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