/*
    * Copyright 2012 The Netty Project
    *
    * The Netty Project 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:
    *
    *   https://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 io.netty.handler.codec.socks;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.util.CharsetUtil;
  import io.netty.util.internal.StringUtil;
  
  final class SocksCommonUtils {
      public static final SocksRequest UNKNOWN_SOCKS_REQUEST = new UnknownSocksRequest();
      public static final SocksResponse UNKNOWN_SOCKS_RESPONSE = new UnknownSocksResponse();
  
      /**
       * A constructor to stop this class being constructed.
       */
      private SocksCommonUtils() {
          // NOOP
      }
  
      private static final char ipv6hextetSeparator = ':';
  
      /**
       * Converts numeric IPv6 to standard (non-compressed) format.
       */
      public static String ipv6toStr(byte[] src) {
          assert src.length == 16;
          StringBuilder sb = new StringBuilder(39);
          ipv6toStr(sb, src, 0, 8);
          return sb.toString();
      }
  
      private static void ipv6toStr(StringBuilder sb, byte[] src, int fromHextet, int toHextet) {
          int i;
          toHextet --;
          for (i = fromHextet; i < toHextet; i++) {
              appendHextet(sb, src, i);
              sb.append(ipv6hextetSeparator);
          }
  
          appendHextet(sb, src, i);
      }
  
      private static void appendHextet(StringBuilder sb, byte[] src, int i) {
          StringUtil.toHexString(sb, src, i << 1, 2);
      }
  
      static String readUsAscii(ByteBuf buffer, int length) {
          String s = buffer.toString(buffer.readerIndex(), length, CharsetUtil.US_ASCII);
          buffer.skipBytes(length);
          return s;
      }
  }