/*
    * 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:
    *
    *   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.
   */
  /*
   * Adaptation of http://bjoern.hoehrmann.de/utf-8/decoder/dfa/
   *
   * Copyright (c) 2008-2009 Bjoern Hoehrmann <[email protected]>
   *
   * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
   * and associated documentation files (the "Software"), to deal in the Software without restriction,
   * including without limitation the rights to use, copy, modify, merge, publish, distribute,
   * sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
   * furnished to do so, subject to the following conditions:
   *
   * The above copyright notice and this permission notice shall be included in all copies or
   * substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING
   * BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
   * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
   * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
   */
  package io.netty.handler.codec.http.websocketx;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.buffer.ByteBufProcessor;
  import io.netty.handler.codec.CorruptedFrameException;
  
  /**
   * Checks UTF8 bytes for validity
   */
  final class Utf8Validator implements ByteBufProcessor {
      private static final int UTF8_ACCEPT = 0;
      private static final int UTF8_REJECT = 12;
  
      private static final byte[] TYPES = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
              0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
              0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
              0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
              0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1,
              1, 1, 1, 1, 1, 1, 1, 1, 1, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 7, 7, 7, 7,
              7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 8,
              8, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
              2, 2, 10, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 3, 3, 11, 6, 6, 6, 5, 8, 8, 8, 8, 8,
              8, 8, 8, 8, 8, 8 };
  
      private static final byte[] STATES = { 0, 12, 24, 36, 60, 96, 84, 12, 12, 12, 48, 72, 12, 12,
              12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 0, 12, 12, 12, 12, 12, 0, 12, 0, 12, 12,
              12, 24, 12, 12, 12, 12, 12, 24, 12, 24, 12, 12, 12, 12, 12, 12, 12, 12, 12, 24, 12, 12,
              12, 12, 12, 24, 12, 12, 12, 12, 12, 12, 12, 24, 12, 12, 12, 12, 12, 12, 12, 12, 12, 36,
              12, 36, 12, 12, 12, 36, 12, 12, 12, 12, 12, 36, 12, 36, 12, 12, 12, 36, 12, 12, 12, 12,
              12, 12, 12, 12, 12, 12 };
  
      @SuppressWarnings("RedundantFieldInitialization")
      private int state = UTF8_ACCEPT;
      private int codep;
      private boolean checking;
  
      public void check(ByteBuf buffer) {
          checking = true;
          buffer.forEachByte(this);
      }
  
      public void finish() {
          checking = false;
          codep = 0;
          if (state != UTF8_ACCEPT) {
              state = UTF8_ACCEPT;
              throw new CorruptedFrameException("bytes are not UTF-8");
          }
      }
  
      @Override
      public boolean process(byte b) throws Exception {
          byte type = TYPES[b & 0xFF];
  
          codep = state != UTF8_ACCEPT ? b & 0x3f | codep << 6 : 0xff >> type & b;
  
          state = STATES[state + type];
  
          if (state == UTF8_REJECT) {
              checking = false;
              throw new CorruptedFrameException("bytes are not UTF-8");
          }
          return true;
      }
 
     public boolean isChecking() {
         return checking;
     }
 }