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      1 /*
      2  * Copyright (C) 2008 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.android.server.location;
     18 
     19 import android.text.TextUtils;
     20 import android.util.Log;
     21 
     22 import java.net.HttpURLConnection;
     23 import java.net.URL;
     24 import libcore.io.Streams;
     25 
     26 import java.io.IOException;
     27 import java.util.Properties;
     28 import java.util.Random;
     29 
     30 /**
     31  * A class for downloading GPS XTRA data.
     32  *
     33  * {@hide}
     34  */
     35 public class GpsXtraDownloader {
     36 
     37     private static final String TAG = "GpsXtraDownloader";
     38     private static final boolean DEBUG = Log.isLoggable(TAG, Log.DEBUG);
     39     private static final String DEFAULT_USER_AGENT = "Android";
     40 
     41     private final String[] mXtraServers;
     42     // to load balance our server requests
     43     private int mNextServerIndex;
     44     private final String mUserAgent;
     45 
     46     GpsXtraDownloader(Properties properties) {
     47         // read XTRA servers from the Properties object
     48         int count = 0;
     49         String server1 = properties.getProperty("XTRA_SERVER_1");
     50         String server2 = properties.getProperty("XTRA_SERVER_2");
     51         String server3 = properties.getProperty("XTRA_SERVER_3");
     52         if (server1 != null) count++;
     53         if (server2 != null) count++;
     54         if (server3 != null) count++;
     55 
     56         // Set User Agent from properties, if possible.
     57         String agent = properties.getProperty("XTRA_USER_AGENT");
     58         if (TextUtils.isEmpty(agent)) {
     59             mUserAgent = DEFAULT_USER_AGENT;
     60         } else {
     61             mUserAgent = agent;
     62         }
     63 
     64         if (count == 0) {
     65             Log.e(TAG, "No XTRA servers were specified in the GPS configuration");
     66             mXtraServers = null;
     67         } else {
     68             mXtraServers = new String[count];
     69             count = 0;
     70             if (server1 != null) mXtraServers[count++] = server1;
     71             if (server2 != null) mXtraServers[count++] = server2;
     72             if (server3 != null) mXtraServers[count++] = server3;
     73 
     74             // randomize first server
     75             Random random = new Random();
     76             mNextServerIndex = random.nextInt(count);
     77         }
     78     }
     79 
     80     byte[] downloadXtraData() {
     81         byte[] result = null;
     82         int startIndex = mNextServerIndex;
     83 
     84         if (mXtraServers == null) {
     85             return null;
     86         }
     87 
     88         // load balance our requests among the available servers
     89         while (result == null) {
     90             result = doDownload(mXtraServers[mNextServerIndex]);
     91 
     92             // increment mNextServerIndex and wrap around if necessary
     93             mNextServerIndex++;
     94             if (mNextServerIndex == mXtraServers.length) {
     95                 mNextServerIndex = 0;
     96             }
     97             // break if we have tried all the servers
     98             if (mNextServerIndex == startIndex) break;
     99         }
    100 
    101         return result;
    102     }
    103 
    104     protected byte[] doDownload(String url) {
    105         if (DEBUG) Log.d(TAG, "Downloading XTRA data from " + url);
    106 
    107         HttpURLConnection connection = null;
    108         try {
    109             connection = (HttpURLConnection) (new URL(url)).openConnection();
    110             connection.setRequestProperty(
    111                     "Accept",
    112                     "*/*, application/vnd.wap.mms-message, application/vnd.wap.sic");
    113             connection.setRequestProperty(
    114                     "x-wap-profile",
    115                     "http://www.openmobilealliance.org/tech/profiles/UAPROF/ccppschema-20021212#");
    116 
    117             connection.connect();
    118             int statusCode = connection.getResponseCode();
    119             if (statusCode != HttpURLConnection.HTTP_OK) {
    120                 if (DEBUG) Log.d(TAG, "HTTP error downloading gps XTRA: " + statusCode);
    121                 return null;
    122             }
    123 
    124             return Streams.readFully(connection.getInputStream());
    125         } catch (IOException ioe) {
    126             if (DEBUG) Log.d(TAG, "Error downloading gps XTRA: ", ioe);
    127         } finally {
    128             if (connection != null) {
    129                 connection.disconnect();
    130             }
    131         }
    132         return null;
    133     }
    134 
    135 }
    136