CallbackDataSource.h revision da7e453e1d1c77959822cf9602ddfed1c50be445 
1/*
2 * Copyright 2015 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#ifndef ANDROID_CALLBACKDATASOURCE_H
18#define ANDROID_CALLBACKDATASOURCE_H
19
20#include <media/stagefright/DataSource.h>
21#include <media/stagefright/foundation/ADebug.h>
22
23namespace android {
24
25class IDataSource;
26class IMemory;
27
28// A stagefright DataSource that wraps a binder IDataSource. It's a "Callback"
29// DataSource because it calls back to the IDataSource for data.
30class CallbackDataSource : public DataSource {
31public:
32    CallbackDataSource(const sp<IDataSource>& iDataSource);
33    virtual ~CallbackDataSource();
34
35    // DataSource implementation.
36    virtual status_t initCheck() const;
37    virtual ssize_t readAt(off64_t offset, void *data, size_t size);
38    virtual status_t getSize(off64_t *size);
39
40private:
41    sp<IDataSource> mIDataSource;
42    sp<IMemory> mMemory;
43
44    DISALLOW_EVIL_CONSTRUCTORS(CallbackDataSource);
45};
46
47
48// A caching DataSource that wraps a CallbackDataSource. For reads smaller
49// than kCacheSize it will read up to kCacheSize ahead and cache it.
50// This reduces the number of binder round trips to the IDataSource and has a significant
51// impact on time taken for filetype sniffing and metadata extraction.
52class TinyCacheSource : public DataSource {
53public:
54    TinyCacheSource(const sp<DataSource>& source);
55
56    virtual status_t initCheck() const;
57    virtual ssize_t readAt(off64_t offset, void* data, size_t size);
58    virtual status_t getSize(off64_t* size);
59    virtual uint32_t flags();
60
61private:
62    // 2kb comes from experimenting with the time-to-first-frame from a MediaPlayer
63    // with an in-memory MediaDataSource source on a Nexus 5. Beyond 2kb there was
64    // no improvement.
65    enum {
66        kCacheSize = 2048,
67    };
68
69    sp<DataSource> mSource;
70    uint8_t mCache[kCacheSize];
71    off64_t mCachedOffset;
72    size_t mCachedSize;
73
74    DISALLOW_EVIL_CONSTRUCTORS(TinyCacheSource);
75};
76
77}; // namespace android
78
79#endif // ANDROID_CALLBACKDATASOURCE_H
80