Bytes.java

/*
 * Copyright (c) 1997-1999 The Java Apache Project.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
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 *    distribution.
 *
 * 3. All advertising materials mentioning features or use of this
 *    software must display the following acknowledgment:
 *    "This product includes software developed by the Java Apache 
 *    Project for use in the Apache JServ servlet engine project
 *    <http://java.apache.org/>."
 *
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 *    derived from this software without prior written permission.
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 * 5. Products derived from this software may not be called "Apache JServ"
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 *    acknowledgment:
 *    "This product includes software developed by the Java Apache 
 *    Project for use in the Apache JServ servlet engine project
 *    <http://java.apache.org/>."
 *    
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 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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import java.io.*;

/**
 * Static methods for managing byte arrays
 * (all methods follow Big Endian order
 * where most significant bits are in front).
 *
 * @author <a href="mailto:stefano@apache.org">Stefano Mazzocchi</a>
 * @author Ben Chun
 * @version 1.8 (added toFloat and toDouble methods)
 */
public class Bytes {

    /**
     * Build an int from first 4 bytes of the array.
     *
     * @param b    the byte array to convert.
     */
    public static int toInt(byte[] b) {
        return (((int) b[3]) & 0xFF) +
               ((((int) b[2]) & 0xFF) << 8) +
               ((((int) b[1]) & 0xFF) << 16) +
               ((((int) b[0]) & 0xFF) << 24);
    }

    /**
     * Build a long from first 8 bytes of the array.
     *
     * @param b    the byte array to convert.
     */
    public static long toLong(byte[] b) {
        return (((long) b[7]) & 0xFF) +
               ((((long) b[6]) & 0xFF) << 8) +
               ((((long) b[5]) & 0xFF) << 16) +
               ((((long) b[4]) & 0xFF) << 24) +
               ((((long) b[3]) & 0xFF) << 32) +
               ((((long) b[2]) & 0xFF) << 40) +
               ((((long) b[1]) & 0xFF) << 48) +
               ((((long) b[0]) & 0xFF) << 56);
    }

    /**
     * Build a float from the first 4 bytes of the array.
     *
     * @param b    the byte array to convert.
     */
    public static float toFloat(byte[] b) {
	int i = toInt( b ) ;
	return Float.intBitsToFloat( i ) ;
    }
    
    /**
     * Build a double-precision float from the first 8 bytes of the array.
     *
     * @param b    the byte array to convert.
     */
    public static double toDouble(byte[] b) {
	long l = toLong( b );
	return Double.longBitsToDouble( l ) ;
    }


    /**
     * Returns a 4-byte array built from an int.
     *
     * @param  n  the number to convert.
     */
    public static byte[] toBytes(int n) {
        return toBytes(n, new byte[4]);
    }


    /**
     * Build a 4-byte array from an int.
     * No check is performed on the array length.
     *
     * @param  n  the number to convert.
     * @param  b  the array to fill.
     */
    public static byte[] toBytes(int n, byte[] b) {
        b[3] = (byte) (n);
        n >>>= 8;
        b[2] = (byte) (n);
        n >>>= 8;
        b[1] = (byte) (n);
        n >>>= 8;
        b[0] = (byte) (n);

        return b;
    }

    /**
     * Returns a 8-byte array built from a long.
     *
     * @param  n  the number to convert.
     */
    public static byte[] toBytes(long n) {
        return toBytes(n, new byte[8]);
    }

    /**
     * Build a 8-byte array from a long.
     * No check is performed on the array length.
     *
     * @param  n  the number to convert.
     * @param  b  the array to fill.
     */
    public static byte[] toBytes(long n, byte[] b) {
        b[7] = (byte) (n);
        n >>>= 8;
        b[6] = (byte) (n);
        n >>>= 8;
        b[5] = (byte) (n);
        n >>>= 8;
        b[4] = (byte) (n);
        n >>>= 8;
        b[3] = (byte) (n);
        n >>>= 8;
        b[2] = (byte) (n);
        n >>>= 8;
        b[1] = (byte) (n);
        n >>>= 8;
        b[0] = (byte) (n);

        return b;
    }

    /**
     * Compares two byte arrays for equality.
     *
     * @return true if the arrays have identical contents
     */
    public static boolean areEqual(byte[] a, byte[] b) {
        int aLength = a.length;
        if (aLength != b.length) return false;

        for (int i = 0; i < aLength; i++)
            if (a[i] != b[i]) return false;

        return true;
    }

    /**
     * Appends two bytes array into one.
     */
    public static byte[] append(byte[] a, byte[] b) {
        byte[] z = new byte[a.length + b.length];
        System.arraycopy(a, 0, z, 0, a.length);
        System.arraycopy(b, 0, z, a.length, b.length);
        return z;
    }

    /**
     * Appends three bytes array into one.
     */
    public static byte[] append(byte[] a, byte[] b, byte[] c) {
        byte[] z = new byte[a.length + b.length + c.length];
        System.arraycopy(a, 0, z, 0, a.length);
        System.arraycopy(b, 0, z, a.length, b.length);
        System.arraycopy(c, 0, z, a.length + b.length, c.length);
        return z;
    }

    /**
     * Gets the end of the byte array given.
     * @param b byte array
     * @param pos the position from which to start
     * @return a byte array consisting of the portion of b between pos and
     * the end of b.
     */
    public static byte[] copy(byte[] b, int pos) {
        return copy(b, pos, b.length - pos);
    }

    /**
     * Gets a sub-set of the byte array given.
     * @param b byte array
     * @param pos the position from which to start
     * @param length the number of bytes to copy from the original byte array
     * to the new one.
     * @return a byte array consisting of the portion of b starting at pos
     * and continuing for length bytes, or until the end of b is reached,
     * which ever occurs first.
     */
    public static byte[] copy(byte[] b, int pos, int length) {
        byte[] z = new byte[length];
        System.arraycopy(b, pos, z, 0, length);
        return z;
    }

    /**
     * Merges a bytes array into another starting from the
     * given positions.
     */
    public static void merge(byte[] src, byte[] dest, int srcpos, int destpos, int length) {
        System.arraycopy(src, srcpos, dest, destpos, length);
    }

    /**
     * Merges a bytes array into another starting from the
     * given position.
     */
    public static void merge(byte[] src, byte[] dest, int pos) {
        System.arraycopy(src, 0, dest, pos, src.length);
    }

    /**
     * Merges a bytes array into another.
     */
    public static void merge(byte[] src, byte[] dest) {
        System.arraycopy(src, 0, dest, 0, src.length);
    }

    /**
     * Merges a bytes array into another starting from the
     * given position.
     */
    public static void merge(byte[] src, byte[] dest, int pos, int length) {
        System.arraycopy(src, 0, dest, pos, length);
    }

    private static final char[] hexDigits = {
        '0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'
    };

    /**
     * Returns a string of hexadecimal digits from a byte array,
     * starting at offset and continuing for length bytes.
     */
    public static String toString(byte[] b, int offset, int length) {
        char[] buf = new char[length * 2];

        for (int i = offset, j = 0, k; i < offset + length; i++) {
            k = b[i];
            buf[j++] = hexDigits[(k >>> 4) & 0x0F];
            buf[j++] = hexDigits[k & 0x0F];
        }

        return new String(buf);
    }

    /**
     * Returns a string of hexadecimal digits from a byte array..
     */
    public static String toString(byte[] b) {
        return toString(b, 0, b.length);
    }
}