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.asterix.runtime.evaluators.staticcodegen;
  
  import org.apache.asterix.om.types.ATypeTag;
  import org.apache.hyracks.data.std.api.IPointable;
  
  /**
   * The missing/null-handling code to be injected into the evaluator(...) method of scalar evaluators.
   */
  public class TypeChecker {
  
      private byte[] MISSING_BYTES = new byte[] { ATypeTag.SERIALIZED_MISSING_TYPE_TAG };
      private byte[] NULL_BYTES = new byte[] { ATypeTag.SERIALIZED_NULL_TYPE_TAG };
      private boolean meetNull = false;
  
      /**
       * This method should be called for each argument of a function.
       *
       * @param arg,
       *            the argument pointable.
       * @param resultPointable,
       *            the returned result for the function.
       * @return true if arg is MISSING; false otherwise.
       */
      public boolean isMissing(IPointable arg, IPointable resultPointable) {
          byte[] data = arg.getByteArray();
          int start = arg.getStartOffset();
          byte serializedTypeTag = data[start];
          if (serializedTypeTag == ATypeTag.SERIALIZED_MISSING_TYPE_TAG) {
              resultPointable.set(MISSING_BYTES, 0, 1);
              // resets meetNull for the next evaluate(...) call.
              meetNull = false;
              return true;
          }
          if (serializedTypeTag == ATypeTag.SERIALIZED_NULL_TYPE_TAG) {
              meetNull |= true;
          }
          return false;
      }
  
      /**
       * This method should be called after all arguments for a function are evaluated.
       *
       * @param resultPointable,
       *            the returned result for the function.
       * @return true if any argument is NULL; false otherwise.
       */
      public boolean isNull(IPointable resultPointable) {
          if (meetNull) {
              resultPointable.set(NULL_BYTES, 0, 1);
              // resets meetNull.
              meetNull = false;
              return true;
          }
          // resets meetNull for the next evaluate(...) call.
          meetNull = false;
          return false;
      }
  
  }
  