1 /* 2 * Copyright (C) 2009 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 android.database.sqlite; 18 19 import android.content.res.AssetFileDescriptor; 20 import android.database.Cursor; 21 import android.os.MemoryFile; 22 23 import java.io.FileNotFoundException; 24 import java.io.IOException; 25 26 /** 27 * Some helper functions for using SQLite database to implement content providers. 28 * 29 * @hide 30 */ 31 public class SQLiteContentHelper { 32 33 /** 34 * Runs an SQLite query and returns an AssetFileDescriptor for the 35 * blob in column 0 of the first row. If the first column does 36 * not contain a blob, an unspecified exception is thrown. 37 * 38 * @param db Handle to a readable database. 39 * @param sql SQL query, possibly with query arguments. 40 * @param selectionArgs Query argument values, or {@code null} for no argument. 41 * @return If no exception is thrown, a non-null AssetFileDescriptor is returned. 42 * @throws FileNotFoundException If the query returns no results or the 43 * value of column 0 is NULL, or if there is an error creating the 44 * asset file descriptor. 45 */ getBlobColumnAsAssetFile(SQLiteDatabase db, String sql, String[] selectionArgs)46 public static AssetFileDescriptor getBlobColumnAsAssetFile(SQLiteDatabase db, String sql, 47 String[] selectionArgs) throws FileNotFoundException { 48 try { 49 MemoryFile file = simpleQueryForBlobMemoryFile(db, sql, selectionArgs); 50 if (file == null) { 51 throw new FileNotFoundException("No results."); 52 } 53 return AssetFileDescriptor.fromMemoryFile(file); 54 } catch (IOException ex) { 55 throw new FileNotFoundException(ex.toString()); 56 } 57 } 58 59 /** 60 * Runs an SQLite query and returns a MemoryFile for the 61 * blob in column 0 of the first row. If the first column does 62 * not contain a blob, an unspecified exception is thrown. 63 * 64 * @return A memory file, or {@code null} if the query returns no results 65 * or the value column 0 is NULL. 66 * @throws IOException If there is an error creating the memory file. 67 */ 68 // TODO: make this native and use the SQLite blob API to reduce copying simpleQueryForBlobMemoryFile(SQLiteDatabase db, String sql, String[] selectionArgs)69 private static MemoryFile simpleQueryForBlobMemoryFile(SQLiteDatabase db, String sql, 70 String[] selectionArgs) throws IOException { 71 Cursor cursor = db.rawQuery(sql, selectionArgs); 72 if (cursor == null) { 73 return null; 74 } 75 try { 76 if (!cursor.moveToFirst()) { 77 return null; 78 } 79 byte[] bytes = cursor.getBlob(0); 80 if (bytes == null) { 81 return null; 82 } 83 MemoryFile file = new MemoryFile(null, bytes.length); 84 file.writeBytes(bytes, 0, 0, bytes.length); 85 file.deactivate(); 86 return file; 87 } finally { 88 cursor.close(); 89 } 90 } 91 92 } 93