byteutils.java

非常棒的java数据库

/*
 * Copyright 2004-2008 H2 Group. Licensed under the H2 License, Version 1.0
 * (http://h2database.com/html/license.html).
 * Initial Developer: H2 Group
 */
package org.h2.util;

import java.sql.SQLException;

import org.h2.constant.ErrorCode;
import org.h2.message.Message;

/**
 * This utility class contains functions related to byte arrays.
 */
public class ByteUtils {

    private static final char[] HEX = "0123456789abcdef".toCharArray();

    public static int readInt(byte[] buff, int pos) {
        return (buff[pos++] << 24) + ((buff[pos++] & 0xff) << 16) + ((buff[pos++] & 0xff) << 8) + (buff[pos++] & 0xff);
    }

    public static long readLong(byte[] buff, int pos) {
        return ((long) (readInt(buff, pos)) << 32) + (readInt(buff, pos + 4) & 0xffffffffL);
    }

    public static int indexOf(byte[] bytes, byte[] pattern, int start) {
        if (pattern.length == 0) {
            return start;
        }
        if (start > bytes.length) {
            return -1;
        }
        int last = bytes.length - pattern.length + 1;
        next: for (; start < last; start++) {
            for (int i = 0; i < pattern.length; i++) {
                if (bytes[start + i] != pattern[i]) {
                    continue next;
                }
            }
            return start;
        }
        return -1;
    }

    public static byte[] convertStringToBytes(String s) throws SQLException {
        int len = s.length();
        if (len % 2 != 0) {
            throw Message.getSQLException(ErrorCode.HEX_STRING_ODD_1, s);
        }
        len /= 2;
        byte[] buff = new byte[len];
        for (int i = 0; i < len; i++) {
            buff[i] = (byte) ((getHexDigit(s, i + i) << 4) | getHexDigit(s, i + i + 1));
        }
        return buff;
    }

    private static int getHexDigit(String s, int i) throws SQLException {
        char c = s.charAt(i);
        if (c >= '0' && c <= '9') {
            return c - '0';
        } else if (c >= 'a' && c <= 'f') {
            return c - 'a' + 0xa;
        } else if (c >= 'A' && c <= 'F') {
            return c - 'A' + 0xa;
        } else {
            throw Message.getSQLException(ErrorCode.HEX_STRING_WRONG_1, s);
        }
    }

    public static int getByteArrayHash(byte[] value) {
        int h = 1;
        for (int i = 0; i < value.length;) {
            h = 31 * h + value[i++];
        }
        return h;
    }

    public static String convertBytesToString(byte[] value) {
        return convertBytesToString(value, value.length);
    }

    public static String convertBytesToString(byte[] value, int len) {
        char[] buff = new char[len + len];
        char[] hex = HEX;
        for (int i = 0; i < len; i++) {
            int c = value[i] & 0xff;
            buff[i + i] = hex[c >> 4];
            buff[i + i + 1] = hex[c & 0xf];
        }
        return new String(buff);
    }

    public static boolean compareSecure(byte[] test, byte[] good) {
        if ((test == null) || (good == null)) {
            return (test == null) && (good == null);
        }
        if (test.length != good.length) {
            return false;
        }
        if (test.length == 0) {
            return true;
        }
        // silly loop: this should help a little against timing attacks
        boolean correct = true, correct2 = false;
        for (int i = 0; i < good.length; i++) {
            if (test[i] != good[i]) {
                correct = false;
            } else {
                correct2 = true;
            }
        }
        return correct && correct2;
    }

    public static void clear(byte[] buff) {
        for (int i = 0; i < buff.length; i++) {
            buff[i] = 0;
        }
    }

    public static int compareNotNull(byte[] data1, byte[] data2) {
        int len = Math.min(data1.length, data2.length);
        for (int i = 0; i < len; i++) {
            byte b = data1[i];
            byte b2 = data2[i];
            if (b != b2) {
                return b > b2 ? 1 : -1;
            }
        }
        int c = data1.length - data2.length;
        return c == 0 ? 0 : (c < 0 ? -1 : 1);
    }

    public static String convertToBinString(byte[] buff) {
        char[] chars = new char[buff.length];
        for (int i = 0; i < buff.length; i++) {
            chars[i] = (char) (buff[i] & 0xff);
        }
        return new String(chars);
    }

    public static byte[] convertBinStringToBytes(String data) {
        byte[] buff = new byte[data.length()];
        for (int i = 0; i < data.length(); i++) {
            buff[i] = (byte) (data.charAt(i) & 0xff);
        }
        return buff;
    }

    public static byte[] copy(byte[] source, byte[] target) {
        int len = source.length;
        if (len > target.length) {
            target = new byte[len];
        }
        System.arraycopy(source, 0, target, 0, len);
        return target;
    }

    public static byte[] cloneByteArray(byte[] b) {
        int len = b.length;
        if (len == 0) {
            return b;
        }
        byte[] copy = new byte[len];
        System.arraycopy(b, 0, copy, 0, len);
        return copy;
    }

}