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
17package com.android.server.location;
18
19import android.text.TextUtils;
20import android.util.Log;
21
22import java.io.IOException;
23import java.net.HttpURLConnection;
24import java.net.URL;
25
26import java.io.ByteArrayOutputStream;
27import java.io.InputStream;
28import java.io.IOException;
29import java.util.Properties;
30import java.util.Random;
31import java.util.concurrent.TimeUnit;
32
33import libcore.io.Streams;
34
35/**
36 * A class for downloading GPS XTRA data.
37 *
38 * {@hide}
39 */
40public class GpsXtraDownloader {
41
42    private static final String TAG = "GpsXtraDownloader";
43    private static final boolean DEBUG = Log.isLoggable(TAG, Log.DEBUG);
44    private static final long MAXIMUM_CONTENT_LENGTH_BYTES = 1000000;  // 1MB.
45    private static final String DEFAULT_USER_AGENT = "Android";
46    private static final int CONNECTION_TIMEOUT_MS = (int) TimeUnit.SECONDS.toMillis(30);
47
48    private final String[] mXtraServers;
49    // to load balance our server requests
50    private int mNextServerIndex;
51    private final String mUserAgent;
52
53    GpsXtraDownloader(Properties properties) {
54        // read XTRA servers from the Properties object
55        int count = 0;
56        String server1 = properties.getProperty("XTRA_SERVER_1");
57        String server2 = properties.getProperty("XTRA_SERVER_2");
58        String server3 = properties.getProperty("XTRA_SERVER_3");
59        if (server1 != null) count++;
60        if (server2 != null) count++;
61        if (server3 != null) count++;
62
63        // Set User Agent from properties, if possible.
64        String agent = properties.getProperty("XTRA_USER_AGENT");
65        if (TextUtils.isEmpty(agent)) {
66            mUserAgent = DEFAULT_USER_AGENT;
67        } else {
68            mUserAgent = agent;
69        }
70
71        if (count == 0) {
72            Log.e(TAG, "No XTRA servers were specified in the GPS configuration");
73            mXtraServers = null;
74        } else {
75            mXtraServers = new String[count];
76            count = 0;
77            if (server1 != null) mXtraServers[count++] = server1;
78            if (server2 != null) mXtraServers[count++] = server2;
79            if (server3 != null) mXtraServers[count++] = server3;
80
81            // randomize first server
82            Random random = new Random();
83            mNextServerIndex = random.nextInt(count);
84        }
85    }
86
87    byte[] downloadXtraData() {
88        byte[] result = null;
89        int startIndex = mNextServerIndex;
90
91        if (mXtraServers == null) {
92            return null;
93        }
94
95        // load balance our requests among the available servers
96        while (result == null) {
97            result = doDownload(mXtraServers[mNextServerIndex]);
98
99            // increment mNextServerIndex and wrap around if necessary
100            mNextServerIndex++;
101            if (mNextServerIndex == mXtraServers.length) {
102                mNextServerIndex = 0;
103            }
104            // break if we have tried all the servers
105            if (mNextServerIndex == startIndex) break;
106        }
107
108        return result;
109    }
110
111    protected byte[] doDownload(String url) {
112        if (DEBUG) Log.d(TAG, "Downloading XTRA data from " + url);
113
114        HttpURLConnection connection = null;
115        try {
116            connection = (HttpURLConnection) (new URL(url)).openConnection();
117            connection.setRequestProperty(
118                    "Accept",
119                    "*/*, application/vnd.wap.mms-message, application/vnd.wap.sic");
120            connection.setRequestProperty(
121                    "x-wap-profile",
122                    "http://www.openmobilealliance.org/tech/profiles/UAPROF/ccppschema-20021212#");
123            connection.setConnectTimeout(CONNECTION_TIMEOUT_MS);
124
125            connection.connect();
126            int statusCode = connection.getResponseCode();
127            if (statusCode != HttpURLConnection.HTTP_OK) {
128                if (DEBUG) Log.d(TAG, "HTTP error downloading gps XTRA: " + statusCode);
129                return null;
130            }
131
132            try (InputStream in = connection.getInputStream()) {
133                ByteArrayOutputStream bytes = new ByteArrayOutputStream();
134                byte[] buffer = new byte[1024];
135                int count;
136                while ((count = in.read(buffer)) != -1) {
137                    bytes.write(buffer, 0, count);
138                    if (bytes.size() > MAXIMUM_CONTENT_LENGTH_BYTES) {
139                        if (DEBUG) Log.d(TAG, "XTRA file too large");
140                        return null;
141                    }
142                }
143                return bytes.toByteArray();
144            }
145        } catch (IOException ioe) {
146            if (DEBUG) Log.d(TAG, "Error downloading gps XTRA: ", ioe);
147        } finally {
148            if (connection != null) {
149                connection.disconnect();
150            }
151        }
152        return null;
153    }
154
155}
156
157