load entropy data at boot. Periodically write entropy data to disk.
diff --git a/services/java/com/android/server/RandomBlock.java b/services/java/com/android/server/RandomBlock.java
new file mode 100644
index 0000000..c08761e
--- /dev/null
+++ b/services/java/com/android/server/RandomBlock.java
@@ -0,0 +1,90 @@
+/*
+ * Copyright (C) 2009 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.android.server;
+
+import android.util.Log;
+
+import java.io.Closeable;
+import java.io.EOFException;
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+
+/**
+ * A 4k block of random {@code byte}s.
+ */
+class RandomBlock {
+
+ private static final String TAG = "RandomBlock";
+ private static final int BLOCK_SIZE = 4096;
+ private byte[] block = new byte[BLOCK_SIZE];
+
+ private RandomBlock() { }
+
+ static RandomBlock fromFile(String filename) throws IOException {
+ Log.v(TAG, "reading from file " + filename);
+ InputStream stream = null;
+ try {
+ stream = new FileInputStream(filename);
+ return fromStream(stream);
+ } finally {
+ close(stream);
+ }
+ }
+
+ private static RandomBlock fromStream(InputStream in) throws IOException {
+ RandomBlock retval = new RandomBlock();
+ int total = 0;
+ while(total < BLOCK_SIZE) {
+ int result = in.read(retval.block, total, BLOCK_SIZE - total);
+ if (result == -1) {
+ throw new EOFException();
+ }
+ total += result;
+ }
+ return retval;
+ }
+
+ void toFile(String filename) throws IOException {
+ Log.v(TAG, "writing to file " + filename);
+ OutputStream out = null;
+ try {
+ // TODO: Investigate using RandomAccessFile
+ out = new FileOutputStream(filename);
+ toStream(out);
+ } finally {
+ close(out);
+ }
+ }
+
+ private void toStream(OutputStream out) throws IOException {
+ out.write(block);
+ }
+
+ private static void close(Closeable c) {
+ try {
+ if (c == null) {
+ return;
+ }
+ c.close();
+ } catch (IOException e) {
+ Log.w(TAG, "IOException thrown while closing Closeable", e);
+ }
+ }
+}