utility.java

《移动Agent技术》一书的所有章节源代码。

/*
 * @(#)Utility.java	1.5 98/01/12
 *
 * (C) Copyright Taligent, Inc. 1996, 1997 - All Rights Reserved
 * (C) Copyright IBM Corp. 1996, 1997 - All Rights Reserved
 *
 * Portions copyright (c) 1996 Sun Microsystems, Inc. All Rights Reserved.
 *
 *   The original version of this source code and documentation is copyrighted
 * and owned by Taligent, Inc., a wholly-owned subsidiary of IBM. These
 * materials are provided under terms of a License Agreement between Taligent
 * and Sun. This technology is protected by multiple US and International
 * patents. This notice and attribution to Taligent may not be removed.
 *   Taligent is a registered trademark of Taligent, Inc.
 *
 * Permission to use, copy, modify, and distribute this software
 * and its documentation for NON-COMMERCIAL purposes and without
 * fee is hereby granted provided that this copyright notice
 * appears in all copies. Please refer to the file "copyright.html"
 * for further important copyright and licensing information.
 *
 * SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF
 * THE SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
 * TO THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
 * PARTICULAR PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR
 * ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR
 * DISTRIBUTING THIS SOFTWARE OR ITS DERIVATIVES.
 *
 */
package java.text;

final class Utility {

    /**
     * Convenience utility to compare two Object[]s.
     * Ought to be in System
     */
    final static boolean arrayEquals(Object[] source, Object target) {
        if (source == null) return (target == null);
        if (!(target instanceof Object[])) return false;
        Object[] targ = (Object[]) target;
        return (source.length == targ.length
                && arrayRegionMatches(source, 0, targ, 0, source.length));
    }

    /**
     * Convenience utility to compare two int[]s
     * Ought to be in System
     */
    final static boolean arrayEquals(int[] source, Object target) {
        if (source == null) return (target == null);
        if (!(target instanceof int[])) return false;
        int[] targ = (int[]) target;
        return (source.length == targ.length
                && arrayRegionMatches(source, 0, targ, 0, source.length));
    }

    /**
     * Convenience utility to compare two double[]s
     * Ought to be in System
     */
    final static boolean arrayEquals(double[] source, Object target) {
        if (source == null) return (target == null);
        if (!(target instanceof double[])) return false;
        double[] targ = (double[]) target;
        return (source.length == targ.length
                && arrayRegionMatches(source, 0, targ, 0, source.length));
    }

    /**
     * Convenience utility to compare two Object[]s
     * Ought to be in System
     */
    final static boolean arrayEquals(Object source, Object target) {
        if (source == null) return (target == null);
        // for some reason, the correct arrayEquals is not being called
        // so do it by hand for now.
        if (source instanceof Object[])
            return(arrayEquals((Object[]) source,target));
        if (source instanceof int[])
            return(arrayEquals((int[]) source,target));
        if (source instanceof double[])
            return(arrayEquals((int[]) source,target));
        return source.equals(target);
    }

    /**
     * Convenience utility to compare two Object[]s
     * Ought to be in System.
     * @param len the length to compare.
     * The start indices and start+len must be valid.
     */
    final static boolean arrayRegionMatches(Object[] source, int sourceStart,
                                            Object[] target, int targetStart,
                                            int len)
    {
        int sourceEnd = sourceStart + len;
        int delta = targetStart - sourceStart;
        for (int i = sourceStart; i < sourceEnd; i++) {
            if (!arrayEquals(source[i],target[i + delta]))
            return false;
        }
        return true;
    }

    /**
     * Convenience utility to compare two int[]s.
     * @param len the length to compare.
     * The start indices and start+len must be valid.
     * Ought to be in System
     */
    final static boolean arrayRegionMatches(int[] source, int sourceStart,
                                            int[] target, int targetStart,
                                            int len)
    {
        int sourceEnd = sourceStart + len;
        int delta = targetStart - sourceStart;
        for (int i = sourceStart; i < sourceEnd; i++) {
            if (source[i] != target[i + delta])
            return false;
        }
        return true;
    }

