erasurecodec.java

pastry的java实现的2.0b版

/*************************************************************************

"FreePastry" Peer-to-Peer Application Development Substrate 

Copyright 2002, Rice University. All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
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- Redistributions of source code must retain the above copyright
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- Redistributions in binary form must reproduce the above copyright
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documentation and/or other materials provided with the distribution.

- Neither  the name  of Rice  University (RICE) nor  the names  of its
contributors may be  used to endorse or promote  products derived from
this software without specific prior written permission.

This software is provided by RICE and the contributors on an "as is"
basis, without any representations or warranties of any kind, express
or implied including, but not limited to, representations or
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particular purpose. In no event shall RICE or contributors be liable
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consequential damages (including, but not limited to, procurement of
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whether in contract, strict liability, or tort (including negligence
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********************************************************************************/
package rice.p2p.glacier;

import java.io.*;
import java.util.Arrays;

import rice.environment.Environment;
import rice.environment.logging.*;
import rice.environment.random.RandomSource;
import rice.environment.random.simple.SimpleRandomSource;
import rice.p2p.commonapi.Endpoint;
import rice.p2p.past.PastContent;
import rice.p2p.past.rawserialization.*;
import rice.p2p.util.rawserialization.*;

/**
 * DESCRIBE THE CLASS
 *
 * @version $Id: ErasureCodec.java 3274 2006-05-15 16:17:47Z jeffh $
 * @author ahae
 */
public class ErasureCodec {

  /**
   * DESCRIBE THE FIELD
   */
  protected int numFragments;
  /**
   * DESCRIBE THE FIELD
   */
  protected int numSurvivors;

  /**
   * DESCRIBE THE FIELD
   */
  protected Environment environment;
  /**
   * DESCRIBE THE FIELD
   */
  protected Logger logger;

  final static int Lfield = 10;
  final static int MultField = (1 << Lfield) - 1;

  static int[] ExpToFieldElt;
  static int[] FieldEltToExp;
  static boolean isEltInitialized = false;

  /**
   * Constructor for ErasureCodec.
   *
   * @param _numFragments DESCRIBE THE PARAMETER
   * @param _numSurvivors DESCRIBE THE PARAMETER
   * @param env DESCRIBE THE PARAMETER
   */
  public ErasureCodec(int _numFragments, int _numSurvivors, Environment env) {
    environment = env;
    logger = environment.getLogManager().getLogger(getClass(), null);
    numFragments = _numFragments;
    numSurvivors = _numSurvivors;

    if (!isEltInitialized) {
      initElt();
    }
  }

  /**
   * DESCRIBE THE METHOD
   *
   * @param data DESCRIBE THE PARAMETER
   */
  public void dump(byte[] data) {
    String hex = "0123456789ABCDEF";
    String s = "";
    for (int i = 0; i < data.length; i++) {
      int d = data[i];
      if (d < 0) {
        d += 256;
      }
      int hi = (d >> 4);
      int lo = (d & 15);

      s += hex.charAt(hi) + "" + hex.charAt(lo);
      if (((i % 16) == 15) || (i == (data.length - 1))) {
        s += "\n";
      } else {
        s += " ";
      }
    }
    if (logger.level <= Logger.INFO) {
      logger.log(
        s);
    }
  }

  /**
   * DESCRIBE THE METHOD
   *
   * @param obj DESCRIBE THE PARAMETER
   * @param generateFragment DESCRIBE THE PARAMETER
   * @return DESCRIBE THE RETURN VALUE
   */
  public Fragment[] encodeObject(PastContent obj, boolean[] generateFragment) {
    return encodeObject(obj instanceof RawPastContent ? (RawPastContent) obj : new JavaSerializedPastContent(obj), generateFragment);
  }

  /**
   * Serializes the object.
   *
   * @param obj
   * @param generateFragment
   * @return
   */
  public Fragment[] encodeObject(RawPastContent obj, boolean[] generateFragment) {
    if (logger.level <= Logger.FINER) {
      logger.log(
        "Serialize object: " + obj);
    }

    try {
      SimpleOutputBuffer sob = new SimpleOutputBuffer();
      sob.writeShort(obj.getType());
      obj.serialize(sob);
      return encode(sob.getBytes(), sob.getWritten(), generateFragment);
    } catch (IOException ioe) {
      if (logger.level <= Logger.WARNING) {
        logger.log(
          "Cannot serialize object: " + ioe);
      }
      return null;
    }
  }


//  public Fragment[] encodeObject(PastContent obj, boolean[] generateFragment) {
//    byte bytes[];
//
//    try {
//      ByteArrayOutputStream byteStream = new ByteArrayOutputStream();
//      ObjectOutputStream objectStream = new ObjectOutputStream(byteStream);
//
//      objectStream.writeObject(obj);
//      objectStream.flush();
//
//      bytes = byteStream.toByteArray();
//    } catch (IOException ioe) {
//      if (logger.level <= Logger.WARNING) logger.logException(
//          "encodeObject: ", ioe);
//      return null;
//    }
//
//    return encode(bytes, generateFragment);
//  }

