1 /*
2  * Copyright (C) 2015 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 package com.android.messaging.datamodel;
18 
19 import android.content.ContentProvider;
20 import android.content.ContentResolver;
21 import android.content.ContentValues;
22 import android.database.Cursor;
23 import android.net.Uri;
24 import android.os.ParcelFileDescriptor;
25 import android.text.TextUtils;
26 
27 import java.io.File;
28 import java.io.FileNotFoundException;
29 import java.io.IOException;
30 import java.util.Random;
31 
32 /**
33  * A very simple content provider that can serve files.
34  */
35 public abstract class FileProvider extends ContentProvider {
36     // Object to generate random id for temp images.
37     private static final Random RANDOM_ID = new Random();
38 
getFile(final String path, final String extension)39     abstract File getFile(final String path, final String extension);
40 
41     private static final String FILE_EXTENSION_PARAM_KEY = "ext";
42 
43     /**
44      * Check if filename conforms to requirement for our provider
45      * @param fileId filename (optionally starting with path character
46      * @return true if filename consists only of digits
47      */
isValidFileId(final String fileId)48     protected static boolean isValidFileId(final String fileId) {
49         // Ignore initial "/"
50         for (int index = (fileId.startsWith("/") ? 1 : 0); index < fileId.length(); index++) {
51             final Character c = fileId.charAt(index);
52             if (!Character.isDigit(c)) {
53                 return false;
54             }
55         }
56         return true;
57     }
58 
59     /**
60      * Create a temp file (to allow writing to that one particular file)
61      * @param file the file to create
62      * @return true if file successfully created
63      */
ensureFileExists(final File file)64     protected static boolean ensureFileExists(final File file) {
65         try {
66             final File parentDir = file.getParentFile();
67             if (parentDir.exists() || parentDir.mkdirs()) {
68                 return file.createNewFile();
69             }
70         } catch (final IOException e) {
71             // fail on exceptions creating the file
72         }
73         return false;
74     }
75 
76     /**
77      * Build uri for a new temporary file (creating file)
78      * @param authority authority with which to populate uri
79      * @param extension optional file extension
80      * @return unique uri that can be used to write temporary files
81      */
buildFileUri(final String authority, final String extension)82     protected static Uri buildFileUri(final String authority, final String extension) {
83         final long fileId = Math.abs(RANDOM_ID.nextLong());
84         final Uri.Builder builder = (new Uri.Builder()).authority(authority).scheme(
85                 ContentResolver.SCHEME_CONTENT);
86         builder.appendPath(String.valueOf(fileId));
87         if (!TextUtils.isEmpty(extension)) {
88             builder.appendQueryParameter(FILE_EXTENSION_PARAM_KEY, extension);
89         }
90         return builder.build();
91     }
92 
93     @Override
onCreate()94     public boolean onCreate() {
95         return true;
96     }
97 
98     @Override
delete(final Uri uri, final String selection, final String[] selectionArgs)99     public int delete(final Uri uri, final String selection, final String[] selectionArgs) {
100         final String fileId = uri.getPath();
101         if (isValidFileId(fileId)) {
102             final File file = getFile(fileId, getExtensionFromUri(uri));
103             return file.delete() ? 1 : 0;
104         }
105         return 0;
106     }
107 
108     @Override
openFile(final Uri uri, final String fileMode)109     public ParcelFileDescriptor openFile(final Uri uri, final String fileMode)
110             throws FileNotFoundException {
111         final String fileId = uri.getPath();
112         if (isValidFileId(fileId)) {
113             final File file = getFile(fileId, getExtensionFromUri(uri));
114             final int mode =
115                     (TextUtils.equals(fileMode, "r") ? ParcelFileDescriptor.MODE_READ_ONLY :
116                         ParcelFileDescriptor.MODE_WRITE_ONLY | ParcelFileDescriptor.MODE_TRUNCATE);
117             return ParcelFileDescriptor.open(file, mode);
118         }
119         return null;
120     }
121 
getExtensionFromUri(final Uri uri)122     protected static String getExtensionFromUri(final Uri uri) {
123         return uri.getQueryParameter(FILE_EXTENSION_PARAM_KEY);
124     }
125 
126     @Override
query(final Uri uri, final String[] projection, final String selection, final String[] selectionArgs, final String sortOrder)127     public Cursor query(final Uri uri, final String[] projection, final String selection,
128             final String[] selectionArgs, final String sortOrder) {
129         // Don't support queries.
130         return null;
131     }
132 
133     @Override
insert(final Uri uri, final ContentValues values)134     public Uri insert(final Uri uri, final ContentValues values) {
135         // Don't support inserts.
136         return null;
137     }
138 
139     @Override
update(final Uri uri, final ContentValues values, final String selection, final String[] selectionArgs)140     public int update(final Uri uri, final ContentValues values, final String selection,
141             final String[] selectionArgs) {
142         // Don't support updates.
143         return 0;
144     }
145 
146     @Override
getType(final Uri uri)147     public String getType(final Uri uri) {
148         // No need for mime types.
149         return null;
150     }
151 }
152