1 /*
2  * Copyright (C) 2012 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 
18 package android.media;
19 
20 import java.io.Closeable;
21 import java.io.IOException;
22 
23 /**
24  * For supplying media data to the framework. Implement this if your app has
25  * special requirements for the way media data is obtained.
26  *
27  * <p class="note">Methods of this interface may be called on multiple different
28  * threads. There will be a thread synchronization point between each call to ensure that
29  * modifications to the state of your MediaDataSource are visible to future calls. This means
30  * you don't need to do your own synchronization unless you're modifying the
31  * MediaDataSource from another thread while it's being used by the framework.</p>
32  */
33 public abstract class MediaDataSource implements Closeable {
34     /**
35      * Called to request data from the given position.
36      *
37      * Implementations should should write up to {@code size} bytes into
38      * {@code buffer}, and return the number of bytes written.
39      *
40      * Return {@code 0} if size is zero (thus no bytes are read).
41      *
42      * Return {@code -1} to indicate that end of stream is reached.
43      *
44      * @param position the position in the data source to read from.
45      * @param buffer the buffer to read the data into.
46      * @param offset the offset within buffer to read the data into.
47      * @param size the number of bytes to read.
48      * @throws IOException on fatal errors.
49      * @return the number of bytes read, or -1 if there was an error.
50      */
readAt(long position, byte[] buffer, int offset, int size)51     public abstract int readAt(long position, byte[] buffer, int offset, int size)
52             throws IOException;
53 
54     /**
55      * Called to get the size of the data source.
56      *
57      * @throws IOException on fatal errors
58      * @return the size of data source in bytes, or -1 if the size is unknown.
59      */
getSize()60     public abstract long getSize() throws IOException;
61 }
62