Java BitSet to bitsToHexString(BitSet ba, int size)

Description

Pack the bits in ba into a byte[] then convert that to a hex string and return it.

License

Open Source License

Declaration

public static String bitsToHexString(BitSet ba, int size) 

Method Source Code

//package com.java2s;
/*/*www  . j a v  a2s  .c o m*/
 *   This file is part of dhcp4java, a DHCP API for the Java language.
 *   (c) 2006 Stephan Hadinger
 *
 *   This library is free software; you can redistribute it and/or
 *   modify it under the terms of the GNU Lesser General Public
 *   License as published by the Free Software Foundation; either
 *   version 2.1 of the License, or (at your option) any later version.
 *
 *   This library 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
 *   Lesser General Public License for more details.
 *
 *   You should have received a copy of the GNU Lesser General Public
 *   License along with this library; if not, write to the Free Software
 *   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 */

import java.util.BitSet;

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

    /**
     * Converts a byte array into a string of upper case hex chars.
     *
     *  <at> param bs
     *            A byte array
     *  <at> param off
     *            The index of the first byte to read
     *  <at> param length
     *            The number of bytes to read.
     *  <at> return the string of hex chars.
     */
    public static String bytesToHex(byte[] bs, int off, int length) {
        StringBuffer sb = new StringBuffer(length * 2);
        bytesToHexAppend(bs, off, length, sb);
        return sb.toString();
    }

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

    /**
     * Pack the bits in ba into a byte[].
     */
    public static byte[] bitsToBytes(BitSet ba, int size) {
        int bytesAlloc = countBytesForBits(size);
        byte[] b = new byte[bytesAlloc];

        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 && ba.get(idx));

                s |= (val ? (1 << j) : 0);
            }

            if (s > 255) {
                throw new IllegalStateException("WTF? s = " + s);
            }

            b[i] = (byte) s;
        }
        return b;
    }

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

    /**
     *  <at> 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);
    }
}

Related

1. bitSetToLong(BitSet set)
2. bitSetToMap(Map map, String key, BitSet bits, int length)
3. bitSetToUnsignedInt(BitSet b, int startBit, int length)
4. bitsToBytes(BitSet ba, int size)
5. BitsToBytes(BitSet bits)
6. BitsToInt(BitSet bits, int length)
7. convert(BitSet bits)
8. convert(BitSet bits)