content: /*
   * Copyright (C) 2020 ActiveJ LLC.
   *
   * 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.activej.codegen.expression.impl;
  
  import io.activej.codegen.Context;
  import io.activej.codegen.expression.Expression;
  import io.activej.common.annotation.ExposedInternals;
  import org.objectweb.asm.Label;
  import org.objectweb.asm.Type;
  import org.objectweb.asm.commons.GeneratorAdapter;
  
  import static io.activej.codegen.util.TypeChecks.checkType;
  import static io.activej.codegen.util.TypeChecks.isAssignable;
  import static io.activej.codegen.util.Utils.isPrimitiveType;
  
  @ExposedInternals
  public final class IfNull implements Expression {
  	public final Expression expression;
  	public final Expression expressionTrue;
  	public final Expression expressionFalse;
  
  	public IfNull(Expression expression, Expression expressionTrue, Expression expressionFalse) {
  		this.expression = expression;
  		this.expressionTrue = expressionTrue;
  		this.expressionFalse = expressionFalse;
  	}
  
  	@Override
  	public Type load(Context ctx) {
  		GeneratorAdapter g = ctx.getGeneratorAdapter();
  
  		Label labelTrue = new Label();
  		Label labelExit = new Label();
  
  		Type argType = expression.load(ctx);
  		checkType(argType, isAssignable());
  
  		if (isPrimitiveType(argType)) {
  			if (argType.getSize() == 1)
  				g.pop();
  			if (argType.getSize() == 2)
  				g.pop2();
  			return expressionFalse.load(ctx);
  		}
  
  		g.ifNull(labelTrue);
  
  		Type typeFalse = expressionFalse.load(ctx);
  		g.goTo(labelExit);
  
  		g.mark(labelTrue);
  		Type typeTrue = expressionTrue.load(ctx);
  
  		g.mark(labelExit);
  
  		return ctx.unifyTypes(typeFalse, typeTrue);
  	}
  }
  