Vault example documents provider.

Example provider that encrypts both metadata and contents of
documents stored inside.  It shows advanced usage of new storage
access APIs and hardware-backed key chain.

Change-Id: I2cdf4e949be8471c3d8b4f45ec0681c9248ea09c

samples/Vault/src/com/example/android/vault/Utils.java

@@ -0,0 +1,72 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * 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.example.android.vault;
+
+import android.os.ParcelFileDescriptor;
+
+import java.io.ByteArrayOutputStream;
+import java.io.Closeable;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+
+public class Utils {
+    public static void closeQuietly(Closeable closable) {
+        if (closable != null) {
+            try {
+                closable.close();
+            } catch (IOException ignored) {
+            }
+        }
+    }
+
+    public static void closeWithErrorQuietly(ParcelFileDescriptor pfd, String msg) {
+        if (pfd != null) {
+            try {
+                pfd.closeWithError(msg);
+            } catch (IOException ignored) {
+            }
+        }
+    }
+
+    public static void writeFully(File file, byte[] data) throws IOException {
+        final OutputStream out = new FileOutputStream(file);
+        try {
+            out.write(data);
+        } finally {
+            out.close();
+        }
+    }
+
+    public static byte[] readFully(File file) throws IOException {
+        final InputStream in = new FileInputStream(file);
+        try {
+            ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+            byte[] buffer = new byte[1024];
+            int count;
+            while ((count = in.read(buffer)) != -1) {
+                bytes.write(buffer, 0, count);
+            }
+            return bytes.toByteArray();
+        } finally {
+            in.close();
+        }
+    }
+}