Merge restored wifi APs, don't overwrite

We now preserve any already-known AP configuration information when
restoring wifi from backup, instead of flatly overwriting the known
definitions with the historical ones.  This means that if you are
performing setup while connected to an AP unknown in the restored
dataset, you will retain your connection instead of seeing it drop
partway through the restore process because suddenly the supplicant
"forgot" how to connect to it.

Duplicates are resolved by retaining the currently-defined network
configuration and discarding the historical one.

Bug 6443790

Change-Id: I1f44cc6a01fc4ae7c4b680682a10fcb7a0be65dc

Author: Christopher Tate

packages/SettingsProvider/src/com/android/providers/settings/SettingsBackupAgent.java

@@ -34,6 +34,7 @@
 import java.io.BufferedOutputStream;
 import java.io.BufferedReader;
 import java.io.BufferedWriter;
+import java.io.CharArrayReader;
 import java.io.DataInputStream;
 import java.io.DataOutputStream;
 import java.io.EOFException;
@@ -45,7 +46,11 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
+import java.io.Reader;
+import java.io.Writer;
+import java.util.ArrayList;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.Map;
 import java.util.zip.CRC32;
 
@@ -55,7 +60,7 @@
  */
 public class SettingsBackupAgent extends BackupAgentHelper {
     private static final boolean DEBUG = false;
-    private static final boolean DEBUG_BACKUP = DEBUG || true;
+    private static final boolean DEBUG_BACKUP = DEBUG || false;
 
     private static final String KEY_SYSTEM = "system";
     private static final String KEY_SECURE = "secure";
@@ -111,6 +116,130 @@ public class SettingsBackupAgent extends BackupAgentHelper {
     private WifiManager mWfm;
     private static String mWifiConfigFile;
 
+    // Class for capturing a network definition from the wifi supplicant config file
+    static class Network {
+        String ssid = "";  // equals() and hashCode() need these to be non-null
+        String key_mgmt = "";
+        final ArrayList<String> rawLines = new ArrayList<String>();
+
+        public static Network readFromStream(BufferedReader in) {
+            final Network n = new Network();
+            String line;
+            try {
+                while (in.ready()) {
+                    line = in.readLine();
+                    if (line == null || line.startsWith("}")) {
+                        break;
+                    }
+                    n.rememberLine(line);
+                }
+            } catch (IOException e) {
+                return null;
+            }
+            return n;
+        }
+
+        void rememberLine(String line) {
+            // can't rely on particular whitespace patterns so strip leading/trailing
+            line = line.trim();
+            if (line.isEmpty()) return; // only whitespace; drop the line
+            rawLines.add(line);
+
+            // remember the ssid and key_mgmt lines for duplicate culling
+            if (line.startsWith("ssid")) {
+                ssid = line;
+            } else if (line.startsWith("key_mgmt")) {
+                key_mgmt = line;
+            }
+        }
+
+        public void write(Writer w) throws IOException {
+            w.write("\nnetwork={\n");
+            for (String line : rawLines) {
+                w.write("\t" + line + "\n");
+            }
+            w.write("}\n");
+        }
+
+        public void dump() {
+            Log.v(TAG, "network={");
+            for (String line : rawLines) {
+                Log.v(TAG, "   " + line);
+            }
+            Log.v(TAG, "}");
+        }
+
+        // Same approach as Pair.equals() and Pair.hashCode()
+        @Override
+        public boolean equals(Object o) {
+            if (o == this) return true;
+            if (!(o instanceof Network)) return false;
+            final Network other;
+            try {
+                other = (Network) o;
+            } catch (ClassCastException e) {
+                return false;
+            }
+            return ssid.equals(other.ssid) && key_mgmt.equals(other.key_mgmt);
+        }
+
+        @Override
+        public int hashCode() {
+            int result = 17;
+            result = 31 * result + ssid.hashCode();
+            result = 31 * result + key_mgmt.hashCode();
+            return result;
+        }
+    }
+
+    // Ingest multiple wifi config file fragments, looking for network={} blocks
+    // and eliminating duplicates
+    class WifiNetworkSettings {
+        // One for fast lookup, one for maintaining ordering
+        final HashSet<Network> mKnownNetworks = new HashSet<Network>();
+        final ArrayList<Network> mNetworks = new ArrayList<Network>(8);
+
+        public void readNetworks(BufferedReader in) {
+            try {
+                String line;
+                while (in.ready()) {
+                    line = in.readLine();
+                    if (line != null) {
+                        // Parse out 'network=' decls so we can ignore duplicates
+                        if (line.startsWith("network")) {
+                            Network net = Network.readFromStream(in);
+                            if (! mKnownNetworks.contains(net)) {
+                                if (DEBUG_BACKUP) {
+                                    Log.v(TAG, "Adding " + net.ssid + " / " + net.key_mgmt);
+                                }
+                                mKnownNetworks.add(net);
+                                mNetworks.add(net);
+                            } else {
+                                if (DEBUG_BACKUP) {
+                                    Log.v(TAG, "Dupe; skipped " + net.ssid + " / " + net.key_mgmt);
+                                }
+                            }
+                        }
+                    }
+                }
+            } catch (IOException e) {
+                // whatever happened, we're done now
+            }
+        }
+
+        public void write(Writer w) throws IOException {
+            for (Network net : mNetworks) {
+                net.write(w);
+            }
+        }
+
+        public void dump() {
+            for (Network net : mNetworks) {
+                net.dump();
+            }
+        }
+    }
+
     @Override
     public void onCreate() {
         if (DEBUG_BACKUP) Log.d(TAG, "onCreate() invoked");
@@ -622,29 +751,51 @@ private void restoreWifiSupplicant(String filename, BackupDataInput data) {
 
