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      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 
     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      */
     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      */
     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      */
     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
     94     public boolean onCreate() {
     95         return true;
     96     }
     97 
     98     @Override
     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
    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 
    122     protected static String getExtensionFromUri(final Uri uri) {
    123         return uri.getQueryParameter(FILE_EXTENSION_PARAM_KEY);
    124     }
    125 
    126     @Override
    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
    134     public Uri insert(final Uri uri, final ContentValues values) {
    135         // Don't support inserts.
    136         return null;
    137     }
    138 
    139     @Override
    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
    147     public String getType(final Uri uri) {
    148         // No need for mime types.
    149         return null;
    150     }
    151 }
    152