bytearray.java

一个用java写的开源的数据库系统

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 * list of conditions and the following disclaimer, including earlier
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package org.hsqldb;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.sql.SQLException;

// fredt@users 20020320 - doc 1.7.0 - update
// fredt@users 20020825 - patch 1.7.1 - converted to static methods only
// BINARY objest are now represented internally as byte[] and use the static
// methods in this class to compare or convert the byte[] objects

/**
 *  This class allows HSQLDB to store binary data as an array of bytes. It
 *  contains methods to create and access the data, perform comparisons,
 *  etc.
 *
 * @version  1.7.0
 */
class ByteArray {

    /**
     * Private constructor, no instance of this is available.
     *
     */
    private ByteArray() {}

    /**
     * Converts the specified hexadecimal digit <CODE>String</CODE>
     * to an equivalent array of bytes.
     *
     * @param hexString a <CODE>String</CODE> of hexadecimal digits
     * @throws SQLException if the specified string contains non-hexadecimal digits.
     * @return a byte array equivalent to the specified string of hexadecimal digits
     */
    static byte[] hexToByteArray(String hexString) throws SQLException {
        return StringConverter.hexToByte(hexString);
    }

    /**
     * Compares a <CODE>byte[]</CODE> with another specified
     * <CODE>byte[]</CODE> for order.  Returns a negative integer, zero,
     * or a positive integer as the first object is less than, equal to, or
     * greater than the specified second <CODE>byte[]</CODE>.<p>
     *
     * @param o1 the first byte[] to be compared
     * @param o2 the second byte[] to be compared
     * @return a negative integer, zero, or a positive integer as this object
     * is less than, equal to, or greater than the specified object.
     */
    static int compareTo(byte[] o1, byte[] o2) {

        int len  = o1.length;
        int lenb = o2.length;

        for (int i = 0; ; i++) {
            int a = 0;
            int b = 0;

            if (i < len) {
                a = ((int) o1[i]) & 0xff;
            } else if (i >= lenb) {
                return 0;
            }

            if (i < lenb) {
                b = ((int) o2[i]) & 0xff;
            }

            if (a > b) {
                return 1;
            }

            if (b > a) {
                return -1;
            }
        }
    }

    /**
     * Retrieves the serialized form of the specified <CODE>Object</CODE>
     * as an array of bytes.
     *
     * @param s the Object to serialize
     * @return  a static byte array representing the passed Object
     * @throws SQLException if a serialization failure occurs
     */
    static byte[] serialize(Object s) throws SQLException {

        ByteArrayOutputStream bo = new ByteArrayOutputStream();

        try {
            ObjectOutputStream os = new ObjectOutputStream(bo);

            os.writeObject(s);

            return bo.toByteArray();
        } catch (Exception e) {
            throw Trace.error(Trace.SERIALIZATION_FAILURE, e.getMessage());
        }
    }

    /**
     * Retrieves the serialized form of the specified <CODE>Object</CODE>
     * as an equivalent <CODE>String</CODE> of hexadecimal digits.
     *
     * @param s the Object to serialize
     * @return  A String representing the passed Object
     * @throws SQLException if a serialization failure occurs
     */
    static String serializeToString(Object s) throws SQLException {
        return StringConverter.byteToHex(serialize(s));
    }

    /**
     * Deserializes the specified byte array to an
     * <CODE>Object</CODE> instance.
     *
     * @return the Object resulting from deserializing the specified array of bytes
     * @param ba the byte array to deserialize to an Object
     * @throws SQLException if a serialization failure occurs
     */
    static Object deserialize(byte[] ba) throws SQLException {

        try {
            ByteArrayInputStream bi = new ByteArrayInputStream(ba);
            ObjectInputStream    is = new ObjectInputStream(bi);

            return is.readObject();
        } catch (Exception e) {
            throw Trace.error(Trace.SERIALIZATION_FAILURE, e.getMessage());
        }
    }

    /**
     * Converts an array of bytes to an equivalent
     * <CODE>String</CODE> of hexadecimal digits.
     *
     * @return  String representation of the byte[].
     */
    static public String toString(byte[] o) {
        return StringConverter.byteToHex(o);
    }
}