| /* |
| * Copyright (C) 2009 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 android.database.sqlite; |
| |
| import android.content.res.AssetFileDescriptor; |
| import android.database.Cursor; |
| import android.os.MemoryFile; |
| |
| import java.io.FileNotFoundException; |
| import java.io.IOException; |
| |
| /** |
| * Some helper functions for using SQLite database to implement content providers. |
| * |
| * @hide |
| */ |
| public class SQLiteContentHelper { |
| |
| /** |
| * Runs an SQLite query and returns an AssetFileDescriptor for the |
| * blob in column 0 of the first row. If the first column does |
| * not contain a blob, an unspecified exception is thrown. |
| * |
| * @param db Handle to a readable database. |
| * @param sql SQL query, possibly with query arguments. |
| * @param selectionArgs Query argument values, or {@code null} for no argument. |
| * @return If no exception is thrown, a non-null AssetFileDescriptor is returned. |
| * @throws FileNotFoundException If the query returns no results or the |
| * value of column 0 is NULL, or if there is an error creating the |
| * asset file descriptor. |
| */ |
| public static AssetFileDescriptor getBlobColumnAsAssetFile(SQLiteDatabase db, String sql, |
| String[] selectionArgs) throws FileNotFoundException { |
| try { |
| MemoryFile file = simpleQueryForBlobMemoryFile(db, sql, selectionArgs); |
| if (file == null) { |
| throw new FileNotFoundException("No results."); |
| } |
| return AssetFileDescriptor.fromMemoryFile(file); |
| } catch (IOException ex) { |
| throw new FileNotFoundException(ex.toString()); |
| } |
| } |
| |
| /** |
| * Runs an SQLite query and returns a MemoryFile for the |
| * blob in column 0 of the first row. If the first column does |
| * not contain a blob, an unspecified exception is thrown. |
| * |
| * @return A memory file, or {@code null} if the query returns no results |
| * or the value column 0 is NULL. |
| * @throws IOException If there is an error creating the memory file. |
| */ |
| // TODO: make this native and use the SQLite blob API to reduce copying |
| private static MemoryFile simpleQueryForBlobMemoryFile(SQLiteDatabase db, String sql, |
| String[] selectionArgs) throws IOException { |
| Cursor cursor = db.rawQuery(sql, selectionArgs); |
| if (cursor == null) { |
| return null; |
| } |
| try { |
| if (!cursor.moveToFirst()) { |
| return null; |
| } |
| byte[] bytes = cursor.getBlob(0); |
| if (bytes == null) { |
| return null; |
| } |
| MemoryFile file = new MemoryFile(null, bytes.length); |
| file.writeBytes(bytes, 0, 0, bytes.length); |
| file.deactivate(); |
| return file; |
| } finally { |
| cursor.close(); |
| } |
| } |
| |
| } |