| /* |
| * Copyright (C) 2011 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 android.util; |
| |
| import android.net.SntpClient; |
| import android.os.SystemClock; |
| |
| /** |
| * {@link TrustedTime} that connects with a remote NTP server as its remote |
| * trusted time source. |
| * |
| * @hide |
| */ |
| public class NtpTrustedTime implements TrustedTime { |
| private String mNtpServer; |
| private long mNtpTimeout; |
| |
| private boolean mHasCache; |
| private long mCachedNtpTime; |
| private long mCachedNtpElapsedRealtime; |
| private long mCachedNtpCertainty; |
| |
| public NtpTrustedTime() { |
| } |
| |
| public void setNtpServer(String server, long timeout) { |
| mNtpServer = server; |
| mNtpTimeout = timeout; |
| } |
| |
| /** {@inheritDoc} */ |
| public boolean forceRefresh() { |
| if (mNtpServer == null) { |
| // missing server, so no trusted time available |
| return false; |
| } |
| |
| final SntpClient client = new SntpClient(); |
| if (client.requestTime(mNtpServer, (int) mNtpTimeout)) { |
| mHasCache = true; |
| mCachedNtpTime = client.getNtpTime(); |
| mCachedNtpElapsedRealtime = client.getNtpTimeReference(); |
| mCachedNtpCertainty = client.getRoundTripTime() / 2; |
| return true; |
| } else { |
| return false; |
| } |
| } |
| |
| /** {@inheritDoc} */ |
| public boolean hasCache() { |
| return mHasCache; |
| } |
| |
| /** {@inheritDoc} */ |
| public long getCacheAge() { |
| if (mHasCache) { |
| return SystemClock.elapsedRealtime() - mCachedNtpElapsedRealtime; |
| } else { |
| return Long.MAX_VALUE; |
| } |
| } |
| |
| /** {@inheritDoc} */ |
| public long getCacheCertainty() { |
| if (mHasCache) { |
| return mCachedNtpCertainty; |
| } else { |
| return Long.MAX_VALUE; |
| } |
| } |
| |
| /** {@inheritDoc} */ |
| public long currentTimeMillis() { |
| if (!mHasCache) { |
| throw new IllegalStateException("Missing authoritative time source"); |
| } |
| |
| // current time is age after the last ntp cache; callers who |
| // want fresh values will hit makeAuthoritative() first. |
| return mCachedNtpTime + getCacheAge(); |
| } |
| } |