content: /*******************************************************************************
   * Copyright (c) 2009, 2019 Mountainminds GmbH & Co. KG and Contributors
   * All rights reserved. This program and the accompanying materials
   * are made available under the terms of the Eclipse Public License v1.0
   * which accompanies this distribution, and is available at
   * http://www.eclipse.org/legal/epl-v10.html
   *
   * Contributors:
   *    Marc R. Hoffmann - initial API and implementation
   *    
   *******************************************************************************/
  
  package org.jacoco.core.internal.flow;
  
  import java.util.ArrayList;
  import java.util.List;
  
  import org.objectweb.asm.MethodVisitor;
  import org.objectweb.asm.Opcodes;
  import org.objectweb.asm.commons.AnalyzerAdapter;
  
  /**
   * IFrame implementation which creates snapshots from an {@link AnalyzerAdapter}
   */
  class FrameSnapshot implements IFrame {
  
  	private static final FrameSnapshot NOP = new FrameSnapshot(null, null);
  
  	private final Object[] locals;
  	private final Object[] stack;
  
  	private FrameSnapshot(final Object[] locals, final Object[] stack) {
  		this.locals = locals;
  		this.stack = stack;
  	}
  
  	/**
  	 * Create a IFrame instance based on the given analyzer.
  	 * 
  	 * @param analyzer
  	 *            analyzer instance or <code>null</code>
  	 * @param popCount
  	 *            number of items to remove from the operand stack
  	 * @return IFrame instance. In case the analyzer is <code>null</code> or
  	 *         does not contain stackmap information a "NOP" IFrame is returned.
  	 */
  	static IFrame create(final AnalyzerAdapter analyzer, final int popCount) {
  		if (analyzer == null || analyzer.locals == null) {
  			return NOP;
  		}
  		final Object[] locals = reduce(analyzer.locals, 0);
  		final Object[] stack = reduce(analyzer.stack, popCount);
  		return new FrameSnapshot(locals, stack);
  	}
  
  	/**
  	 * Reduce double word types into a single slot as required
  	 * {@link MethodVisitor#visitFrame(int, int, Object[], int, Object[])}
  	 * method.
  	 */
  	private static Object[] reduce(final List<Object> source, final int popCount) {
  		final List<Object> copy = new ArrayList<Object>(source);
  		final int size = source.size() - popCount;
  		copy.subList(size, source.size()).clear();
  		for (int i = size; --i >= 0;) {
  			final Object type = source.get(i);
  			if (type == Opcodes.LONG || type == Opcodes.DOUBLE) {
  				copy.remove(i + 1);
  			}
  		}
  		return copy.toArray();
  	}
  
  	// === IFrame implementation ===
  
  	public void accept(final MethodVisitor mv) {
  		if (locals != null) {
  			mv.visitFrame(Opcodes.F_NEW, locals.length, locals, stack.length,
  					stack);
  		}
  	}
  
  }
  