content: /*
   * Licensed 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 io.airlift.bytecode.control;
  
  import com.google.common.collect.ImmutableList;
  import io.airlift.bytecode.BytecodeBlock;
  import io.airlift.bytecode.BytecodeNode;
  import io.airlift.bytecode.BytecodeVisitor;
  import io.airlift.bytecode.MethodGenerationContext;
  import io.airlift.bytecode.instruction.LabelNode;
  import org.objectweb.asm.MethodVisitor;
  
  import java.util.List;
  
  import static com.google.common.base.Preconditions.checkState;
  
  public class WhileLoop
          implements FlowControl
  {
      private final String comment;
      private final BytecodeBlock condition = new BytecodeBlock();
      private final BytecodeBlock body = new BytecodeBlock();
  
      private final LabelNode continueLabel = new LabelNode("continue");
      private final LabelNode endLabel = new LabelNode("end");
  
      public WhileLoop()
      {
          this.comment = null;
      }
  
      public WhileLoop(String format, Object... args)
      {
          this.comment = String.format(format, args);
      }
  
      @Override
      public String getComment()
      {
          return comment;
      }
  
      public LabelNode getContinueLabel()
      {
          return continueLabel;
      }
  
      public LabelNode getEndLabel()
      {
          return endLabel;
      }
  
      public BytecodeBlock condition()
      {
          return condition;
      }
  
      public WhileLoop condition(BytecodeNode node)
      {
          checkState(condition.isEmpty(), "condition already set");
          condition.append(node);
          return this;
      }
  
      public BytecodeBlock body()
      {
          return body;
      }
  
      public WhileLoop body(BytecodeNode node)
      {
          checkState(body.isEmpty(), "body already set");
          body.append(node);
          return this;
      }
  
      @Override
      public void accept(MethodVisitor visitor, MethodGenerationContext generationContext)
      {
          checkState(!condition.isEmpty(), "WhileLoop does not have a condition set");
  
          BytecodeBlock block = new BytecodeBlock()
                  .visitLabel(continueLabel)
                  .append(condition)
                  .ifZeroGoto(endLabel)
                  .append(body)
                  .gotoLabel(continueLabel)
                  .visitLabel(endLabel);
  
          block.accept(visitor, generationContext);
      }
  
      @Override
      public List<BytecodeNode> getChildNodes()
      {
          return ImmutableList.of(condition, body);
      }
  
      @Override
      public <T> T accept(BytecodeNode parent, BytecodeVisitor<T> visitor)
      {
          return visitor.visitWhile(parent, this);
      }
  }
  