1 /*
2  * Copyright (C) 2011 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 com.android.ide.eclipse.gltrace;
18 
19 import com.android.ide.eclipse.gltrace.GLProtoBuf.GLMessage;
20 import com.google.protobuf.InvalidProtocolBufferException;
21 
22 import java.io.EOFException;
23 import java.io.IOException;
24 import java.io.RandomAccessFile;
25 
26 public class TraceFileReader {
27     /** Maximum size for a protocol buffer message.
28      * The message size is dominated by the size of the compressed framebuffer.
29      * Currently, we assume that the maximum is for a 1080p display. Since the buffers compress
30      * well, we should probably never get close to this.
31      */
32     private static final int MAX_PROTOBUF_SIZE = 1920 * 1080 * 100;
33 
34     /**
35      * Obtain the next protobuf message in this file.
36      * @param file file to read from
37      * @param offset offset to start reading from
38      * @return protobuf message at given offset
39      * @throws IOException in case of file I/O errors
40      * @throws InvalidProtocolBufferException if protobuf is not well formed
41      */
getMessageAtOffset(RandomAccessFile file, long offset)42     public GLMessage getMessageAtOffset(RandomAccessFile file, long offset) throws IOException {
43         int len;
44         byte[] b;
45         try {
46             if (offset != -1) {
47                 file.seek(offset);
48             }
49 
50             len = file.readInt();
51             if (len > MAX_PROTOBUF_SIZE) {
52                 String msg = String.format(
53                         "Unexpectedly large (%d bytes) protocol buffer message encountered.",
54                         len);
55                 throw new InvalidProtocolBufferException(msg);
56             }
57 
58             b = new byte[len];
59             file.readFully(b);
60         } catch (EOFException e) {
61             return null;
62         }
63 
64         return GLMessage.parseFrom(b);
65     }
66 }
67