/*

  * 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 org.apache.commons.classscan.util;

 public abstract class CallStack {

     interface GetCallerStrategy {

         Class<?> getCallerClass(int callStackDepth);        

     }

     private static GetCallerStrategy strategy;

     static class SunReflection implements GetCallerStrategy {

         SunReflection() {

             // cause load of sun.reflect.Reflection class

             sun.reflect.Reflection.getCallerClass(0);

         }

         @Override

         public Class<?> getCallerClass(int callStackDepth) {

             return sun.reflect.Reflection.getCallerClass(callStackDepth);

         }

     }

     static class SecurityManagerMethod extends SecurityManager implements GetCallerStrategy {

         @Override

         public Class<?> getCallerClass(int callStackDepth) {

             return getClassContext()[callStackDepth];

         }

     }

     static {

         try {

             strategy= new SunReflection();

         }

         catch(Throwable t) {

             strategy= new SecurityManagerMethod();

         }

     }

     /**

      * Return the Class of the caller.

      * @param callStackDepth The number of stack frames to skip.  

      * A value of 0 will return the calling Class of this method.  

      * A value of 1 will return the calling Class of the caller of this method. 

      * @return The Class at callStackDepth down the call stack

      */

     public static Class<?> getCallerClass(int callStackDepth) {

         return strategy.getCallerClass(callStackDepth+3);

     }

     /**

      * Return the ClassLoader of the caller.

      * @param callStackDepth The number of stack frames to skip.  

      * A value of 0 will return the ClassLoader of the calling Class of this method.  

      * A value of 1 will return the ClassLoader of the calling Class of the caller of this method. 

      * @return The ClassLoader of the Class at callStackDepth down the call stack

      */

     public static ClassLoader getClassLoader(int callStackDepth) {

         Class<?> rc= strategy.getCallerClass(callStackDepth+3);

         return rc.getClassLoader();

     }

 }