Base64.java

/*
 * Copyright 2001-2006 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.
 */

/*
 * Copyright 2008-2009 MOPAS(Ministry of Public Administration and Security).
 *
 * 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 egovframework.rte.fdl.idgnr.impl;

/**
 * Base64 Encoding 클래스
 * @author 실행환경 개발팀 김태호
 * @since 2009.02.01
 * @version 1.0
 * @see <pre>
 *  == 개정이력(Modification Information) ==
 *   
 *   수정일      수정자           수정내용
 *  -------    --------    ---------------------------
 *   2009.02.01  김태호          최초 생성
 * 
 * </pre>
 */
public class Base64 {
    /**
     * 기본 생성자
     */
    private Base64() {

    }

    /*
     * Base Char 정의
     */
    private static final char[] S_BASE64CHAR =
        {'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N',
            'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a',
            'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
            'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0',
            '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/' };

    private static final char S_BASE64PAD = '=';

    private static final byte[] S_DECODETABLE = new byte[128];
    static {
        for (int i = 0; i < S_DECODETABLE.length; i++)
            S_DECODETABLE[i] = Byte.MAX_VALUE; // 127
        for (int i = 0; i < S_BASE64CHAR.length; i++)
            // 0 to 63
            S_DECODETABLE[S_BASE64CHAR[i]] = (byte) i;
    }

    /**
     * byte 타입의 데이터를 입력받아 String 타입으로 인코딩하여 리턴
     * @param data
     *        base64 data to be encoded
     * @return outstream to be returned a encoded data
     */
    public static String encode(byte[] data) {
        return encode(data, 0, data.length);
    }

    /**
     * 인코딩대상 byte정보와 시작점 길이를 입력받아서 String 타입으로 인코딩하여 리턴
     * @param data
     *        base64 data to be encoded
     * @param off
     *        data offset
     * @param len
     *        data length
     * @return encoded data
     */
    public static String encode(byte[] data, int off, int len) {
        if (len <= 0)
            return "";
        char[] out = new char[len / 3 * 4 + 4];
        int rindex = off;
        int windex = 0;
        int rest = len;
        while (rest >= 3) {
            int i =
                ((data[rindex] & 0xff) << 16)
                    + ((data[rindex + 1] & 0xff) << 8)
                    + (data[rindex + 2] & 0xff);
            out[windex++] = S_BASE64CHAR[i >> 18];
            out[windex++] = S_BASE64CHAR[(i >> 12) & 0x3f];
            out[windex++] = S_BASE64CHAR[(i >> 6) & 0x3f];
            out[windex++] = S_BASE64CHAR[i & 0x3f];
            rindex += 3;
            rest -= 3;
        }
        if (rest == 1) {
            int i = data[rindex] & 0xff;
            out[windex++] = S_BASE64CHAR[i >> 2];
            out[windex++] = S_BASE64CHAR[(i << 4) & 0x3f];
            out[windex++] = S_BASE64PAD;
            out[windex++] = S_BASE64PAD;
        } else if (rest == 2) {
            int i = ((data[rindex] & 0xff) << 8) + (data[rindex + 1] & 0xff);
            out[windex++] = S_BASE64CHAR[i >> 10];
            out[windex++] = S_BASE64CHAR[(i >> 4) & 0x3f];
            out[windex++] = S_BASE64CHAR[(i << 2) & 0x3f];
            out[windex++] = S_BASE64PAD;
        }
        return new String(out, 0, windex);
    }
}