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/*
* Copyright (C) 2008 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.location;
import android.net.TrafficStats;
import android.text.TextUtils;
import android.util.Log;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.Properties;
import java.util.Random;
import java.util.concurrent.TimeUnit;
/**
* A class for downloading GPS XTRA data.
*
* {@hide}
*/
public class GpsXtraDownloader {
private static final String TAG = "GpsXtraDownloader";
private static final boolean DEBUG = Log.isLoggable(TAG, Log.DEBUG);
private static final long MAXIMUM_CONTENT_LENGTH_BYTES = 1000000; // 1MB.
private static final String DEFAULT_USER_AGENT = "Android";
private static final int CONNECTION_TIMEOUT_MS = (int) TimeUnit.SECONDS.toMillis(30);
private final String[] mXtraServers;
// to load balance our server requests
private int mNextServerIndex;
private final String mUserAgent;
GpsXtraDownloader(Properties properties) {
// read XTRA servers from the Properties object
int count = 0;
String server1 = properties.getProperty("XTRA_SERVER_1");
String server2 = properties.getProperty("XTRA_SERVER_2");
String server3 = properties.getProperty("XTRA_SERVER_3");
if (server1 != null) count++;
if (server2 != null) count++;
if (server3 != null) count++;
// Set User Agent from properties, if possible.
String agent = properties.getProperty("XTRA_USER_AGENT");
if (TextUtils.isEmpty(agent)) {
mUserAgent = DEFAULT_USER_AGENT;
} else {
mUserAgent = agent;
}
if (count == 0) {
Log.e(TAG, "No XTRA servers were specified in the GPS configuration");
mXtraServers = null;
} else {
mXtraServers = new String[count];
count = 0;
if (server1 != null) mXtraServers[count++] = server1;
if (server2 != null) mXtraServers[count++] = server2;
if (server3 != null) mXtraServers[count++] = server3;
// randomize first server
Random random = new Random();
mNextServerIndex = random.nextInt(count);
}
}
byte[] downloadXtraData() {
byte[] result = null;
int startIndex = mNextServerIndex;
if (mXtraServers == null) {
return null;
}
// load balance our requests among the available servers
while (result == null) {
final int oldTag = TrafficStats.getAndSetThreadStatsTag(TrafficStats.TAG_SYSTEM_GPS);
try {
result = doDownload(mXtraServers[mNextServerIndex]);
} finally {
TrafficStats.setThreadStatsTag(oldTag);
}
// increment mNextServerIndex and wrap around if necessary
mNextServerIndex++;
if (mNextServerIndex == mXtraServers.length) {
mNextServerIndex = 0;
}
// break if we have tried all the servers
if (mNextServerIndex == startIndex) break;
}
return result;
}
protected byte[] doDownload(String url) {
if (DEBUG) Log.d(TAG, "Downloading XTRA data from " + url);
HttpURLConnection connection = null;
try {
connection = (HttpURLConnection) (new URL(url)).openConnection();
connection.setRequestProperty(
"Accept",
"*/*, application/vnd.wap.mms-message, application/vnd.wap.sic");
connection.setRequestProperty(
"x-wap-profile",
"http://www.openmobilealliance.org/tech/profiles/UAPROF/ccppschema-20021212#");
connection.setConnectTimeout(CONNECTION_TIMEOUT_MS);
connection.connect();
int statusCode = connection.getResponseCode();
if (statusCode != HttpURLConnection.HTTP_OK) {
if (DEBUG) Log.d(TAG, "HTTP error downloading gps XTRA: " + statusCode);
return null;
}
try (InputStream in = connection.getInputStream()) {
ByteArrayOutputStream bytes = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
int count;
while ((count = in.read(buffer)) != -1) {
bytes.write(buffer, 0, count);
if (bytes.size() > MAXIMUM_CONTENT_LENGTH_BYTES) {
if (DEBUG) Log.d(TAG, "XTRA file too large");
return null;
}
}
return bytes.toByteArray();
}
} catch (IOException ioe) {
if (DEBUG) Log.d(TAG, "Error downloading gps XTRA: ", ioe);
} finally {
if (connection != null) {
connection.disconnect();
}
}
return null;
}
}
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