base64.java

SMS短信编程,该软件实现短信发送和接收的测试

package cmcctest;

/**
 * <p>Title: </p>
 * <p>Description: </p>
 * <p>Copyright: Copyright (c) 2003</p>
 * <p>Company: bbmf</p>
 * @author bihongbin
 * @version 1.0
 */

import sun.io.CharacterEncoding;

public class Base64
{
  /**
   * Base64字符集列表
   */
  private static char charKeySet[] = {
      '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', '+', '/'
  };

  //ASCII字符集对应的charKeySet的映射
  private static byte valueKeySet[] = {
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -1, -1, -1, 62, -1, -1, -1, 63, 52, 53,
      54, 55, 56, 57, 58, 59, 60, 61, -1, -1,
      -1, 0, -1, -1, -1, 0, 1, 2, 3, 4,
      5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
      15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
      25, -1, -1, -1, -1, -1, -1, 26, 27, 28,
      29, 30, 31, 32, 33, 34, 35, 36, 37, 38,
      39, 40, 41, 42, 43, 44, 45, 46, 47, 48,
      49, 50, 51, -1, -1, -1, -1, -1
  };

  private Base64() {
  }

  /**
   * 编码函数，即对参数b[]按照Base64进行编码
   * @param b 待编码的字节数组
   * @return 返回按照Base64编码后的字符串
   * @since SMS1.0
   */
  public static String encode(byte b[]) {
    int code = 0;
    int size = 0;
    //首先确定编码后的字符长度
    if (b.length % 3 == 0)
      size = (b.length / 3) * 4;
    else
      size = (b.length / 3 + 1) * 4;

    //根据b[]的长度，确定经过BASE64编码转换后的字符长度size,并申请一个size长度的sb，存放编码后的字符
    StringBuffer sb = new StringBuffer(size);
    for (int i = 0; i < b.length; i++) { //先把每3个字节组合起来形成24位的二进制序列，然后每6位分开，分成4个字节。
      if (i % 3 == 0)
        code |= b[i] << 16;
      else if (i % 3 == 1)
        code |= b[i] << 8;
      else
        code |= b[i];
      if (i % 3 == 2 || i == b.length - 1) {
        sb.append(charKeySet[ (code & 0xfc0000) >>> 18]); //0xfc0000即把后18位变成0，然后右移18位得第一个字符
        sb.append(charKeySet[ (code & 0x3f000) >>> 12]); //对18位到12位取全1的与应算后向右移动12位得到第2个字符
        sb.append(charKeySet[ (code & 0xfc0) >>> 6]); //对12位到6位取全1的与应算后向右移动6位得到第3个字符
        sb.append(charKeySet[code & 0x3f]); //对最后6位取全1并与得到最后一个字符。
        code = 0;
      }
    }

    if (b.length % 3 > 0)
      sb.setCharAt(sb.length() - 1, '=');
    if (b.length % 3 == 1)
      sb.setCharAt(sb.length() - 2, '=');
    return sb.toString();
  }

  /**
   * 解码函数，即对参数code按照Base64进行解码，并返回解码后字节数组
   * @param code 待解码的字符串
   * @return 返回按照Base64解码后的字节码
   * @since SMS1.0
   */
  public static byte[] decode(String code) {
    if (code == null)
      return null;
    int len = code.length();
    if (len % 4 != 0)
      throw new IllegalArgumentException("Base64 string length must be 4*n");
    if (code.length() == 0)
      return new byte[0];
    int pad = 0;
    if (code.charAt(len - 1) == '=')
      pad++;
    if (code.charAt(len - 2) == '=')
      pad++;
    int retLen = (len / 4) * 3 - pad; //去掉“==”得出原字符的长度。
    byte ret[] = new byte[retLen];
    for (int i = 0; i < len; i += 4) {
      int j = (i / 4) * 3;
      char ch1 = code.charAt(i);
      char ch2 = code.charAt(i + 1);
      char ch3 = code.charAt(i + 2);
      char ch4 = code.charAt(i + 3);
      int tmp = valueKeySet[ch1] << 18 | valueKeySet[ch2] << 12 |
          valueKeySet[ch3] << 6 | valueKeySet[ch4];
      ret[j] = (byte) ( (tmp & 0xff0000) >> 16);
      if (i < len - 4) {
        ret[j + 1] = (byte) ( (tmp & 0xff00) >> 8);
        ret[j + 2] = (byte) (tmp & 0xff);
      }
      else {
        if (j + 1 < retLen)
          ret[j + 1] = (byte) ( (tmp & 0xff00) >> 8);
        if (j + 2 < retLen)
          ret[j + 2] = (byte) (tmp & 0xff);
      }
    }

    return ret;
  }

// for test
  public static void main(String[] args) {
    String str = "admin112";
    String estr = Base64.encode(str.getBytes());
    System.out.println(estr);
    StringBuffer buff = new StringBuffer(new String(Base64.decode(estr)));
    System.out.println(buff.toString());
  }
}