    /**
     * Convenience utility to compare two arrays of doubles.
     * @param len the length to compare.
     * The start indices and start+len must be valid.
     * Ought to be in System
     */
    final static boolean arrayRegionMatches(double[] source, int sourceStart,
                                            double[] target, int targetStart,
                                            int len)
    {
        int sourceEnd = sourceStart + len;
        int delta = targetStart - sourceStart;
        for (int i = sourceStart; i < sourceEnd; i++) {
            if (source[i] != target[i + delta])
            return false;
        }
        return true;
    }

    /**
     * Convenience utility. Does null checks on objects, then calls equals.
     */
    final static boolean objectEquals(Object source, Object target) {
    if (source == null)
            return (target == null);
    else
            return source.equals(target);
    }

    /**
     * The ESCAPE character is used during run-length encoding.  It signals
     * a run of identical chars.
     */
    static final char ESCAPE = '\uA5A5';

    /**
     * The ESCAPE_BYTE character is used during run-length encoding.  It signals
     * a run of identical bytes.
     */
    static final byte ESCAPE_BYTE = (byte)0xA5;

    /**
     * Construct a string representing a short array.  Use run-length encoding.
     * A character represents itself, unless it is the ESCAPE character.  Then
     * the following notations are possible:
     *   ESCAPE ESCAPE   ESCAPE literal
     *   ESCAPE n c      n instances of character c
     * Since an encoded run occupies 3 characters, we only encode runs of 4 or
     * more characters.  Thus we have n > 0 and n != ESCAPE and n <= 0xFFFF.
     * If we encounter a run where n == ESCAPE, we represent this as:
     *   c ESCAPE n-1 c
     * The ESCAPE value is chosen so as not to collide with commonly
     * seen values.
     */
    static final String arrayToRLEString(short[] a) {
    StringBuffer buffer = new StringBuffer();
    // for (int i=0; i<a.length; ++i) buffer.append((char) a[i]);
    buffer.append((char) (a.length >> 16));
    buffer.append((char) a.length);
    short runValue = a[0];
    int runLength = 1;
    for (int i=1; i<a.length; ++i) {
        short s = a[i];
        if (s == runValue && runLength < 0xFFFF) ++runLength;
        else {
        encodeRun(buffer, runValue, runLength);
        runValue = s;
        runLength = 1;
        }
    }
    encodeRun(buffer, runValue, runLength);
    return buffer.toString();
    }

    /**
     * Construct a string representing a byte array.  Use run-length encoding.
     * Two bytes are packed into a single char, with a single extra zero byte at
     * the end if needed.  A byte represents itself, unless it is the
     * ESCAPE_BYTE.  Then the following notations are possible:
     *   ESCAPE_BYTE ESCAPE_BYTE   ESCAPE_BYTE literal
     *   ESCAPE_BYTE n b           n instances of byte b
     * Since an encoded run occupies 3 bytes, we only encode runs of 4 or
     * more bytes.  Thus we have n > 0 and n != ESCAPE_BYTE and n <= 0xFF.
     * If we encounter a run where n == ESCAPE_BYTE, we represent this as:
     *   b ESCAPE_BYTE n-1 b
     * The ESCAPE_BYTE value is chosen so as not to collide with commonly
     * seen values.
     */
    static final String arrayToRLEString(byte[] a) {
    StringBuffer buffer = new StringBuffer();
    buffer.append((char) (a.length >> 16));
    buffer.append((char) a.length);
    byte runValue = a[0];
    int runLength = 1;
    byte[] state = new byte[2];
    for (int i=1; i<a.length; ++i) {
        byte b = a[i];
        if (b == runValue && runLength < 0xFF) ++runLength;
        else {
        encodeRun(buffer, runValue, runLength, state);
        runValue = b;
        runLength = 1;
        }