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.lang.reflect.Field;
21import java.util.ArrayList;
22import java.util.List;
23
24/**
25 * Uses heuristics to guess the application's private data directory.
26 */
27class AppDataDirGuesser {
28    public File guess() {
29        try {
30            ClassLoader classLoader = guessSuitableClassLoader();
31            // Check that we have an instance of the PathClassLoader.
32            Class<?> clazz = Class.forName("dalvik.system.PathClassLoader");
33            clazz.cast(classLoader);
34            // Use the toString() method to calculate the data directory.
35            String pathFromThisClassLoader = getPathFromThisClassLoader(classLoader, clazz);
36            File[] results = guessPath(pathFromThisClassLoader);
37            if (results.length > 0) {
38                return results[0];
39            }
40        } catch (ClassCastException ignored) {
41        } catch (ClassNotFoundException ignored) {
42        }
43        return null;
44    }
45
46    private ClassLoader guessSuitableClassLoader() {
47        return AppDataDirGuesser.class.getClassLoader();
48    }
49
50    private String getPathFromThisClassLoader(ClassLoader classLoader,
51            Class<?> pathClassLoaderClass) {
52        // Prior to ICS, we can simply read the "path" field of the
53        // PathClassLoader.
54        try {
55            Field pathField = pathClassLoaderClass.getDeclaredField("path");
56            pathField.setAccessible(true);
57            return (String) pathField.get(classLoader);
58        } catch (NoSuchFieldException ignored) {
59        } catch (IllegalAccessException ignored) {
60        } catch (ClassCastException ignored) {
61        }
62
63        // Parsing toString() method: yuck.  But no other way to get the path.
64        String result = classLoader.toString();
65        return processClassLoaderString(result);
66    }
67
68    /**
69     * Given the result of a ClassLoader.toString() call, process the result so that guessPath
70     * can use it. There are currently two variants. For Android 4.3 and later, the string
71     * "DexPathList" should be recognized and the array of dex path elements is parsed. for
72     * earlier versions, the last nested array ('[' ... ']') is enclosing the string we are
73     * interested in.
74     */
75    static String processClassLoaderString(String input) {
76        if (input.contains("DexPathList")) {
77            return processClassLoaderString43OrLater(input);
78        } else {
79            return processClassLoaderString42OrEarlier(input);
80        }
81    }
82
83    private static String processClassLoaderString42OrEarlier(String input) {
84        /* The toString output looks like this:
85         * dalvik.system.PathClassLoader[dexPath=path/to/apk,libraryPath=path/to/libs]
86         */
87        int index = input.lastIndexOf('[');
88        input = (index == -1) ? input : input.substring(index + 1);
89        index = input.indexOf(']');
90        input = (index == -1) ? input : input.substring(0, index);
91        return input;
92    }
93
94    private static String processClassLoaderString43OrLater(String input) {
95        /* The toString output looks like this:
96         * dalvik.system.PathClassLoader[DexPathList[[zip file "/data/app/{NAME}", ...], nativeLibraryDirectories=[...]]]
97         */
98        int start = input.indexOf("DexPathList") + "DexPathList".length();
99        if (input.length() > start + 4) {  // [[ + ]]
100            String trimmed = input.substring(start);
101            int end = trimmed.indexOf(']');
102            if (trimmed.charAt(0) == '[' && trimmed.charAt(1) == '[' && end >= 0) {
103                trimmed = trimmed.substring(2, end);
104                // Comma-separated list, Arrays.toString output.
105                String split[] = trimmed.split(",");
106
107                // Clean up parts. Each path element is the type of the element plus the path in
108                // quotes.
109                for (int i = 0; i < split.length; i++) {
110                    int quoteStart = split[i].indexOf('"');
111                    int quoteEnd = split[i].lastIndexOf('"');
112                    if (quoteStart > 0 && quoteStart < quoteEnd) {
113                        split[i] = split[i].substring(quoteStart + 1, quoteEnd);
114                    }
115                }
116
117                // Need to rejoin components.
118                StringBuilder sb = new StringBuilder();
119                for (String s : split) {
120                    if (sb.length() > 0) {
121                        sb.append(':');
122                    }
123                    sb.append(s);
124                }
125                return sb.toString();
126            }
127        }
128
129        // This is technically a parsing failure. Return the original string, maybe a later
130        // stage can still salvage this.
131        return input;
132    }
133
134    File[] guessPath(String input) {
135        List<File> results = new ArrayList<File>();
136        for (String potential : splitPathList(input)) {
137            if (!potential.startsWith("/data/app/")) {
138                continue;
139            }
140            int start = "/data/app/".length();
141            int end = potential.lastIndexOf(".apk");
142            if (end != potential.length() - 4) {
143                continue;
144            }
145            int dash = potential.indexOf("-");
146            if (dash != -1) {
147                end = dash;
148            }
149            String packageName = potential.substring(start, end);
150            File dataDir = new File("/data/data/" + packageName);
151            if (isWriteableDirectory(dataDir)) {
152                File cacheDir = new File(dataDir, "cache");
153                // The cache directory might not exist -- create if necessary
154                if (fileOrDirExists(cacheDir) || cacheDir.mkdir()) {
155                    if (isWriteableDirectory(cacheDir)) {
156                        results.add(cacheDir);
157                    }
158                }
159            }
160        }
161        return results.toArray(new File[results.size()]);
162    }
163
164    static String[] splitPathList(String input) {
165       String trimmed = input;
166       if (input.startsWith("dexPath=")) {
167            int start = "dexPath=".length();
168            int end = input.indexOf(',');
169
170           trimmed = (end == -1) ? input.substring(start) : input.substring(start, end);
171       }
172
173       return trimmed.split(":");
174    }
175
176    boolean fileOrDirExists(File file) {
177        return file.exists();
178    }
179
180    boolean isWriteableDirectory(File file) {
181        return file.isDirectory() && file.canWrite();
182    }
183}
184