1/*
2 * Copyright (C) 2012 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
17package com.google.dexmaker;
18
19import java.io.File;
20import java.util.ArrayList;
21import java.util.List;
22
23/**
24 * Uses heuristics to guess the application's private data directory.
25 */
26class AppDataDirGuesser {
27    public File guess() {
28        try {
29            ClassLoader classLoader = guessSuitableClassLoader();
30            // Check that we have an instance of the PathClassLoader.
31            Class<?> clazz = Class.forName("dalvik.system.PathClassLoader");
32            clazz.cast(classLoader);
33            // Use the toString() method to calculate the data directory.
34            String pathFromThisClassLoader = getPathFromThisClassLoader(classLoader);
35            File[] results = guessPath(pathFromThisClassLoader);
36            if (results.length > 0) {
37                return results[0];
38            }
39        } catch (ClassCastException ignored) {
40        } catch (ClassNotFoundException ignored) {
41        }
42        return null;
43    }
44
45    private ClassLoader guessSuitableClassLoader() {
46        return AppDataDirGuesser.class.getClassLoader();
47    }
48
49    private String getPathFromThisClassLoader(ClassLoader classLoader) {
50        // Parsing toString() method: yuck.  But no other way to get the path.
51        // Strip out the bit between angle brackets, that's our path.
52        String result = classLoader.toString();
53        int index = result.lastIndexOf('[');
54        result = (index == -1) ? result : result.substring(index + 1);
55        index = result.indexOf(']');
56        return (index == -1) ? result : result.substring(0, index);
57    }
58
59    File[] guessPath(String input) {
60        List<File> results = new ArrayList<File>();
61        for (String potential : input.split(":")) {
62            if (!potential.startsWith("/data/app/")) {
63                continue;
64            }
65            int start = "/data/app/".length();
66            int end = potential.lastIndexOf(".apk");
67            if (end != potential.length() - 4) {
68                continue;
69            }
70            int dash = potential.indexOf("-");
71            if (dash != -1) {
72                end = dash;
73            }
74            File file = new File("/data/data/" + potential.substring(start, end) + "/cache");
75            if (isWriteableDirectory(file)) {
76                results.add(file);
77            }
78        }
79        return results.toArray(new File[results.size()]);
80    }
81
82    boolean isWriteableDirectory(File file) {
83        return file.isDirectory() && file.canWrite();
84    }
85}
86