PJSUA2: thread safety issue in list of objects

[nanang]

Currently PJSUA2 internally maintains some lists of objects, e.g: AudioMedia, Buddy, AudioDevInfo, VideoDevInfo, CodecInfo. Unfortunately some APIs for querying and modifying those lists are not really thread safe. For example Endpoint::mediaEnumPorts() will simply return the internal list, and Endpoint::mediaAdd(), Endpoint::mediaRemove(), Endpoint::mediaExists() may access the internal list without mutex protection. Another example is enumeration function such as Aud/VidDevManager::enumDev(), CodecInfoVector &codecEnum() that returns internal list which always be updated at each call of the function, so if two threads call the same function at the same time, one of the thread will get an invalid list. Thank you Niclas Larsson for the report.

Since those PJSUA2 objects are actually just kind of thin wrapper of PJSUA objects, e.g: PJSUA2 AudioMedia is wrapping PJSUA conference bridge port ID, those object should be easily generated from PJSUA. So instead of maintaining list of objects internally, PJSUA2 can simply generate the requested objects on the fly. For example when enumeration function is called, the function will generate the PJSUA2 objects, generate a new list containing those object, and return the list. This way PJSUA2 can also avoid adding another layer of synchronization as PJSUA already provides the thread safety.

This ticket will deprecate these APIs:

• AudioMedia related: AudioMediaVector, Endpoint::mediaEnumPorts(), Endpoint::mediaAdd(), Endpoint::mediaRemove(), Endpoint::mediaExists(), Endpoint::typecastFromMedia(), AudioMediaPlayer::typecastFromAudioMedia(), AudioMediaRecorder::typecastFromAudioMedia(), Endpoint::registerMediaPort()
• Buddy related: BuddyVector, Account::enumBuddies(), Account::findBuddy()
• Codec enumeration: CodecInfoVector, Endpoint::codecEnum(), Endpoint::videoCodecEnum()
• Audio/video device info: AudioDevInfoVector, VideoDevInfoVector, AudDevManager::enumDev(), VidDevManager::enumDev()

This ticket will introduce new APIs:

• AudioMedia related: AudioMediaVector2, Endpoint::mediaEnumPorts2(), Endpoint::registerMediaPort2()
• Buddy related: BuddyVector2, Account::enumBuddies2(), Account::findBuddy2()
• Codec enumeration: CodecInfoVector2, Endpoint::codecEnum2(), Endpoint::videoCodecEnum2()
• Audio/video device info: AudioDevInfoVector2, VideoDevInfoVector2, AudDevManager::enumDev2(), VidDevManager::enumDev2()