k-9/k9mail-library/src/main/java/com/fsck/k9/mail/filter/Hex.java

/*
 * Copyright 2001-2004 The Apache Software Foundation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.fsck.k9.mail.filter;

/**
 * This code was copied from the Apache Commons project.
 * The unnecessary parts have been left out.
 */
public class Hex {
    /**
     * Used building output as Hex
     */
    private static final char[] DIGITS = {
        '0', '1', '2', '3', '4', '5', '6', '7',
        '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'
    };

    /**
     * Converts an array of bytes into an array of characters representing the hexadecimal values of each byte in order.
     * The returned array will be double the length of the passed array, as it takes two characters to represent any
     * given byte.
     *
     * @param data
     *                  a byte[] to convert to Hex characters
     * @return A char[] containing lower-case hexadecimal characters
     */
    public static char[] encodeHex(byte[] data) {

        int l = data.length;

        char[] out = new char[l << 1];

        // two characters form the hex value.
        for (int i = 0, j = 0; i < l; i++) {
            out[j++] = DIGITS[(0xF0 & data[i]) >>> 4 ];
            out[j++] = DIGITS[ 0x0F & data[i] ];
        }

        return out;
    }

}