Data corruption on partially written data

library/src/main/java/com/ironz/binaryprefs/file/adapter/NioFileAdapter.java

@@ -4,6 +4,7 @@
 import com.ironz.binaryprefs.file.directory.DirectoryProvider;
 
 import java.io.File;
+import java.io.IOException;
 import java.io.RandomAccessFile;
 import java.nio.MappedByteBuffer;
 import java.nio.channels.FileChannel;
@@ -16,7 +17,7 @@
  * If adapter detects backup file it will be replaced
  * to original file. See {@link #fetchBackupOrOriginal(String)}.
  */
-public final class NioFileAdapter implements FileAdapter {
+public class NioFileAdapter implements FileAdapter {
 
  private static final String ZERO_BYTES_MESSAGE = "%s key's value is zero bytes for saving";
 
@@ -56,10 +57,18 @@ private byte[] fetchBackupOrOriginal(String name) {
  File backupFile = new File(backupDir, name + BACKUP_EXTENSION);
  File file = new File(baseDir, name);
  if (backupFile.exists()) {
+ restoreBackup(file, backupFile);
+ }
+ return fetchInternal(file);
+ }
+
+ private void restoreBackup(File file, File backupFile) {
+ if (backupFile.length() == 0) {
  delete(file);
+ delete(backupFile);
+ } else {
  swap(backupFile, file);
  }
- return fetchInternal(file);
  }
 
  private byte[] fetchInternal(File file) {
@@ -99,12 +108,14 @@ private void backupAndSave(String name, byte[] bytes) {
  }
  File file = new File(baseDir, name);
  File backupFile = new File(backupDir, name + BACKUP_EXTENSION);
+
+ ensureExists(file);
  swap(file, backupFile);
  saveInternal(file, bytes);
  delete(backupFile);
  }
 
- private void saveInternal(File file, byte[] bytes) {
+ void saveInternal(File file, byte[] bytes) {
  FileChannel channel = null;
  RandomAccessFile randomAccessFile = null;
  try {
@@ -130,6 +141,17 @@ private void saveInternal(File file, byte[] bytes) {
  }
  }
 
+ private void ensureExists(File file) {
+ if (!file.exists()) {
+ try {
+ //noinspection ResultOfMethodCallIgnored
+ file.createNewFile();
+ } catch (IOException e) {
+ throw new FileOperationException(e);
+ }
+ }
+ }
+
  private void swap(File from, File to) {
  if (!from.exists()) {
  return;

library/src/test/java/com/ironz/binaryprefs/file/NioFileAdapterTest.java → library/src/test/java/com/ironz/binaryprefs/file/adapter/NioFileAdapterTest.java

@@ -1,8 +1,6 @@
-package com.ironz.binaryprefs.file;
+package com.ironz.binaryprefs.file.adapter;
 
 import com.ironz.binaryprefs.exception.FileOperationException;
-import com.ironz.binaryprefs.file.adapter.FileAdapter;
-import com.ironz.binaryprefs.file.adapter.NioFileAdapter;
 import com.ironz.binaryprefs.file.directory.DirectoryProvider;
 import org.junit.Before;
 import org.junit.Rule;
@@ -26,6 +24,7 @@ public final class NioFileAdapterTest {
  public final TemporaryFolder folder = new TemporaryFolder();
 
  private FileAdapter fileAdapter;
+ private FileAdapter failingAdapter;
 
  @Before
  public void setUp() throws Exception {
@@ -49,6 +48,14 @@ public File getLockDirectory() {
  }
  };
  fileAdapter = new NioFileAdapter(directoryProvider);
+ failingAdapter = new NioFileAdapter(directoryProvider) {
+ @Override
+ void saveInternal(File file, byte[] bytes) {
+ byte[] successBytes = Arrays.copyOf(bytes, 1);
+ super.saveInternal(file, successBytes);
+ throw new IllegalStateException();
+ }
+ };
  }
 
  @Test
@@ -114,4 +121,26 @@ public void deleteAll() {
  assertNotNull(fileAdapter.fetch(FILE_NAME));
  fileAdapter.fetch(FILE_NAME_1);
  }
-}
+
+ @Test(expected = FileOperationException.class)
+ public void fetchNoFile() {
+ fileAdapter.fetch(FILE_NAME);
+ }
+
+ @Test(expected = IllegalStateException.class)
+ public void failOnSave() {
+ failingAdapter.save(FILE_NAME, bytes);
+ }
+
+ @Test(expected = FileOperationException.class)
+ public void recoverAfterFail() {
+ try {
+ failingAdapter.save(FILE_NAME, bytes);
+ throw new AssertionError();
+ } catch (IllegalStateException ignored) {
+ }
+
+ fileAdapter.fetch(FILE_NAME);
+ }
+
+}