This is an I2P port of snark [http://klomp.org/snark], a GPL'ed bittorrent client

The build in tracker has been removed for simplicity.

Example usage:
  java -jar lib/i2psnark.jar myFile.torrent

or, a more verbose setting:
  java -jar lib/i2psnark.jar --eepproxy 127.0.0.1 4444 \
       --i2cp 127.0.0.1 7654 "inbound.length=2 outbound.length=2" \
       --debug 6 myFile.torrent

apps/i2psnark/java/src/org/klomp/snark/BitField.java

@@ -0,0 +1,131 @@
+/* BitField - Container of a byte array representing set and unset bits.
+   Copyright (C) 2003 Mark J. Wielaard
+
+   This file is part of Snark.
+   
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+ 
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+ 
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software Foundation,
+   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+*/
+
+package org.klomp.snark;
+
+import java.util.Iterator;
+import java.util.Set;
+import java.util.HashSet;
+
+/**
+ * Container of a byte array representing set and unset bits.
+ */
+public class BitField
+{
+
+  private final byte[] bitfield;
+  private final int size;
+
+  /**
+   * Creates a new BitField that represents <code>size</code> unset bits.
+   */
+  public BitField(int size)
+  {
+    this.size = size;
+    int arraysize = ((size-1)/8)+1;
+    bitfield = new byte[arraysize];
+  }
+
+  /**
+   * Creates a new BitField that represents <code>size</code> bits
+   * as set by the given byte array. This will make a copy of the array.
+   * Extra bytes will be ignored.
+   *
+   * @exception ArrayOutOfBoundsException if give byte array is not large
+   * enough.
+   */
+  public BitField(byte[] bitfield, int size)
+  {
+    this.size = size;
+    int arraysize = ((size-1)/8)+1;
+    this.bitfield = new byte[arraysize];
+    
+    // XXX - More correct would be to check that unused bits are
+    // cleared or clear them explicitly ourselves.
+    System.arraycopy(bitfield, 0, this.bitfield, 0, arraysize);
+  }
+
+  /**
+   * This returns the actual byte array used.  Changes to this array
+   * effect this BitField.  Note that some bits at the end of the byte
+   * array are supposed to be always unset if they represent bits
+   * bigger then the size of the bitfield.
+   */
+  public byte[] getFieldBytes()
+  {
+    return bitfield;
+  }
+
+  /**
+   * Return the size of the BitField. The returned value is one bigger
+   * then the last valid bit number (since bit numbers are counted
+   * from zero).
+   */
+  public int size()
+  {
+    return size;
+  }
+
+  /**
+   * Sets the given bit to true.
+   *
+   * @exception IndexOutOfBoundsException if bit is smaller then zero
+   * bigger then size (inclusive).
+   */
+  public void set(int bit)
+  {
+    if (bit < 0 || bit >= size)
+      throw new IndexOutOfBoundsException(Integer.toString(bit));
+    int index = bit/8;
+    int mask = 128 >> (bit % 8);
+    bitfield[index] |= mask;
+  }
+
+  /**
+   * Return true if the bit is set or false if it is not.
+   *
+   * @exception IndexOutOfBoundsException if bit is smaller then zero
+   * bigger then size (inclusive).
+   */
+  public boolean get(int bit)
+  {
+    if (bit < 0 || bit >= size)
+      throw new IndexOutOfBoundsException(Integer.toString(bit));
+
+    int index = bit/8;
+    int mask = 128 >> (bit % 8);
+    return (bitfield[index] & mask) != 0;
+  }
+
+  public String toString()
+  {
+    // Not very efficient
+    StringBuffer sb = new StringBuffer("BitField[");
+    for (int i = 0; i < size; i++)
+      if (get(i))
+        {
+          sb.append(' ');
+          sb.append(i);
+        }
+    sb.append(" ]");
+
+    return sb.toString();
+  }
+}