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package net.dongliu.commons.codec;

/**
 * Utils method for hex
 *
 * @author Liu Dong
 */
public class Hexes {

    private static final char[] hexArray = "0123456789ABCDEF".toCharArray();
    private static final char[] hexArrayLower = "0123456789abcdef".toCharArray();

    /**
     * Convert bytes to hex string in upper case. Return null if bytes is null
     */
    public static String hexUpper(byte[] bytes) {
        char[] hexChars = new char[bytes.length * 2];
        for (int j = 0; j < bytes.length; j++) {
            int v = bytes[j] & 0xFF;
            hexChars[j * 2] = hexArray[v >>> 4];
            hexChars[j * 2 + 1] = hexArray[v & 0x0F];
        }
        return new String(hexChars);
    }

    /**
     * Convert bytes to hex string in lower case. Return null if bytes is null
     */
    public static String hexLower(byte[] bytes) {
        char[] hexChars = new char[bytes.length * 2];
        for (int j = 0; j < bytes.length; j++) {
            int v = bytes[j] & 0xFF;
            hexChars[j * 2] = hexArrayLower[v >>> 4];
            hexChars[j * 2 + 1] = hexArrayLower[v & 0x0F];
        }
        return new String(hexChars);
    }

    /**
     * Convert hex string back to bytes. Return null if str is null.
     */
    public static byte[] decode(CharSequence str) {
        int len = str.length();
        byte[] data = new byte[len / 2];
        for (int i = 0; i < len; i += 2) {
            data[i / 2] = (byte) ((Character.digit(str.charAt(i), 16) << 4)
                    + Character.digit(str.charAt(i + 1), 16));
        }
        return data;
    }
}