content: package com.alibaba.fastjson.util;
  
  import java.util.Arrays;
  
  /**
   * A very fast and memory efficient class to encode and decode to and from BASE64 in full accordance with RFC 2045.<br>
   * <br>
   * On Windows XP sp1 with 1.4.2_04 and later ;), this encoder and decoder is about 10 times faster on small arrays (10 -
   * 1000 bytes) and 2-3 times as fast on larger arrays (10000 - 1000000 bytes) compared to
   * <code>sun.misc.Encoder()/Decoder()</code>.<br>
   * <br>
   * On byte arrays the encoder is about 20% faster than Jakarta Commons Base64 Codec for encode and about 50% faster for
   * decoding large arrays. This implementation is about twice as fast on very small arrays (&lt 30 bytes). If
   * source/destination is a <code>String</code> this version is about three times as fast due to the fact that the
   * Commons Codec result has to be recoded to a <code>String</code> from <code>byte[]</code>, which is very expensive.<br>
   * <br>
   * This encode/decode algorithm doesn't create any temporary arrays as many other codecs do, it only allocates the
   * resulting array. This produces less garbage and it is possible to handle arrays twice as large as algorithms that
   * create a temporary array. (E.g. Jakarta Commons Codec). It is unknown whether Sun's
   * <code>sun.misc.Encoder()/Decoder()</code> produce temporary arrays but since performance is quite low it probably
   * does.<br>
   * <br>
   * The encoder produces the same output as the Sun one except that the Sun's encoder appends a trailing line separator
   * if the last character isn't a pad. Unclear why but it only adds to the length and is probably a side effect. Both are
   * in conformance with RFC 2045 though.<br>
   * Commons codec seem to always att a trailing line separator.<br>
   * <br>
   * <b>Note!</b> The encode/decode method pairs (types) come in three versions with the <b>exact</b> same algorithm and
   * thus a lot of code redundancy. This is to not create any temporary arrays for transcoding to/from different format
   * types. The methods not used can simply be commented out.<br>
   * <br>
   * There is also a "fast" version of all decode methods that works the same way as the normal ones, but har a few
   * demands on the decoded input. Normally though, these fast verions should be used if the source if the input is known
   * and it hasn't bee tampered with.<br>
   * <br>
   * If you find the code useful or you find a bug, please send me a note at base64 @ miginfocom . com. Licence (BSD):
   * ============== Copyright (c) 2004, Mikael Grev, MiG InfoCom AB. (base64 @ miginfocom . com) All rights reserved.
   * Redistribution and use in source and binary forms, with or without modification, are permitted provided that the
   * following conditions are met: Redistributions of source code must retain the above copyright notice, this list of
   * conditions and the following disclaimer. Redistributions in binary form must reproduce the above copyright notice,
   * this list of conditions and the following disclaimer in the documentation and/or other materials provided with the
   * distribution. Neither the name of the MiG InfoCom AB nor the names of its contributors may be used to endorse or
   * promote products derived from this software without specific prior written permission. THIS SOFTWARE IS PROVIDED BY
   * THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
   * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
   * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
   * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
   * TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   * POSSIBILITY OF SUCH DAMAGE.
   * 
   * @version 2.2
   * @author Mikael Grev Date: 2004-aug-02 Time: 11:31:11
   */
  
  public class Base64 {
  
      public static final char[] CA = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".toCharArray();
      public static final int[]  IA = new int[256];
      static {
          Arrays.fill(IA, -1);
          for (int i = 0, iS = CA.length; i < iS; i++)
              IA[CA[i]] = i;
          IA['='] = 0;
      }
  
