ByteUtil.java

/*
 * Digital Audio Access Protocol (DAAP) Library
 * Copyright (C) 2004-2010 Roger Kapsi
 *
 * 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 org.ardverk.daap;

/**
 * Miscellaneous Java primitive to byte array and vice versa methods.
 * 
 * <p>
 * Note: All values are in Big-Endian!
 * </p>
 * 
 * @author Roger Kapsi
 */
public final class ByteUtil {

    private ByteUtil() {
    }

    /**
     * 16bit to int
     */
    public static final int toInt16BE(byte[] src, int offset) {
        return (((src[offset] & 0xFF) << 8) + (src[++offset] & 0xFF));
    }

    /**
     * int to 16bit
     */
    public static final int toByte16BE(int value, byte[] dst, int offset) {
        dst[offset] = (byte) ((value >> 8) & 0xFF);
        dst[++offset] = (byte) (value & 0xFF);
        return 2;
    }

    /**
     * 32bit to int
     */
    public static final int toIntBE(byte[] src, int offset) {
        return (((src[offset] & 0xFF) << 24) + ((src[++offset] & 0xFF) << 16)
                + ((src[++offset] & 0xFF) << 8) + (src[++offset] & 0xFF));
    }

    /**
     * Copies the first 4 characters of fourChars to dst
     */
    public static final int toFourCharBytes(String fourChars, byte[] dst,
            int offset) throws IllegalArgumentException {

        final int length = fourChars.length();

        if (length > 4)
            throw new IllegalArgumentException("Illegal fourChars length: "
                    + length);

        for (int i = 0; i < length; i++) {
            dst[offset++] = (byte) (fourChars.charAt(i) & 0xFF);
        }

        return 4;
    }

    /**
     * This method converts the first 4 characters of fourChars to an integer.
     */
    public static final int toFourCharCode(String fourChars)
            throws IllegalArgumentException {

        final byte[] dst = new byte[4];
        toFourCharBytes(fourChars, dst, 0);
        return toIntBE(dst, 0);
    }

    /**
     * int to 32bit
     */
    public static final int toByteBE(int value, byte[] dst, int offset) {
        dst[offset] = (byte) ((value >> 24) & 0xFF);
        dst[++offset] = (byte) ((value >> 16) & 0xFF);
        dst[++offset] = (byte) ((value >> 8) & 0xFF);
        dst[++offset] = (byte) (value & 0xFF);
        return 4;
    }

    /**
     * long to 64bit
     */
    public static final int toByte64BE(long value, byte[] dst, int offset) {
        dst[offset] = (byte) ((value >> 56) & 0xFF);
        dst[++offset] = (byte) ((value >> 48) & 0xFF);
        dst[++offset] = (byte) ((value >> 40) & 0xFF);
        dst[++offset] = (byte) ((value >> 32) & 0xFF);
        dst[++offset] = (byte) ((value >> 24) & 0xFF);
        dst[++offset] = (byte) ((value >> 16) & 0xFF);
        dst[++offset] = (byte) ((value >> 8) & 0xFF);
        dst[++offset] = (byte) (value & 0xFF);
        return 8;
    }

    /**
     * 64bit to long
     */
    public static final long toLongBE(byte[] src, int offset) {
        return (((src[offset] & 0xFFl) << 56l)
                + ((src[++offset] & 0xFFl) << 48l)
                + ((src[++offset] & 0xFFl) << 40l)
                + ((src[++offset] & 0xFFl) << 32l)
                + ((src[++offset] & 0xFFl) << 24l)
                + ((src[++offset] & 0xFFl) << 16l)
                + ((src[++offset] & 0xFFl) << 8l) + (src[++offset] & 0xFFl));
    }
}