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      1 /*
      2  * Copyright (C) 2011 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *            http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 
     18 package androidx.media.filterfw;
     19 
     20 import android.util.Log;
     21 
     22 import dalvik.system.PathClassLoader;
     23 
     24 import java.lang.reflect.Constructor;
     25 import java.util.HashSet;
     26 
     27 public class FilterFactory {
     28 
     29     private static FilterFactory mSharedFactory;
     30     private HashSet<String> mPackages = new HashSet<String>();
     31 
     32     private static ClassLoader mCurrentClassLoader;
     33     private static HashSet<String> mLibraries;
     34     private static Object mClassLoaderGuard;
     35 
     36     static {
     37         mCurrentClassLoader = Thread.currentThread().getContextClassLoader();
     38         mLibraries = new HashSet<String>();
     39         mClassLoaderGuard = new Object();
     40     }
     41 
     42     private static final String TAG = "FilterFactory";
     43     private static boolean mLogVerbose = Log.isLoggable(TAG, Log.VERBOSE);
     44 
     45     public static FilterFactory sharedFactory() {
     46         if (mSharedFactory == null) {
     47             mSharedFactory = new FilterFactory();
     48         }
     49         return mSharedFactory;
     50     }
     51 
     52     /**
     53      * Adds a new Java library to the list to be scanned for filters.
     54      * libraryPath must be an absolute path of the jar file.  This needs to be
     55      * static because only one classloader per process can open a shared native
     56      * library, which a filter may well have.
     57      */
     58     public static void addFilterLibrary(String libraryPath) {
     59         if (mLogVerbose) Log.v(TAG, "Adding filter library " + libraryPath);
     60         synchronized(mClassLoaderGuard) {
     61             if (mLibraries.contains(libraryPath)) {
     62                 if (mLogVerbose) Log.v(TAG, "Library already added");
     63                 return;
     64             }
     65             mLibraries.add(libraryPath);
     66             // Chain another path loader to the current chain
     67             mCurrentClassLoader = new PathClassLoader(libraryPath, mCurrentClassLoader);
     68         }
     69     }
     70 
     71     public void addPackage(String packageName) {
     72         if (mLogVerbose) Log.v(TAG, "Adding package " + packageName);
     73         /* TODO: This should use a getPackage call in the caller's context, but no such method
     74                  exists.
     75         Package pkg = Package.getPackage(packageName);
     76         if (pkg == null) {
     77             throw new IllegalArgumentException("Unknown filter package '" + packageName + "'!");
     78         }
     79         */
     80         mPackages.add(packageName);
     81     }
     82 
     83     public boolean isFilterAvailable(String className) {
     84         return getFilterClass(className) != null;
     85     }
     86 
     87     public Filter createFilterByClassName(String className, String filterName, MffContext context) {
     88         if (mLogVerbose) Log.v(TAG, "Looking up class " + className);
     89         Class<? extends Filter> filterClass = getFilterClass(className);
     90         if (filterClass == null) {
     91             throw new IllegalArgumentException("Unknown filter class '" + className + "'!");
     92         }
     93         return createFilterByClass(filterClass, filterName, context);
     94     }
     95 
     96     public Filter createFilterByClass(Class<? extends Filter> filterClass,
     97             String filterName, MffContext context) {
     98         // Look for the correct constructor
     99         Constructor<? extends Filter> filterConstructor = null;
    100         try {
    101             filterConstructor = filterClass.getConstructor(MffContext.class, String.class);
    102         } catch (NoSuchMethodException e) {
    103             throw new IllegalArgumentException("The filter class '" + filterClass
    104                 + "' does not have a constructor of the form <init>(MffContext, String)!");
    105         }
    106 
    107         // Construct the filter
    108         Filter filter = null;
    109         try {
    110             filter = filterConstructor.newInstance(context, filterName);
    111         } catch (Throwable t) {
    112             throw new RuntimeException("Error creating filter " + filterName + "!", t);
    113         }
    114 
    115         if (filter == null) {
    116             throw new IllegalArgumentException("Could not construct the filter '"
    117                 + filterName + "'!");
    118         }
    119         return filter;
    120     }
    121 
    122     private Class<? extends Filter> getFilterClass(String name) {
    123         Class<?> filterClass = null;
    124 
    125         // Look for the class in the imported packages
    126         for (String packageName : mPackages) {
    127             try {
    128                 if (mLogVerbose) Log.v(TAG, "Trying "+ packageName + "." + name);
    129                 synchronized(mClassLoaderGuard) {
    130                     filterClass = mCurrentClassLoader.loadClass(packageName + "." + name);
    131                 }
    132             } catch (ClassNotFoundException e) {
    133                 continue;
    134             }
    135             // Exit loop if class was found.
    136             if (filterClass != null) {
    137                 break;
    138             }
    139         }
    140         Class<? extends Filter> result = null;
    141         try {
    142             if (filterClass != null) {
    143                 result = filterClass.asSubclass(Filter.class);
    144             }
    145         } catch (ClassCastException e) {
    146             // Leave result == null
    147         }
    148         return result;
    149     }
    150 }
    151