Number in hexadecimal format are used throughout Freenet. : Hexadecimal « Data Type « Java

1. Java
2. Data Type
3. Hexadecimal

Number in hexadecimal format are used throughout Freenet.

      
//package freenet.support;

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.math.BigInteger;
import java.util.BitSet;

/**
 * Number in hexadecimal format are used throughout Freenet.
 * 
 * <p>Unless otherwise stated, the conventions follow the rules outlined in the 
 * Java Language Specification.</p>
 * 
 * @author syoung
 */
public class HexUtil {
  /**
   * Converts a byte array into a string of lower case hex chars.
   * 
   * @param bs
   *            A byte array
   * @param off
   *            The index of the first byte to read
   * @param length
   *            The number of bytes to read.
   * @return the string of hex chars.
   */
  public static final String bytesToHex(byte[] bs, int off, int length) {
    if (bs.length <= off || bs.length < off+length)
      throw new IllegalArgumentException();
    StringBuilder sb = new StringBuilder(length * 2);
    bytesToHexAppend(bs, off, length, sb);
    return sb.toString();
  }

  public static final void bytesToHexAppend(
    byte[] bs,
    int off,
    int length,
    StringBuilder sb) {
    if (bs.length <= off || bs.length < off+length)
      throw new IllegalArgumentException();
    sb.ensureCapacity(sb.length() + length * 2);
    for (int i = off; i < (off + length); i++) {
      sb.append(Character.forDigit((bs[i] >>> 4) & 0xf, 16));
      sb.append(Character.forDigit(bs[i] & 0xf, 16));
    }
  }

  public static final String bytesToHex(byte[] bs) {
    return bytesToHex(bs, 0, bs.length);
  }

  public static final byte[] hexToBytes(String s) {
    return hexToBytes(s, 0);
  }

  public static final byte[] hexToBytes(String s, int off) {
    byte[] bs = new byte[off + (1 + s.length()) / 2];
    hexToBytes(s, bs, off);
    return bs;
  }

  /**
   * Converts a String of hex characters into an array of bytes.
   * 
   * @param s
   *            A string of hex characters (upper case or lower) of even
   *            length.
   * @param out
   *            A byte array of length at least s.length()/2 + off
   * @param off
   *            The first byte to write of the array
   */
  public static final void hexToBytes(String s, byte[] out, int off)
    throws NumberFormatException, IndexOutOfBoundsException {
    
    int slen = s.length();
    if ((slen % 2) != 0) {
      s = '0' + s;
    }

    if (out.length < off + slen / 2) {
      throw new IndexOutOfBoundsException(
        "Output buffer too small for input ("
          + out.length
          + '<'
                        + off
          + slen / 2
          + ')');
    }

    // Safe to assume the string is even length
    byte b1, b2;
    for (int i = 0; i < slen; i += 2) {
      b1 = (byte) Character.digit(s.charAt(i), 16);
      b2 = (byte) Character.digit(s.charAt(i + 1), 16);
      if ((b1 < 0) || (b2 < 0)) {
        throw new NumberFormatException();
      }
      out[off + i / 2] = (byte) (b1 << 4 | b2);
    }
  }

  /**
   * Pack the bits in ba into a byte[].
   *
   * @param ba : the BitSet
   * @param size : How many bits shall be taken into account starting from the LSB?
   */
  public final static byte[] bitsToBytes(BitSet ba, int size) {
    int bytesAlloc = countBytesForBits(size);
    byte[] b = new byte[bytesAlloc];
    StringBuilder sb =null;
    
    for(int i=0;i<b.length;i++) {
      short s = 0;
      for(int j=0;j<8;j++) {
        int idx = i*8+j;
        boolean val = 
          idx > size - 1 ? false :
            ba.get(idx);
        s |= val ? (1<<j) : 0;
      }
      if(s > 255) throw new IllegalStateException("WTF? s = "+s);
      b[i] = (byte)s;
    }
    return b;
  }

  /**
   * Pack the bits in ba into a byte[] then convert that
   * to a hex string and return it.
   */
  public final static String bitsToHexString(BitSet ba, int size) {
    return bytesToHex(bitsToBytes(ba, size));
  }


  /**
   * @return the number of bytes required to represent the
   * bitset
   */
  public static int countBytesForBits(int size) {
    // Brackets matter here! == takes precedence over the rest
    return (size/8) + ((size % 8) == 0 ? 0:1);
  }


  /**
   * Read bits from a byte array into a bitset
   * @param b the byte[] to read from
   * @param ba the bitset to write to
   */
  public static void bytesToBits(byte[] b, BitSet ba, int maxSize) {
    
    int x = 0;
    for(int i=0;i<b.length;i++) {
      for(int j=0;j<8;j++) {
        if(x > maxSize) break;
        int mask = 1 << j;
        boolean value = (mask & b[i]) != 0;
        ba.set(x, value);
        x++;
      }
    }
  }


  /**
   * Read a hex string of bits and write it into a bitset
   * @param s hex string of the stored bits
   * @param ba the bitset to store the bits in
   * @param length the maximum number of bits to store 
   */
  public static void hexToBits(String s, BitSet ba, int length) {
    byte[] b = hexToBytes(s);
    bytesToBits(b, ba, length);
  }
  
  /**
     * Write a (reasonably short) BigInteger to a stream.
     * @param integer the BigInteger to write
     * @param out the stream to write it to
     */
    public static void writeBigInteger(BigInteger integer, DataOutputStream out) throws IOException {
        if(integer.signum() == -1) {
            //dump("Negative BigInteger", Logger.ERROR, true);
            throw new IllegalStateException("Negative BigInteger!");
        }
        byte[] buf = integer.toByteArray();
        if(buf.length > Short.MAX_VALUE)
            throw new IllegalStateException("Too long: "+buf.length);
        out.writeShort((short)buf.length);
        out.write(buf);
    }

    /**
   * Read a (reasonably short) BigInteger from a DataInputStream
   * @param dis the stream to read from
   * @return a BigInteger
   */
  public static BigInteger readBigInteger(DataInputStream dis) throws IOException {
      short i = dis.readShort();
      if(i < 0) throw new IOException("Invalid BigInteger length: "+i);
      byte[] buf = new byte[i];
      dis.readFully(buf);
      return new BigInteger(1,buf);
  }


    /**
     * Turn a BigInteger into a hex string.
     * BigInteger.toString(16) NPEs on Sun JDK 1.4.2_05. :<
     * The bugs in their Big* are getting seriously irritating...
     */
    public static String biToHex(BigInteger bi) {
        return bytesToHex(bi.toByteArray());
    }
}

   
    
    
    
    
    
  

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