     private void restoreWifiSupplicant(String filename, byte[] bytes, int size) {
         try {
+            WifiNetworkSettings supplicantImage = new WifiNetworkSettings();
+
             File supplicantFile = new File(FILE_WIFI_SUPPLICANT);
-            if (supplicantFile.exists()) supplicantFile.delete();
-            copyWifiSupplicantTemplate();
+            if (supplicantFile.exists()) {
+                // Retain the existing APs; we'll append the restored ones to them
+                BufferedReader in = new BufferedReader(new FileReader(FILE_WIFI_SUPPLICANT));
+                supplicantImage.readNetworks(in);
+                in.close();
 
-            OutputStream os = new BufferedOutputStream(new FileOutputStream(filename, true));
-            os.write("\n".getBytes());
-            os.write(bytes, 0, size);
-            os.close();
+                supplicantFile.delete();
+            }
+
+            // Incorporate the restore AP information
+            if (size > 0) {
+                char[] restoredAsBytes = new char[size];
+                for (int i = 0; i < size; i++) restoredAsBytes[i] = (char) bytes[i];
+                BufferedReader in = new BufferedReader(new CharArrayReader(restoredAsBytes));
+                supplicantImage.readNetworks(in);
+
+                if (DEBUG_BACKUP) {
+                    Log.v(TAG, "Final AP list:");
+                    supplicantImage.dump();
+                }
+            }
+
+            // Install the correct default template
+            BufferedWriter bw = new BufferedWriter(new FileWriter(FILE_WIFI_SUPPLICANT));
+            copyWifiSupplicantTemplate(bw);
+
+            // Write the restored supplicant config and we're done
+            supplicantImage.write(bw);
+            bw.close();
         } catch (IOException ioe) {
             Log.w(TAG, "Couldn't restore " + filename);
         }
     }
 
-    private void copyWifiSupplicantTemplate() {
+    private void copyWifiSupplicantTemplate(BufferedWriter bw) {
         try {
             BufferedReader br = new BufferedReader(new FileReader(FILE_WIFI_SUPPLICANT_TEMPLATE));
-            BufferedWriter bw = new BufferedWriter(new FileWriter(FILE_WIFI_SUPPLICANT));
             char[] temp = new char[1024];
             int size;
             while ((size = br.read(temp)) > 0) {
                 bw.write(temp, 0, size);
             }
-            bw.close();
             br.close();
         } catch (IOException ioe) {
             Log.w(TAG, "Couldn't copy wpa_supplicant file");