  /**
   * Input: buffer of size <numFragments*Lfield>; first <numSurvivors*Lfield>
   * words contain message, rest is zeroes Output: buffer contains fragments
   *
   * @param buffer DESCRIBE THE PARAMETER
   */
  protected void encodeChunk(int[] buffer) {
    for (int row = 0; row < (numFragments - numSurvivors); row++) {
      for (int col = 0; col < numSurvivors; col++) {
        int exponent = (MultField - FieldEltToExp[(row ^ col) ^ (1 << (Lfield - 1))]) % MultField;
        for (int row_bit = 0; row_bit < Lfield; row_bit++) {
          for (int col_bit = 0; col_bit < Lfield; col_bit++) {
            if ((ExpToFieldElt[exponent + row_bit] & (1 << col_bit)) != 0) {
              buffer[numSurvivors * Lfield + row * Lfield + row_bit] ^= buffer[col_bit + col * Lfield];
            }
          }
        }
      }
    }
  }

  /**
   * Generates multiple fragments from the incoming bytes
   *
   * @param bytes
   * @param length
   * @param generateFragment
   * @return
   */
  public Fragment[] encode(byte[] bytes, int length, boolean[] generateFragment) {
    int wantFragments = 0;
    for (int i = 0; i < generateFragment.length; i++) {
      if (generateFragment[i]) {
        wantFragments++;
      }
    }

    // System.outt.println(Systemm.currentTimeMillis()+" XXX before encode("+bytes.length+" bytes, "+wantFragments+" fragments) free="+Runtime.getRuntime().freeMemory()+" total="+Runtime.getRuntime().totalMemory());

    int numWords = (length + 3) / 4;
    int wordsPerGroup = (numSurvivors * Lfield);
    int numGroups = (numWords + (wordsPerGroup - 1)) / wordsPerGroup;
    int wordsPerFragment = numGroups * Lfield;
    int buffer[] = new int[numFragments * Lfield];
    Fragment frag[] = new Fragment[numFragments];

    for (int i = 0; i < numFragments; i++) {
      if (generateFragment[i]) {
        frag[i] = new Fragment(wordsPerFragment * 4);
      } else {
        frag[i] = null;
      }
    }

    //System.outt.println(bytes.length+" bytes => "+numFragments+" fragments with "+wordsPerFragment+" words ("+numGroups+" groups)");

    for (int g = 0; g < numGroups; g++) {
      int offset = g * wordsPerGroup * 4;
      int wordsHere = Math.min((length - offset + 3) / 4, wordsPerGroup);

      Arrays.fill(buffer, 0);
      for (int i = 0; i < wordsHere; i++) {
        byte b0 = (offset + 4 * i + 0 < length) ? bytes[offset + 4 * i + 0] : 0;
        byte b1 = (offset + 4 * i + 1 < length) ? bytes[offset + 4 * i + 1] : 0;
        byte b2 = (offset + 4 * i + 2 < length) ? bytes[offset + 4 * i + 2] : 0;
        byte b3 = (offset + 4 * i + 3 < length) ? bytes[offset + 4 * i + 3] : 0;
        buffer[i] = (b0 << 24) | ((b1 << 16) & 0xFF0000) | ((b2 << 8) & 0xFF00) | (b3 & 0xFF);
      }

      encodeChunk(buffer);

      for (int i = 0; i < numFragments; i++) {
        if (generateFragment[i]) {
          for (int j = 0; j < Lfield; j++) {
            frag[i].payload[4 * (g * Lfield + j) + 0] = (byte) ((buffer[i * Lfield + j]) & 0xFF);
            frag[i].payload[4 * (g * Lfield + j) + 1] = (byte) ((buffer[i * Lfield + j] >> 8) & 0xFF);
            frag[i].payload[4 * (g * Lfield + j) + 2] = (byte) ((buffer[i * Lfield + j] >> 16) & 0xFF);
            frag[i].payload[4 * (g * Lfield + j) + 3] = (byte) ((buffer[i * Lfield + j] >> 24) & 0xFF);
          }
        }
      }
    }

    // System.out.println(Systemm.currentTimeMillis()+" XXX after encode("+bytes.length+" bytes, "+wantFragments+" fragments) free="+Runtime.getRuntime().freeMemory()+" total="+Runtime.getRuntime().totalMemory());

    return frag;
  }

  /**
   * DESCRIBE THE METHOD
   *
   * @param buffer DESCRIBE THE PARAMETER
   * @param nExtra DESCRIBE THE PARAMETER
   * @param RowInd DESCRIBE THE PARAMETER
   * @param haveFragment DESCRIBE THE PARAMETER
   * @param InvMat DESCRIBE THE PARAMETER
   * @param ColInd DESCRIBE THE PARAMETER
   */
  protected void decodeChunk(int[] buffer, int nExtra, int[] RowInd, boolean[] haveFragment, long[][] InvMat, int[] ColInd) {

    // *** Second last step ***

    int M[] = new int[(numFragments - numSurvivors) * Lfield];
    for (int i = 0; i < nExtra; i++) {
      for (int j = 0; j < Lfield; j++) {
        M[i * Lfield + j] = buffer[(RowInd[i] + numSurvivors) * Lfield + j];
      }
    }

    for (int row = 0; row < nExtra; row++) {
      for (int col = 0; col < numSurvivors; col++) {
        if (haveFragment[col]) {
          int exponent = (MultField - FieldEltToExp[RowInd[row] ^ col ^ (1 << (Lfield - 1))]) % MultField;
          for (int row_bit = 0; row_bit < Lfield; row_bit++) {
            for (int col_bit = 0; col_bit < Lfield; col_bit++) {
              if ((ExpToFieldElt[exponent + row_bit] & (1 << col_bit)) != 0) {
                M[row_bit + row * Lfield] ^= buffer[col_bit + col * Lfield];
              }
            }
          }
        }