javatests/com/google/android/libraries/mobiledatadownload/file/openers/NativeReadOpenerAndroidTest.java

/*
 * 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 static com.google.android.libraries.mobiledatadownload.file.common.testing.StreamUtils.createFile;
import static com.google.common.truth.Truth.assertThat;
import static java.nio.charset.StandardCharsets.UTF_8;
import static org.junit.Assert.assertThrows;

import android.net.Uri;
import com.google.android.libraries.mobiledatadownload.file.SynchronousFileStorage;
import com.google.android.libraries.mobiledatadownload.file.backends.FileDescriptorUri;
import com.google.android.libraries.mobiledatadownload.file.backends.JavaFileBackend;
import com.google.android.libraries.mobiledatadownload.file.common.testing.FileDescriptorLeakChecker;
import com.google.android.libraries.mobiledatadownload.file.common.testing.TemporaryUri;
import com.google.common.collect.ImmutableList;
import com.google.common.io.CharStreams;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import org.junit.Before;
import org.junit.Rule;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.JUnit4;

@RunWith(JUnit4.class)
public final class NativeReadOpenerAndroidTest {

  private SynchronousFileStorage storage;

  @Rule public FileDescriptorLeakChecker leakChecker = new FileDescriptorLeakChecker();
  @Rule public TemporaryUri tmpUri = new TemporaryUri();

  @Before
  public void initStorage() throws Exception {
    storage = new SynchronousFileStorage(ImmutableList.of(new JavaFileBackend()));
  }

  @Test
  public void openForNativeRead_returnsAWorkingFileDescriptor() throws Exception {
    Uri uri = tmpUri.newUri();
    createFile(storage, uri, "content");
    CloseableUri result = storage.open(uri, NativeReadOpener.create());

    assertThat(result.uri().getScheme()).isEqualTo("fd");
    assertThat(FileDescriptorUri.getFd(result.uri())).isGreaterThan(0);

    // Use proc filesystem to verify data.
    File fdFile = new File("/proc/self/fd/" + result.uri().getSchemeSpecificPart());
    InputStream in = new FileInputStream(fdFile);
    Reader reader = new InputStreamReader(in, UTF_8);
    assertThat(CharStreams.toString(reader)).isEqualTo("content");

    // Verify closing behavior.
    assertThat(fdFile.exists()).isTrue();
    reader.close(); // This won't actually close the fd.
    assertThat(fdFile.exists()).isTrue();
    result.close(); // This does.
    assertThat(fdFile.exists()).isFalse();
  }

  @Test
  public void openForNativeRead_withMissingFile_throwsFileNotFound() throws Exception {
    Uri uri = Uri.parse("file:/does-not-exist");
    assertThrows(FileNotFoundException.class, () -> storage.open(uri, NativeReadOpener.create()));
  }
}