Add "call" method on ContentProvider.

This permits implementing interfaces which are faster than using
remote Cursors.  It then uses it for Settings & SettingProvider, which
together account for ~50% of total ContentProvider event loop stalls
across Froyo dogfooders.

For fetching Settings this looks like it should reduce average
Settings lookup from 10 ms to 0.4 ms on Sholes, once the
SettingsProvider serves most gets from in-memory cache.  Currently it
brings the Sholes average down from 10ms to 2.5 ms while still using
SQLite queries on each get.

1 files changed, 42 insertions, 0 deletions

diff --git a/packages/SettingsProvider/src/com/android/providers/settings/SettingsProvider.java b/packages/SettingsProvider/src/com/android/providers/settings/SettingsProvider.java
index db802d3..4f1146b 100644
--- a/packages/SettingsProvider/src/com/android/providers/settings/SettingsProvider.java
+++ b/packages/SettingsProvider/src/com/android/providers/settings/SettingsProvider.java
@@ -30,9 +30,11 @@ import android.content.pm.PackageManager;
 import android.content.res.AssetFileDescriptor;
 import android.database.Cursor;
 import android.database.sqlite.SQLiteDatabase;
+import android.database.sqlite.SQLiteException;
 import android.database.sqlite.SQLiteQueryBuilder;
 import android.media.RingtoneManager;
 import android.net.Uri;
+import android.os.Bundle;
 import android.os.ParcelFileDescriptor;
 import android.os.SystemProperties;
 import android.provider.DrmStore;
@@ -48,6 +50,8 @@ public class SettingsProvider extends ContentProvider {
     private static final String TABLE_FAVORITES = "favorites";
     private static final String TABLE_OLD_FAVORITES = "old_favorites";
 
+    private static final String[] COLUMN_VALUE = new String[] { "value" };
+
     protected DatabaseHelper mOpenHelper;
     private BackupManager mBackupManager;
 
@@ -220,6 +224,44 @@ public class SettingsProvider extends ContentProvider {
         }
     }
 
+    /**
+     * Fast path that avoids the use of chatty remoted Cursors.
+     */
+    @Override
+    public Bundle call(String method, String request, Bundle args) {
+        if (Settings.CALL_METHOD_GET_SYSTEM.equals(method)) {
+            return lookupValue("system", request);
+        }
+
+        if (Settings.CALL_METHOD_GET_SECURE.equals(method)) {
+            return lookupValue("secure", request);
+        }
+        return null;
+    }
+
+    // Looks up value 'key' in 'table' and returns either a single-pair Bundle,
+    // possibly with a null value, or null on failure.
+    private Bundle lookupValue(String table, String key) {
+        // TODO: avoid database lookup and serve from in-process cache.
+        SQLiteDatabase db = mOpenHelper.getReadableDatabase();
+        Cursor cursor = null;
+        try {
+            cursor = db.query(table, COLUMN_VALUE, "name=?", new String[]{key},
+                              null, null, null, null);
+            if (cursor != null && cursor.getCount() == 1) {
+                cursor.moveToFirst();
+                String value = cursor.getString(0);
+                return Bundle.forPair("value", value);
+            }
+        } catch (SQLiteException e) {
+            Log.w(TAG, "settings lookup error", e);
+            return null;
+        } finally {
+            if (cursor != null) cursor.close();
+        }
+        return Bundle.forPair("value", null);
+    }
+
     @Override
     public Cursor query(Uri url, String[] select, String where, String[] whereArgs, String sort) {
         SqlArguments args = new SqlArguments(url, where, whereArgs);