content: package com.alibaba.fastjson.util;
  
  import java.util.Arrays;
  
  /**
   * @author Mikael Grev Date: 2004-aug-02 Time: 11:31:11
   * @version 2.2
   * @deprecated internal api, don't use.
   */
  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, j = CA.length; i < j; 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 #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 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 + 1]] << 12
                      | IA[chars[sIx + 2]] << 6
                      | IA[chars[sIx + 3]];
              sIx += 4;
  
              // Add the bytes
              bytes[d] = (byte) (i >> 16);
              bytes[d + 1] = (byte) (i >> 8);
              bytes[d + 2] = (byte) i;
              d += 3;
  
              // 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 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 + 1)] << 12
                      | IA[chars.charAt(sIx + 2)] << 6
                      | IA[chars.charAt(sIx + 3)];
              sIx += 4;
  
              // Add the bytes
              bytes[d] = (byte) (i >> 16);
              bytes[d + 1] = (byte) (i >> 8);
              bytes[d + 2] = (byte) i;
              d += 3;
  
              // 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 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 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 + 1)] << 12
                      | IA[s.charAt(sIx + 2)] << 6
                      | IA[s.charAt(sIx + 3)];
              sIx += 4;
  
              // Add the bytes
              dArr[d] = (byte) (i >> 16);
              dArr[d + 1] = (byte) (i >> 8);
              dArr[d + 2] = (byte) i;
              d += 3;
  
              // 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;
      }
  }
  