content: package org.aion.precompiled.util;
  
  import java.io.IOException;
  import java.io.OutputStream;
  
  /** A streaming Hex encoder. */
  public class HexEncoder {
  
      private static final byte[] encodingTable = {
          (byte) '0', (byte) '1', (byte) '2', (byte) '3', (byte) '4', (byte) '5', (byte) '6',
                  (byte) '7',
          (byte) '8', (byte) '9', (byte) 'a', (byte) 'b', (byte) 'c', (byte) 'd', (byte) 'e',
                  (byte) 'f'
      };
  
      /*
       * set up the decoding table.
       */
      private static final byte[] decodingTable = new byte[128];
  
      private void initialiseDecodingTable() {
          for (int i = 0; i < decodingTable.length; i++) {
              decodingTable[i] = (byte) 0xff;
          }
  
          for (int i = 0; i < encodingTable.length; i++) {
              decodingTable[encodingTable[i]] = (byte) i;
          }
  
          decodingTable['A'] = decodingTable['a'];
          decodingTable['B'] = decodingTable['b'];
          decodingTable['C'] = decodingTable['c'];
          decodingTable['D'] = decodingTable['d'];
          decodingTable['E'] = decodingTable['e'];
          decodingTable['F'] = decodingTable['f'];
      }
  
      public HexEncoder() {
          initialiseDecodingTable();
      }
  
      /**
       * encode the input data producing a Hex output stream.
       *
       * @return the number of bytes produced.
       */
      public static int encode(byte[] data, int off, int length, OutputStream out) {
          for (int i = off; i < (off + length); i++) {
              int v = data[i] & 0xff;
              try {
                  out.write(encodingTable[(v >>> 4)]);
                  out.write(encodingTable[v & 0xf]);
              } catch (Exception ignored) {
              }
          }
  
          return length * 2;
      }
  
      private static boolean ignore(char c) {
          return c == '\n' || c == '\r' || c == '\t' || c == ' ';
      }
  
      /**
       * decode the Hex encoded byte data writing it to the given output stream, whitespace characters
       * will be ignored.
       *
       * @return the number of bytes produced.
       */
      public static int decode(byte[] data, int off, int length, OutputStream out)
              throws IOException {
          byte b1, b2;
          int outLen = 0;
  
          int end = off + length;
  
          while (end > off) {
              if (!ignore((char) data[end - 1])) {
                  break;
              }
  
              --end;
          }
  
          int i = off;
          while (i < end) {
              while (i < end && ignore((char) data[i])) {
                  i++;
              }
  
              b1 = decodingTable[data[i++]];
  
              while (i < end && ignore((char) data[i])) {
                  i++;
              }
  
              b2 = decodingTable[data[i++]];
  
              if ((b1 | b2) < 0) {
                  throw new IOException("invalid characters encountered in Hex data");
              }
  
              try {
                  out.write((b1 << 4) | b2);
              } catch (Exception ignored) {
  
              }
  
              ++outLen;
          }
  
          return outLen;
      }
  
      /**
       * decode the Hex encoded String data writing it to the given output stream, whitespace
       * characters will be ignored.
       *
       * @return the number of bytes produced.
       */
      public static int decode(String data, OutputStream out) throws IOException {
          byte b1, b2;
          int length = 0;
  
          int end = data.length();
  
          while (end > 0) {
              if (!ignore(data.charAt(end - 1))) {
                  break;
              }
  
              --end;
          }
  
          int i = 0;
          while (i < end) {
              while (i < end && ignore(data.charAt(i))) {
                  ++i;
              }
  
              b1 = decodingTable[data.charAt(i++)];
  
              while (i < end && ignore(data.charAt(i))) {
                  ++i;
              }
  
              b2 = decodingTable[data.charAt(i++)];
  
              if ((b1 | b2) < 0) {
                  throw new IOException("invalid characters encountered in Hex string");
              }
  
              out.write((b1 << 4) | b2);
  
              ++length;
          }
  
          return length;
      }
  }
  