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:
   *    Evgeny Mandrikov - initial API and implementation
   *
   *******************************************************************************/
  package org.jacoco.core.internal.analysis.filter;
  
  import org.objectweb.asm.Opcodes;
  import org.objectweb.asm.tree.AbstractInsnNode;
  import org.objectweb.asm.tree.JumpInsnNode;
  import org.objectweb.asm.tree.LabelNode;
  import org.objectweb.asm.tree.LookupSwitchInsnNode;
  import org.objectweb.asm.tree.MethodNode;
  import org.objectweb.asm.tree.TableSwitchInsnNode;
  
  /**
   * Filters code that is generated by javac for a switch statement with a String.
   */
  public final class StringSwitchJavacFilter implements IFilter {
  
  	public void filter(final MethodNode methodNode,
  			final IFilterContext context, final IFilterOutput output) {
  		AbstractInsnNode i = methodNode.instructions.getFirst();
  		while (i != null) {
  			filter(i, output);
  			i = i.getNext();
  		}
  	}
  
  	/**
  	 * javac generates two switches. First one by {@link String#hashCode()}.
  	 * Number of handlers in the second switch is equal to number of handlers in
  	 * source code, so it is enough to completely filter-out first switch.
  	 * Handler for default case of the first switch - is the second switch.
  	 */
  	private void filter(final AbstractInsnNode start,
  			final IFilterOutput output) {
  		final LabelNode dflt;
  		if (start.getOpcode() == Opcodes.LOOKUPSWITCH) {
  			dflt = ((LookupSwitchInsnNode) start).dflt;
  		} else if (start.getOpcode() == Opcodes.TABLESWITCH) {
  			dflt = ((TableSwitchInsnNode) start).dflt;
  		} else {
  			return;
  		}
  		if (new Matcher().match(start, dflt)) {
  			output.ignore(start, dflt);
  		}
  	}
  
  	private static class Matcher extends AbstractMatcher {
  		boolean match(final AbstractInsnNode start,
  				final AbstractInsnNode secondSwitchLabel) {
  			cursor = start;
  			for (int i = 0; cursor != null && i < 4; i++) {
  				cursor = cursor.getPrevious();
  			}
  			if (cursor == null || cursor.getOpcode() != Opcodes.ICONST_M1) {
  				return false;
  			}
  			nextIsVar(Opcodes.ISTORE, "c");
  			// Even if expression is not a variable, its result will be
  			// precomputed before the previous two instructions:
  			nextIsVar(Opcodes.ALOAD, "s");
  			nextIsInvoke(Opcodes.INVOKEVIRTUAL, "java/lang/String", "hashCode",
  					"()I");
  			next();
  			while (true) {
  				nextIsVar(Opcodes.ALOAD, "s");
  				nextIs(Opcodes.LDC);
  				nextIsInvoke(Opcodes.INVOKEVIRTUAL, "java/lang/String",
  						"equals", "(Ljava/lang/Object;)Z");
  				// jump to next comparison or second switch
  				nextIs(Opcodes.IFEQ);
  				// ICONST, BIPUSH or SIPUSH
  				next();
  				nextIsVar(Opcodes.ISTORE, "c");
  				if (cursor == null) {
  					return false;
  				}
  				if (cursor.getNext() == secondSwitchLabel) {
  					break;
  				}
  				nextIs(Opcodes.GOTO);
  				if (((JumpInsnNode) cursor).label != secondSwitchLabel) {
  					return false;
  				}
  			}
  			nextIsVar(Opcodes.ILOAD, "c");
  			// Can be TABLESWITCH or LOOKUPSWITCH depending on number of cases
  			nextIsSwitch();
  			return cursor != null;
  		}
  	}
  
  }
  