SntpClient.java revision 499a121c13672294fd691aea190b4d4560768665
19066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project/* 29066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * Copyright (C) 2008 The Android Open Source Project 39066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * 49066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * Licensed under the Apache License, Version 2.0 (the "License"); 59066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * you may not use this file except in compliance with the License. 69066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * You may obtain a copy of the License at 79066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * 89066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * http://www.apache.org/licenses/LICENSE-2.0 99066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * 109066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * Unless required by applicable law or agreed to in writing, software 119066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * distributed under the License is distributed on an "AS IS" BASIS, 129066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 139066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * See the License for the specific language governing permissions and 149066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * limitations under the License. 159066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project */ 169066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project 179066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Projectpackage android.net; 189066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project 199066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Projectimport android.os.SystemClock; 209066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Projectimport android.util.Config; 219066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Projectimport android.util.Log; 229066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project 239066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Projectimport java.io.IOException; 249066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Projectimport java.net.DatagramPacket; 259066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Projectimport java.net.DatagramSocket; 269066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Projectimport java.net.InetAddress; 279066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project 289066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project/** 299066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * {@hide} 309066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * 319066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * Simple SNTP client class for retrieving network time. 329066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * 339066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * Sample usage: 349066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * <pre>SntpClient client = new SntpClient(); 359066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * if (client.requestTime("time.foo.com")) { 369066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * long now = client.getNtpTime() + SystemClock.elapsedRealtime() - client.getNtpTimeReference(); 379066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * } 389066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * </pre> 399066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project */ 409066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Projectpublic class SntpClient 419066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project{ 429066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project private static final String TAG = "SntpClient"; 439066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project 449066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project private static final int REFERENCE_TIME_OFFSET = 16; 459066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project private static final int ORIGINATE_TIME_OFFSET = 24; 469066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project private static final int RECEIVE_TIME_OFFSET = 32; 479066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project private static final int TRANSMIT_TIME_OFFSET = 40; 489066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project private static final int NTP_PACKET_SIZE = 48; 499066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project 509066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project private static final int NTP_PORT = 123; 519066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project private static final int NTP_MODE_CLIENT = 3; 529066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project private static final int NTP_VERSION = 3; 539066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project 549066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project // Number of seconds between Jan 1, 1900 and Jan 1, 1970 559066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project // 70 years plus 17 leap days 569066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project private static final long OFFSET_1900_TO_1970 = ((365L * 70L) + 17L) * 24L * 60L * 60L; 579066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project 589066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project // system time computed from NTP server response 599066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project private long mNtpTime; 609066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project 619066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project // value of SystemClock.elapsedRealtime() corresponding to mNtpTime 629066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project private long mNtpTimeReference; 639066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project 649066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project // round trip time in milliseconds 659066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project private long mRoundTripTime; 669066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project 679066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project /** 689066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * Sends an SNTP request to the given host and processes the response. 699066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * 709066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * @param host host name of the server. 719066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * @param timeout network timeout in milliseconds. 729066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * @return true if the transaction was successful. 739066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project */ 749066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project public boolean requestTime(String host, int timeout) { 759066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project try { 769066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project DatagramSocket socket = new DatagramSocket(); 779066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project socket.setSoTimeout(timeout); 789066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project InetAddress address = InetAddress.getByName(host); 799066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project byte[] buffer = new byte[NTP_PACKET_SIZE]; 809066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project DatagramPacket request = new DatagramPacket(buffer, buffer.length, address, NTP_PORT); 819066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project 829066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project // set mode = 3 (client) and version = 3 839066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project // mode is in low 3 bits of first byte 849066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project // version is in bits 3-5 of first byte 859066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project buffer[0] = NTP_MODE_CLIENT | (NTP_VERSION << 3); 869066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project 879066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project // get current time and write it to the request packet 889066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project long requestTime = System.currentTimeMillis(); 899066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project long requestTicks = SystemClock.elapsedRealtime(); 909066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project writeTimeStamp(buffer, TRANSMIT_TIME_OFFSET, requestTime); 919066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project 929066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project socket.send(request); 939066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project 949066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project // read the response 959066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project DatagramPacket response = new DatagramPacket(buffer, buffer.length); 969066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project socket.receive(response); 979066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project long responseTicks = SystemClock.elapsedRealtime(); 989066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project long responseTime = requestTime + (responseTicks - requestTicks); 999066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project socket.close(); 1009066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project 1019066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project // extract the results 1029066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project long originateTime = readTimeStamp(buffer, ORIGINATE_TIME_OFFSET); 1039066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project long receiveTime = readTimeStamp(buffer, RECEIVE_TIME_OFFSET); 1049066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project long transmitTime = readTimeStamp(buffer, TRANSMIT_TIME_OFFSET); 1059066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project long roundTripTime = responseTicks - requestTicks - (transmitTime - receiveTime); 