content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF 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.
   */
  
  package org.apache.guacamole.protocol;
  
  import org.apache.guacamole.GuacamoleException;
  import org.apache.guacamole.GuacamoleServerException;
  import org.apache.guacamole.io.GuacamoleWriter;
  
  /**
   * GuacamoleWriter which applies a given GuacamoleFilter to observe or alter
   * all written instructions. Instructions may also be dropped or denied by
   * the filter.
   *
   * @author Michael Jumper
   */
  public class FilteredGuacamoleWriter implements GuacamoleWriter {
  
      /**
       * The wrapped GuacamoleWriter.
       */
      private final GuacamoleWriter writer;
  
      /**
       * The filter to apply when writing instructions.
       */
      private final GuacamoleFilter filter;
  
      /**
       * Parser for reading instructions prior to writing, such that they can be
       * passed on to the filter.
       */
      private final GuacamoleParser parser = new GuacamoleParser();
      
      /**
       * Wraps the given GuacamoleWriter, applying the given filter to all written 
       * instructions. Future writes will only write instructions which pass
       * the filter.
       *
       * @param writer The GuacamoleWriter to wrap.
       * @param filter The filter which dictates which instructions are written,
       *               and how.
       */
      public FilteredGuacamoleWriter(GuacamoleWriter writer, GuacamoleFilter filter) {
          this.writer = writer;
          this.filter = filter;
      }
   
      @Override
      public void write(char[] chunk, int offset, int length) throws GuacamoleException {
  
          // Write all data in chunk
          while (length > 0) {
  
              // Pass as much data through the parser as possible
              int parsed;
              while ((parsed = parser.append(chunk, offset, length)) != 0) {
                  offset += parsed;
                  length -= parsed;
              }
  
              // If no instruction is available, it must be incomplete
              if (!parser.hasNext())
                  throw new GuacamoleServerException("Filtered write() contained an incomplete instruction.");
  
              // Write single instruction through filter
              writeInstruction(parser.next());
  
          }
          
      }
  
      @Override
      public void write(char[] chunk) throws GuacamoleException {
          write(chunk, 0, chunk.length);
      }
  
      @Override
      public void writeInstruction(GuacamoleInstruction instruction) throws GuacamoleException {
  
          // Write instruction only if not dropped
          GuacamoleInstruction filteredInstruction = filter.filter(instruction);
          if (filteredInstruction != null)
              writer.writeInstruction(filteredInstruction);
  
      }
  
  }
  