base64.java

用jbuilder写的源程序

/**
 * Copyright 2003-2006 the original author or authors.
 * 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.jdon.bussinessproxy.remote.http.util;

public class Base64 {

   protected static char getChar(int sixbit) {
      if (sixbit >= 0 && sixbit <= 25) {
         return (char)(65 + sixbit);
      }

      if (sixbit >= 26 && sixbit <= 51) {
         return (char)(97 + (sixbit - 26));
      }

      if (sixbit >= 52 && sixbit <= 61) {
         return (char)(48 + (sixbit - 52));
      }

      if (sixbit == 62) {
         return '+';
      }

      return sixbit != 63 ? '?' : '/';
   }

   protected static int getValue(char c) {
      if (c >= 'A' && c <= 'Z') {
         return c - 65;
      }

      if (c >= 'a' && c <= 'z') {
         return (c - 97) + 26;
      }

      if (c >= '0' && c <= '9') {
         return (c - 48) + 52;
      }

      if (c == '+') {
         return 62;
      }

      if (c == '/') {
         return 63;
      }

      return c != '=' ? -1 : 0;
   }

   public static String encode(byte raw[]) {
      StringBuffer encoded = new StringBuffer();

      for (int i = 0; i < raw.length; i += 3) {
         encoded.append(encodeBlock(raw, i));
      }

      return encoded.toString();
   }

   protected static char[] encodeBlock(byte raw[], int offset) {
      int block = 0;
      int slack = raw.length - offset - 1;
      int end = slack < 2 ? slack : 2;

      for (int i = 0; i <= end; i++) {
         byte b = raw[offset + i];

         int neuter = b >= 0 ? ((int) (b)) : b + 256;
         block += neuter << 8 * (2 - i);
      }

      char base64[] = new char[4];

      for (int i = 0; i < 4; i++) {
         int sixbit = block >>> 6 * (3 - i) & 0x3f;
         base64[i] = getChar(sixbit);
      }

      if (slack < 1) {
         base64[2] = '=';
      }

      if (slack < 2) {
         base64[3] = '=';
      }

      return base64;
   }

   public static byte[] decode(String base64) {
      int pad = 0;

      for (int i = base64.length() - 1; base64.charAt(i) == '='; i--) {
         pad++;
      }

      int length = (base64.length() * 6) / 8 - pad;
      byte raw[] = new byte[length];
      int rawindex = 0;

      for (int i = 0; i < base64.length(); i += 4) {
         int block = (getValue(base64.charAt(i)) << 18) +
                  (getValue(base64.charAt(i + 1)) << 12) +
                  (getValue(base64.charAt(i + 2)) << 6) +
                  getValue(base64.charAt(i + 3));

         for (int j = 0; j < 3 && rawindex + j < raw.length; j++) {
            raw[rawindex + j] = (byte)(block >> 8 * (2 - j) & 0xff);
         }

         rawindex += 3;
      }

      return raw;
   }

}