      /**
       * Decodes a BASE64 encoded char array that is known to be resonably well formatted. The method is about twice as
       * fast as {@link #decode(char[])}. The preconditions are:<br>
       * + The array must have a line length of 76 chars OR no line separators at all (one line).<br>
       * + Line separator must be "\r\n", as specified in RFC 2045 + The array must not contain illegal characters within
       * the encoded string<br>
       * + The array CAN have illegal characters at the beginning and end, those will be dealt with appropriately.<br>
       * 
       * @param chars The source array. Length 0 will return an empty array. <code>null</code> will throw an exception.
       * @return The decoded array of bytes. May be of length 0.
       */
      public final static byte[] decodeFast(char[] chars, int offset, int charsLen) {
          // Check special case
          if (charsLen == 0) {
              return new byte[0];
          }
  
          int sIx = offset, eIx = offset + charsLen - 1; // Start and end index after trimming.
  
          // Trim illegal chars from start
          while (sIx < eIx && IA[chars[sIx]] < 0)
              sIx++;
  
          // Trim illegal chars from end
          while (eIx > 0 && IA[chars[eIx]] < 0)
              eIx--;
  
          // get the padding count (=) (0, 1 or 2)
          int pad = chars[eIx] == '=' ? (chars[eIx - 1] == '=' ? 2 : 1) : 0; // Count '=' at end.
          int cCnt = eIx - sIx + 1; // Content count including possible separators
          int sepCnt = charsLen > 76 ? (chars[76] == '\r' ? cCnt / 78 : 0) << 1 : 0;
  
          int len = ((cCnt - sepCnt) * 6 >> 3) - pad; // The number of decoded bytes
          byte[] bytes = new byte[len]; // Preallocate byte[] of exact length
  
          // Decode all but the last 0 - 2 bytes.
          int d = 0;
          for (int cc = 0, eLen = (len / 3) * 3; d < eLen;) {
              // Assemble three bytes into an int from four "valid" characters.
              int i = IA[chars[sIx++]] << 18 | IA[chars[sIx++]] << 12 | IA[chars[sIx++]] << 6 | IA[chars[sIx++]];
  
              // Add the bytes
              bytes[d++] = (byte) (i >> 16);
              bytes[d++] = (byte) (i >> 8);
              bytes[d++] = (byte) i;
  
              // If line separator, jump over it.
              if (sepCnt > 0 && ++cc == 19) {
                  sIx += 2;
                  cc = 0;
              }
          }
  
          if (d < len) {
              // Decode last 1-3 bytes (incl '=') into 1-3 bytes
              int i = 0;
              for (int j = 0; sIx <= eIx - pad; j++)
                  i |= IA[chars[sIx++]] << (18 - j * 6);
  
              for (int r = 16; d < len; r -= 8)
                  bytes[d++] = (byte) (i >> r);
          }
  
          return bytes;
      }
      
      public final static byte[] decodeFast(String chars, int offset, int charsLen) {
          // Check special case
          if (charsLen == 0) {
              return new byte[0];
          }
  
          int sIx = offset, eIx = offset + charsLen - 1; // Start and end index after trimming.
  
          // Trim illegal chars from start
          while (sIx < eIx && IA[chars.charAt(sIx)] < 0)
              sIx++;
  
          // Trim illegal chars from end
          while (eIx > 0 && IA[chars.charAt(eIx)] < 0)
              eIx--;
  
          // get the padding count (=) (0, 1 or 2)
          int pad = chars.charAt(eIx) == '=' ? (chars.charAt(eIx - 1) == '=' ? 2 : 1) : 0; // Count '=' at end.
          int cCnt = eIx - sIx + 1; // Content count including possible separators
          int sepCnt = charsLen > 76 ? (chars.charAt(76) == '\r' ? cCnt / 78 : 0) << 1 : 0;
  
          int len = ((cCnt - sepCnt) * 6 >> 3) - pad; // The number of decoded bytes
          byte[] bytes = new byte[len]; // Preallocate byte[] of exact length
  