106499a121c13672294fd691aea190b4d4560768665Robert Greenwalt // receiveTime = originateTime + transit + skew 107499a121c13672294fd691aea190b4d4560768665Robert Greenwalt // responseTime = transmitTime + transit - skew 108499a121c13672294fd691aea190b4d4560768665Robert Greenwalt // clockOffset = ((receiveTime - originateTime) + (transmitTime - responseTime))/2 109499a121c13672294fd691aea190b4d4560768665Robert Greenwalt // = ((originateTime + transit + skew - originateTime) + 110499a121c13672294fd691aea190b4d4560768665Robert Greenwalt // (transmitTime - (transmitTime + transit - skew)))/2 111499a121c13672294fd691aea190b4d4560768665Robert Greenwalt // = ((transit + skew) + (transmitTime - transmitTime - transit + skew))/2 112499a121c13672294fd691aea190b4d4560768665Robert Greenwalt // = (transit + skew - transit + skew)/2 113499a121c13672294fd691aea190b4d4560768665Robert Greenwalt // = (2 * skew)/2 = skew 114499a121c13672294fd691aea190b4d4560768665Robert Greenwalt long clockOffset = ((receiveTime - originateTime) + (transmitTime - responseTime))/2; 1159066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project if (Config.LOGD) Log.d(TAG, "round trip: " + roundTripTime + " ms"); 1169066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project if (Config.LOGD) Log.d(TAG, "clock offset: " + clockOffset + " ms"); 1179066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project 118499a121c13672294fd691aea190b4d4560768665Robert Greenwalt // save our results - use the times on this side of the network latency 119499a121c13672294fd691aea190b4d4560768665Robert Greenwalt // (response rather than request time) 120499a121c13672294fd691aea190b4d4560768665Robert Greenwalt mNtpTime = responseTime + clockOffset; 121499a121c13672294fd691aea190b4d4560768665Robert Greenwalt mNtpTimeReference = responseTicks; 1229066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project mRoundTripTime = roundTripTime; 1239066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project } catch (Exception e) { 1249066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project if (Config.LOGD) Log.d(TAG, "request time failed: " + e); 1259066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project return false; 1269066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project } 1279066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project 1289066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project return true; 1299066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project } 1309066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project 1319066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project /** 1329066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * Returns the time computed from the NTP transaction. 1339066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * 1349066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * @return time value computed from NTP server response. 1359066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project */ 1369066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project public long getNtpTime() { 1379066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project return mNtpTime; 1389066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project } 1399066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project 1409066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project /** 1419066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * Returns the reference clock value (value of SystemClock.elapsedRealtime()) 1429066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * corresponding to the NTP time. 1439066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * 1449066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * @return reference clock corresponding to the NTP time. 1459066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project */ 1469066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project public long getNtpTimeReference() { 1479066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project return mNtpTimeReference; 1489066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project } 1499066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project 1509066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project /** 1519066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * Returns the round trip time of the NTP transaction 1529066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * 1539066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * @return round trip time in milliseconds. 1549066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project */ 1559066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project public long getRoundTripTime() { 1569066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project return mRoundTripTime; 1579066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project } 1589066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project 1599066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project /** 1609066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * Reads an unsigned 32 bit big endian number from the given offset in the buffer. 1619066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project */ 1629066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project private long read32(byte[] buffer, int offset) { 1639066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project byte b0 = buffer[offset]; 1649066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project byte b1 = buffer[offset+1]; 1659066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project byte b2 = buffer[offset+2]; 1669066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project byte b3 = buffer[offset+3]; 1679066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project 1689066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project // convert signed bytes to unsigned values 1699066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project int i0 = ((b0 & 0x80) == 0x80 ? (b0 & 0x7F) + 0x80 : b0); 1709066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project int i1 = ((b1 & 0x80) == 0x80 ? (b1 & 0x7F) + 0x80 : b1); 1719066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project int i2 = ((b2 & 0x80) == 0x80 ? (b2 & 0x7F) + 0x80 : b2); 1729066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project int i3 = ((b3 & 0x80) == 0x80 ? (b3 & 0x7F) + 0x80 : b3); 1739066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project 1749066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project return ((long)i0 << 24) + ((long)i1 << 16) + ((long)i2 << 8) + (long)i3; 1759066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project } 1769066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project 1779066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project /** 1789066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * Reads the NTP time stamp at the given offset in the buffer and returns 1799066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * it as a system time (milliseconds since January 1, 1970). 1809066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project */ 1819066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project private long readTimeStamp(byte[] buffer, int offset) { 1829066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project long seconds = read32(buffer, offset); 1839066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project long fraction = read32(buffer, offset + 4); 1849066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project return ((seconds - OFFSET_1900_TO_1970) * 1000) + ((fraction * 1000L) / 0x100000000L); 1859066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project } 1869066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project 1879066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project /** 1889066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * Writes system time (milliseconds since January 1, 1970) as an NTP time stamp 1899066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project * at the given offset in the buffer. 1909066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project */ 1919066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project private void writeTimeStamp(byte[] buffer, int offset, long time) { 1929066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project long seconds = time / 1000L; 1939066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project long milliseconds = time - seconds * 1000L; 1949066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project seconds += OFFSET_1900_TO_1970; 1959066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project 1969066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project // write seconds in big endian format 1979066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project buffer[offset++] = (byte)(seconds >> 24); 1989066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project buffer[offset++] = (byte)(seconds >> 16); 1999066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project buffer[offset++] = (byte)(seconds >> 8); 2009066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project buffer[offset++] = (byte)(seconds >> 0); 2019066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project 2029066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project long fraction = milliseconds * 0x100000000L / 1000L; 2039066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project // write fraction in big endian format 2049066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project buffer[offset++] = (byte)(fraction >> 24); 2059066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project buffer[offset++] = (byte)(fraction >> 16); 2069066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project buffer[offset++] = (byte)(fraction >> 8); 2079066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project // low order bits should be random data 2089066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project buffer[offset++] = (byte)(Math.random() * 255.0); 2099066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project } 2109066cfe9886ac131c34d59ed0e2d287b0e3c0087The Android Open Source Project} 211