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 android.util.Pair; 20 import com.google.android.libraries.mobiledatadownload.file.OpenContext; 21 import com.google.android.libraries.mobiledatadownload.file.Opener; 22 import java.io.Closeable; 23 import java.io.IOException; 24 25 /** 26 * An opener that produces a file descriptor URI (like "fd:123"). This is useful for opening a file 27 * in Java and passing a handle to it down to C++. 28 * 29 * <p>Transforms are not applied in the Java code and are retained in the returned URI so they can 30 * be applied in native code. 31 * 32 * <p>The caller is responsible for closing the file descriptor. The native code is expected to dup 33 * the descriptor if it needs to hold it, so they can both call close independently. 34 * 35 * <p>Usage: <code> 36 * try (CloseableUri fdUri = storage.open(uri, NativeReadOpener.create())) { 37 * // Use URI in native code 38 * } 39 * </code> 40 */ 41 public final class NativeReadOpener implements Opener<CloseableUri> { NativeReadOpener()42 private NativeReadOpener() {} 43 create()44 public static NativeReadOpener create() { 45 return new NativeReadOpener(); 46 } 47 48 @Override open(OpenContext openContext)49 public CloseableUri open(OpenContext openContext) throws IOException { 50 Pair<Uri, Closeable> result = openContext.backend().openForNativeRead(openContext.encodedUri()); 51 Uri uriWithFragment = 52 result 53 .first 54 .buildUpon() 55 .encodedFragment(openContext.originalUri().getEncodedFragment()) 56 .build(); 57 return new CloseableUri() { 58 @Override 59 public Uri uri() { 60 return uriWithFragment; 61 } 62 63 @Override 64 public void close() throws IOException { 65 result.second.close(); 66 } 67 }; 68 } 69 } 70