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 
sharedFactory()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      */
addFilterLibrary(String libraryPath)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 
addPackage(String packageName)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 
isFilterAvailable(String className)83     public boolean isFilterAvailable(String className) {
84         return getFilterClass(className) != null;
85     }
86 
createFilterByClassName(String className, String filterName, MffContext context)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 
createFilterByClass(Class<? extends Filter> filterClass, String filterName, MffContext context)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 
getFilterClass(String name)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