content: /**
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You 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 org.apache.solr.common.util;
  
  /**
   * Static methods for translating Base64 encoded strings to byte arrays
   * and vice-versa. 
   */
  
  public class Base64 {
    /**
     * This array is a lookup table that translates 6-bit positive integer
     * index values into their "Base64 Alphabet" equivalents as specified
     * in Table 1 of RFC 2045.
     */
    private static final char intToBase64[] = {
            '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', '+', '/'
    };
  
    /**
     * This array is a lookup table that translates unicode characters
     * drawn from the "Base64 Alphabet" (as specified in Table 1 of RFC 2045)
     * into their 6-bit positive integer equivalents.  Characters that
     * are not in the Base64 alphabet but fall within the bounds of the
     * array are translated to -1.
     */
    private static final byte base64ToInt[] = {
            -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, -1, -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
    };
  
    public static String byteArrayToBase64(byte[] a, int offset, int len) {
      int aLen = len;
      int numFullGroups = aLen / 3;
      int numBytesInPartialGroup = aLen - 3 * numFullGroups;
      int resultLen = 4 * ((aLen + 2) / 3);
      StringBuffer result = new StringBuffer(resultLen);
      char[] intToAlpha = intToBase64;
  
      // Translate all full groups from byte array elements to Base64
      int inCursor = offset;
      for (int i = 0; i < numFullGroups; i++) {
        int byte0 = a[inCursor++] & 0xff;
        int byte1 = a[inCursor++] & 0xff;
        int byte2 = a[inCursor++] & 0xff;
        result.append(intToAlpha[byte0 >> 2]);
        result.append(intToAlpha[(byte0 << 4) & 0x3f | (byte1 >> 4)]);
        result.append(intToAlpha[(byte1 << 2) & 0x3f | (byte2 >> 6)]);
        result.append(intToAlpha[byte2 & 0x3f]);
      }
  
      // Translate partial group if present
      if (numBytesInPartialGroup != 0) {
        int byte0 = a[inCursor++] & 0xff;
        result.append(intToAlpha[byte0 >> 2]);
        if (numBytesInPartialGroup == 1) {
          result.append(intToAlpha[(byte0 << 4) & 0x3f]);
          result.append("==");
        } else {
          // assert numBytesInPartialGroup == 2;
          int byte1 = a[inCursor++] & 0xff;
          result.append(intToAlpha[(byte0 << 4) & 0x3f | (byte1 >> 4)]);
          result.append(intToAlpha[(byte1 << 2) & 0x3f]);
          result.append('=');
        }
      }
      return result.toString();
    }
  
    public static byte[] base64ToByteArray(String s) {
      byte[] alphaToInt = base64ToInt;
      int sLen = s.length();
      int numGroups = sLen / 4;
      if (4 * numGroups != sLen)
        throw new IllegalArgumentException(
                "String length must be a multiple of four.");
      int missingBytesInLastGroup = 0;
      int numFullGroups = numGroups;
      if (sLen != 0) {
        if (s.charAt(sLen - 1) == '=') {
          missingBytesInLastGroup++;
          numFullGroups--;
        }
        if (s.charAt(sLen - 2) == '=')
          missingBytesInLastGroup++;
      }
      byte[] result = new byte[3 * numGroups - missingBytesInLastGroup];
  
      // Translate all full groups from base64 to byte array elements
      int inCursor = 0, outCursor = 0;
      for (int i = 0; i < numFullGroups; i++) {
        int ch0 = base64toInt(s.charAt(inCursor++), alphaToInt);
        int ch1 = base64toInt(s.charAt(inCursor++), alphaToInt);
        int ch2 = base64toInt(s.charAt(inCursor++), alphaToInt);
        int ch3 = base64toInt(s.charAt(inCursor++), alphaToInt);
        result[outCursor++] = (byte) ((ch0 << 2) | (ch1 >> 4));
        result[outCursor++] = (byte) ((ch1 << 4) | (ch2 >> 2));
        result[outCursor++] = (byte) ((ch2 << 6) | ch3);
      }
  
      // Translate partial group, if present
      if (missingBytesInLastGroup != 0) {
        int ch0 = base64toInt(s.charAt(inCursor++), alphaToInt);
        int ch1 = base64toInt(s.charAt(inCursor++), alphaToInt);
        result[outCursor++] = (byte) ((ch0 << 2) | (ch1 >> 4));
  
        if (missingBytesInLastGroup == 1) {
          int ch2 = base64toInt(s.charAt(inCursor++), alphaToInt);
          result[outCursor++] = (byte) ((ch1 << 4) | (ch2 >> 2));
        }
      }
      // assert inCursor == s.length()-missingBytesInLastGroup;
      // assert outCursor == result.length;
      return result;
    }
  
    /**
     * Translates the specified character, which is assumed to be in the
     * "Base 64 Alphabet" into its equivalent 6-bit positive integer.
     *
     * @throw IllegalArgumentException or ArrayOutOfBoundsException if
     * c is not in the Base64 Alphabet.
     */
    private static int base64toInt(char c, byte[] alphaToInt) {
      int result = alphaToInt[c];
      if (result < 0)
        throw new IllegalArgumentException("Illegal character " + c);
      return result;
    }
  }
  