          // Decode all but the last 0 - 2 bytes.
          int d = 0;
          for (int cc = 0, eLen = (len / 3) * 3; d < eLen;) {
              // Assemble three bytes into an int from four "valid" characters.
              int i = IA[chars.charAt(sIx++)] << 18 | IA[chars.charAt(sIx++)] << 12 | IA[chars.charAt(sIx++)] << 6 | IA[chars.charAt(sIx++)];
  
              // Add the bytes
              bytes[d++] = (byte) (i >> 16);
              bytes[d++] = (byte) (i >> 8);
              bytes[d++] = (byte) i;
  
              // If line separator, jump over it.
              if (sepCnt > 0 && ++cc == 19) {
                  sIx += 2;
                  cc = 0;
              }
          }
  
          if (d < len) {
              // Decode last 1-3 bytes (incl '=') into 1-3 bytes
              int i = 0;
              for (int j = 0; sIx <= eIx - pad; j++)
                  i |= IA[chars.charAt(sIx++)] << (18 - j * 6);
  
              for (int r = 16; d < len; r -= 8)
                  bytes[d++] = (byte) (i >> r);
          }
  
          return bytes;
      }
  
      /**
       * Decodes a BASE64 encoded string that is known to be resonably well formatted. The method is about twice as fast
       * as {@link #decode(String)}. The preconditions are:<br>
       * + The array must have a line length of 76 chars OR no line separators at all (one line).<br>
       * + Line separator must be "\r\n", as specified in RFC 2045 + The array must not contain illegal characters within
       * the encoded string<br>
       * + The array CAN have illegal characters at the beginning and end, those will be dealt with appropriately.<br>
       * 
       * @param s The source string. Length 0 will return an empty array. <code>null</code> will throw an exception.
       * @return The decoded array of bytes. May be of length 0.
       */
      public final static byte[] decodeFast(String s) {
          // Check special case
          int sLen = s.length();
          if (sLen == 0) return new byte[0];
  
          int sIx = 0, eIx = sLen - 1; // Start and end index after trimming.
  
          // Trim illegal chars from start
          while (sIx < eIx && IA[s.charAt(sIx) & 0xff] < 0)
              sIx++;
  
          // Trim illegal chars from end
          while (eIx > 0 && IA[s.charAt(eIx) & 0xff] < 0)
              eIx--;
  
          // get the padding count (=) (0, 1 or 2)
          int pad = s.charAt(eIx) == '=' ? (s.charAt(eIx - 1) == '=' ? 2 : 1) : 0; // Count '=' at end.
          int cCnt = eIx - sIx + 1; // Content count including possible separators
          int sepCnt = sLen > 76 ? (s.charAt(76) == '\r' ? cCnt / 78 : 0) << 1 : 0;
  
          int len = ((cCnt - sepCnt) * 6 >> 3) - pad; // The number of decoded bytes
          byte[] dArr = new byte[len]; // Preallocate byte[] of exact length
  
          // Decode all but the last 0 - 2 bytes.
          int d = 0;
          for (int cc = 0, eLen = (len / 3) * 3; d < eLen;) {
              // Assemble three bytes into an int from four "valid" characters.
              int i = IA[s.charAt(sIx++)] << 18 | IA[s.charAt(sIx++)] << 12 | IA[s.charAt(sIx++)] << 6
                      | IA[s.charAt(sIx++)];
  
              // Add the bytes
              dArr[d++] = (byte) (i >> 16);
              dArr[d++] = (byte) (i >> 8);
              dArr[d++] = (byte) i;
  
              // If line separator, jump over it.
              if (sepCnt > 0 && ++cc == 19) {
                  sIx += 2;
                  cc = 0;
              }
          }
  
          if (d < len) {
              // Decode last 1-3 bytes (incl '=') into 1-3 bytes
              int i = 0;
              for (int j = 0; sIx <= eIx - pad; j++)
                  i |= IA[s.charAt(sIx++)] << (18 - j * 6);
  
              for (int r = 16; d < len; r -= 8)
                  dArr[d++] = (byte) (i >> r);
          }
  
          return dArr;
      }
  }
  