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.Behavior; 20 import com.google.android.libraries.mobiledatadownload.file.OpenContext; 21 import com.google.android.libraries.mobiledatadownload.file.Opener; 22 import com.google.errorprone.annotations.CanIgnoreReturnValue; 23 import com.google.protobuf.MessageLite; 24 import java.io.FileNotFoundException; 25 import java.io.IOException; 26 import java.io.OutputStream; 27 import java.util.List; 28 29 /** Writes a proto to a file atomically. */ 30 public final class WriteProtoOpener implements Opener<Void> { 31 32 private final MessageLite proto; 33 private Behavior[] behaviors; 34 WriteProtoOpener(MessageLite proto)35 private WriteProtoOpener(MessageLite proto) { 36 this.proto = proto; 37 } 38 create(MessageLite proto)39 public static WriteProtoOpener create(MessageLite proto) { 40 return new WriteProtoOpener(proto); 41 } 42 43 /** 44 * Supports adding options to writes. For example, SyncBehavior will force data to be flushed and 45 * durably persisted. 46 */ 47 @CanIgnoreReturnValue withBehaviors(Behavior... behaviors)48 public WriteProtoOpener withBehaviors(Behavior... behaviors) { 49 this.behaviors = behaviors; 50 return this; 51 } 52 53 @Override open(OpenContext openContext)54 public Void open(OpenContext openContext) throws IOException { 55 Uri tempUri = ScratchFile.scratchUri(openContext.encodedUri()); 56 OutputStream backendOutput = openContext.backend().openForWrite(tempUri); 57 List<OutputStream> chain = openContext.chainTransformsForWrite(backendOutput); 58 if (behaviors != null) { 59 for (Behavior behavior : behaviors) { 60 behavior.forOutputChain(chain); 61 } 62 } 63 try (OutputStream out = chain.get(0)) { 64 proto.writeTo(out); 65 if (behaviors != null) { 66 for (Behavior behavior : behaviors) { 67 behavior.commit(); 68 } 69 } 70 } catch (Exception ex) { 71 try { 72 openContext.backend().deleteFile(tempUri); 73 } catch (FileNotFoundException ex2) { 74 // Ignore. 75 } 76 if (ex instanceof IOException) { 77 throw (IOException) ex; 78 } 79 throw new IOException(ex); 80 } 81 openContext.backend().rename(tempUri, openContext.encodedUri()); 82 return null; 83 } 84 } 85