001// ***************************************************************************************************************************
002// * Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements.  See the NOTICE file *
003// * distributed with this work for additional information regarding copyright ownership.  The ASF licenses this file        *
004// * to you under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance            *
005// * with the License.  You may obtain a copy of the License at                                                              *
006// *                                                                                                                         *
007// *  http://www.apache.org/licenses/LICENSE-2.0                                                                             *
008// *                                                                                                                         *
009// * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an  *
010// * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the License for the        *
011// * specific language governing permissions and limitations under the License.                                              *
012// ***************************************************************************************************************************
013package org.apache.juneau.mstat;
014
015import java.util.*;
016
017/**
018 * Stack trace utility methods.
019 */
020public class ExceptionHasher {
021
022   private final String stopClass;
023
024   /**
025    * TODO
026    *
027    * @param stopClass TODO
028    */
029   public ExceptionHasher(Class<?> stopClass) {
030      this.stopClass = stopClass == null ? null : stopClass.getName();
031   }
032
033   /**
034    * Calculates a 16-bit hash for the specified throwable based on it's stack trace.
035    *
036    * @param t The throwable to calculate the stack trace on.
037    * @return A calculated hash.
038    */
039   public int hash(Throwable t) {
040      int i = 0;
041      while (t != null) {
042         for (StackTraceElement e : t.getStackTrace()) {
043            if (e.getClassName().equals(stopClass))
044               break;
045            if (e.getClassName().indexOf('$') == -1)
046               i ^= e.hashCode();
047         }
048         t = t.getCause();
049      }
050      return i;
051   }
052
053   /**
054    * TODO
055    *
056    * @param t TODO
057    * @return TODO
058    */
059   public List<StackTraceElement> getStackTrace(Throwable t) {
060      List<StackTraceElement> l = new ArrayList<>();
061      for (StackTraceElement e : t.getStackTrace()) {
062         if (e.getClassName().equals(stopClass))
063            break;
064         l.add(e);
065      }
066      return Collections.unmodifiableList(l);
067   }
068}