.
          //
          update((byte) 128);
  
          while (xBufOff != 0) {
              update((byte) 0);
          }
  
          processLength(bitLength);
  
          processBlock();
      }
  
      public void reset() {
          byteCount = 0;
  
          xBufOff = 0;
          for (int i = 0; i < xBuf.length; i++) {
              xBuf[i] = 0;
          }
      }
  
      protected abstract void processWord(byte[] in, int inOff);
  
      protected abstract void processLength(long bitLength);
  
      protected abstract void processBlock();
  }
  