| /* |
| * Copyright 2022 Google LLC |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package com.google.android.libraries.mobiledatadownload.file.openers; |
| |
| import com.google.android.libraries.mobiledatadownload.file.OpenContext; |
| import com.google.android.libraries.mobiledatadownload.file.Opener; |
| import com.google.android.libraries.mobiledatadownload.file.common.FileChannelConvertible; |
| import com.google.android.libraries.mobiledatadownload.file.common.UnsupportedFileStorageOperation; |
| import java.io.IOException; |
| import java.io.InputStream; |
| import java.nio.MappedByteBuffer; |
| import java.nio.channels.FileChannel; |
| import java.nio.channels.FileChannel.MapMode; |
| |
| /** |
| * Opener that maps a file directly into memory (read only). |
| * |
| * <p>Warning: MappedByteBuffer is known to suffer from poor garbage collection; see {@link |
| * <internal>}. |
| * |
| * <p>Usage: <code> |
| * MappedByteBuffer buffer = storage.open(uri, MappedByteBufferOpener.create()); |
| * </code> |
| */ |
| public final class MappedByteBufferOpener implements Opener<MappedByteBuffer> { |
| |
| private MappedByteBufferOpener() {} |
| |
| public static MappedByteBufferOpener createForRead() { |
| return new MappedByteBufferOpener(); |
| } |
| |
| @Override |
| public MappedByteBuffer open(OpenContext openContext) throws IOException { |
| // FileChannelConvertible (vs ReadFileOpener) allows this opener to be used over IPC. |
| try (InputStream stream = ReadStreamOpener.create().open(openContext)) { |
| if (stream instanceof FileChannelConvertible) { |
| FileChannel fileChannel = ((FileChannelConvertible) stream).toFileChannel(); |
| return fileChannel.map(MapMode.READ_ONLY, 0, fileChannel.size()); |
| } |
| throw new UnsupportedFileStorageOperation( |
| "URI not convertible to FileChannel for mapping: " + openContext.originalUri()); |
| } |
| } |
| } |