Metadata.cpp revision 29357bc2c0dd7c43ad3bd0c8e3efa4e6fd9bfd47 
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//#define LOG_NDEBUG 0
18#define LOG_TAG "Metadata"
19#include <utils/Log.h>
20
21#include <sys/types.h>
22#include <media/Metadata.h>
23#include <binder/Parcel.h>
24#include <utils/Errors.h>
25#include <utils/RefBase.h>
26
27// This file contains code to serialize Metadata triples (key, type,
28// value) into a parcel. The Parcel is destinated to be decoded by the
29// Metadata.java class.
30
31namespace {
32// All these constants below must be kept in sync with Metadata.java.
33enum MetadataId {
34    FIRST_SYSTEM_ID = 1,
35    LAST_SYSTEM_ID = 31,
36    FIRST_CUSTOM_ID = 8192
37};
38
39// Types
40enum Types {
41    STRING_VAL = 1,
42    INTEGER_VAL,
43    BOOLEAN_VAL,
44    LONG_VAL,
45    DOUBLE_VAL,
46    DATE_VAL,
47    BYTE_ARRAY_VAL,
48};
49
50const size_t kRecordHeaderSize = 3 * sizeof(int32_t);
51const int32_t kMetaMarker = 0x4d455441;  // 'M' 'E' 'T' 'A'
52
53}  // anonymous namespace
54
55namespace android {
56namespace media {
57
58Metadata::Metadata(Parcel *p)
59    :mData(p),
60     mBegin(p->dataPosition()) { }
61
62Metadata::~Metadata() { }
63
64void Metadata::resetParcel()
65{
66    mData->setDataPosition(mBegin);
67}
68
69// Update the 4 bytes int at the beginning of the parcel which holds
70// the number of bytes written so far.
71void Metadata::updateLength()
72{
73    const size_t end = mData->dataPosition();
74
75    mData->setDataPosition(mBegin);
76    mData->writeInt32(end - mBegin);
77    mData->setDataPosition(end);
78}
79
80// Write the header. The java layer will look for the marker.
81bool Metadata::appendHeader()
82{
83    bool ok = true;
84
85    // Placeholder for the length of the metadata
86    ok = ok && mData->writeInt32(-1) == OK;
87    ok = ok && mData->writeInt32(kMetaMarker) == OK;
88    return ok;
89}
90
91bool Metadata::appendBool(int key, bool val)
92{
93    if (!checkKey(key)) {
94        return false;
95    }
96
97    const size_t begin = mData->dataPosition();
98    bool ok = true;
99
100    // 4 int32s: size, key, type, value.
101    ok = ok && mData->writeInt32(4 * sizeof(int32_t)) == OK;
102    ok = ok && mData->writeInt32(key) == OK;
103    ok = ok && mData->writeInt32(BOOLEAN_VAL) == OK;
104    ok = ok && mData->writeInt32(val ? 1 : 0) == OK;
105    if (!ok) {
106        mData->setDataPosition(begin);
107    }
108    return ok;
109}
110
111bool Metadata::appendInt32(int key, int32_t val)
112{
113    if (!checkKey(key)) {
114        return false;
115    }
116
117    const size_t begin = mData->dataPosition();
118    bool ok = true;
119
120    // 4 int32s: size, key, type, value.
121    ok = ok && mData->writeInt32(4 * sizeof(int32_t)) == OK;
122    ok = ok && mData->writeInt32(key) == OK;
123    ok = ok && mData->writeInt32(INTEGER_VAL) == OK;
124    ok = ok && mData->writeInt32(val) == OK;
125    if (!ok) {
126        mData->setDataPosition(begin);
127    }
128    return ok;
129}
130
131// Check the key (i.e metadata id) is valid if it is a system one.
132// Loop over all the exiting ones in the Parcel to check for duplicate
133// (not allowed).
134bool Metadata::checkKey(int key)
135{
136    if (key < FIRST_SYSTEM_ID ||
137        (LAST_SYSTEM_ID < key && key < FIRST_CUSTOM_ID)) {
138        ALOGE("Bad key %d", key);
139        return false;
140    }
141    size_t curr = mData->dataPosition();
142    // Loop over the keys to check if it has been used already.
143    mData->setDataPosition(mBegin);
144
145    bool error = false;
146    size_t left = curr - mBegin;
147    while (left > 0) {
148        size_t pos = mData->dataPosition();
149        size_t size = mData->readInt32();
150        if (size < kRecordHeaderSize || size > left) {
151            error = true;
152            break;
153        }
154        if (mData->readInt32() == key) {
155            ALOGE("Key exists already %d", key);
156            error = true;
157            break;
158        }
159        mData->setDataPosition(pos + size);
160        left -= size;
161    }
162    mData->setDataPosition(curr);
163    return !error;
164}
165
166}  // namespace android::media
167}  // namespace android
168