1 /* 2 * Copyright 2022 Google LLC 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 package com.google.android.libraries.mobiledatadownload.file.openers; 17 18 import android.net.Uri; 19 import com.google.android.libraries.mobiledatadownload.file.OpenContext; 20 import com.google.android.libraries.mobiledatadownload.file.Opener; 21 import com.google.android.libraries.mobiledatadownload.file.SynchronousFileStorage; 22 import com.google.common.collect.Iterables; 23 import java.io.FileNotFoundException; 24 import java.io.IOException; 25 import java.util.ArrayDeque; 26 import java.util.Deque; 27 28 /** 29 * Calculates the size of a directory by recursively summing the size of all of its children. If the 30 * Uri refers to an empty directory, returns 0. If the Uri refers to a file or does not exist, 31 * throws {@link FileNotFoundException}. 32 * 33 * <p>WARNING: this opener suffers from the following caveats and should be used with caution: 34 * 35 * <ul> 36 * <li>Directory tree traversal is not an atomic operation 37 * <li>There are no special considerations for symlinks, meaning the opener could get caught in a 38 * recursive directory loop (i.e. a directory that contains a symlink to itself) 39 * <li>Fails fast if there is an I/O error while processing a given child Uri 40 * </ul> 41 * 42 * <p>Usage: long size = storage.open(uri, RecursiveSizeOpener.create()); 43 */ 44 public final class RecursiveSizeOpener implements Opener<Long> { RecursiveSizeOpener()45 private RecursiveSizeOpener() {} 46 create()47 public static RecursiveSizeOpener create() { 48 return new RecursiveSizeOpener(); 49 } 50 51 @Override open(OpenContext context)52 public Long open(OpenContext context) throws IOException { 53 long totalSize = 0; 54 Deque<Uri> toProcess = new ArrayDeque<>(); 55 SynchronousFileStorage storage = context.storage(); 56 57 // Stripping the Uri fragment means children filenames don't get encoded by transforms. This is 58 // intentional: we're simply calculating the total file size regardless of the "correct" names. 59 // Children API call throws FNF if the Uri is a file or does not exist. 60 Uri uriWithoutFragment = context.originalUri().buildUpon().fragment(null).build(); 61 Iterables.addAll(toProcess, storage.children(uriWithoutFragment)); 62 63 // NOTE: breadth-first traversal is an arbitrary implementation choice 64 while (!toProcess.isEmpty()) { 65 Uri uri = toProcess.remove(); 66 if (storage.isDirectory(uri)) { 67 Iterables.addAll(toProcess, storage.children(uri)); 68 } else if (storage.exists(uri)) { 69 totalSize += storage.fileSize(uri); 70 } else { 71 throw new FileNotFoundException(String.format("Child %s could not be opened", uri)); 72 } 73 } 74 75 return totalSize; 76 } 77 } 78