axmol/cocos/audio/apple/AudioEngineImpl.mm

/****************************************************************************
 Copyright (c) 2014-2016 Chukong Technologies Inc.
 Copyright (c) 2017-2018 Xiamen Yaji Software Co., Ltd.
 Copyright (c) 2018-2020 HALX99.

 http://www.cocos2d-x.org

 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
 in the Software without restriction, including without limitation the rights
 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 copies of the Software, and to permit persons to whom the Software is
 furnished to do so, subject to the following conditions:

 The above copyright notice and this permission notice shall be included in
 all copies or substantial portions of the Software.

 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
 ****************************************************************************/
#define LOG_TAG "AudioEngineImpl"

#include "platform/CCPlatformConfig.h"
#if CC_TARGET_PLATFORM == CC_PLATFORM_IOS || CC_TARGET_PLATFORM == CC_PLATFORM_MAC

#include "audio/apple/AudioEngineImpl.h"

#import <OpenAL/alc.h>
#import <AVFoundation/AVFoundation.h>

#include "audio/include/AudioEngine.h"
#include "platform/CCFileUtils.h"
#include "base/CCDirector.h"
#include "base/CCScheduler.h"
#include "base/ccUtils.h"

#if CC_TARGET_PLATFORM == CC_PLATFORM_IOS
#import <UIKit/UIKit.h>
#endif

using namespace cocos2d;

static ALCdevice* s_ALDevice = nullptr;
static ALCcontext* s_ALContext = nullptr;
static AudioEngineImpl* s_instance = nullptr;

typedef ALvoid (*alSourceNotificationProc)(ALuint sid, ALuint notificationID, ALvoid* userData);
typedef ALenum (*alSourceAddNotificationProcPtr)(ALuint sid, ALuint notificationID, alSourceNotificationProc notifyProc, ALvoid* userData);
static ALenum alSourceAddNotificationExt(ALuint sid, ALuint notificationID, alSourceNotificationProc notifyProc, ALvoid* userData)
{
    static alSourceAddNotificationProcPtr proc = nullptr;

    if (proc == nullptr)
    {
        proc = (alSourceAddNotificationProcPtr)alcGetProcAddress(nullptr, "alSourceAddNotification");
    }

    if (proc)
    {
        return proc(sid, notificationID, notifyProc, userData);
    }
    return AL_INVALID_VALUE;
}

#if CC_TARGET_PLATFORM == CC_PLATFORM_IOS
@interface AudioEngineSessionHandler : NSObject
{
}

-(id) init;
-(void)handleInterruption:(NSNotification*)notification;

@end

@implementation AudioEngineSessionHandler

// only enable it on iOS. Disable it on tvOS
#if !defined(CC_TARGET_OS_TVOS)
void AudioEngineInterruptionListenerCallback(void* user_data, UInt32 interruption_state)
{
    if (kAudioSessionBeginInterruption == interruption_state)
    {
      alcMakeContextCurrent(nullptr);
    }
    else if (kAudioSessionEndInterruption == interruption_state)
    {
      OSStatus result = AudioSessionSetActive(true);
      if (result) NSLog(@"Error setting audio session active! %d\n", static_cast<int>(result));

      alcMakeContextCurrent(s_ALContext);
    }
}
#endif

-(id) init
{
    if (self = [super init])
    {
      if ([[[UIDevice currentDevice] systemVersion] intValue] > 5) {
          [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(handleInterruption:) name:AVAudioSessionInterruptionNotification object:[AVAudioSession sharedInstance]];
          [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(handleInterruption:) name:UIApplicationDidBecomeActiveNotification object:nil];
          [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(handleInterruption:) name:UIApplicationWillResignActiveNotification object:nil];
      }
    // only enable it on iOS. Disable it on tvOS
    // AudioSessionInitialize removed from tvOS
#if !defined(CC_TARGET_OS_TVOS)
      else {
        AudioSessionInitialize(NULL, NULL, AudioEngineInterruptionListenerCallback, self);
      }
#endif
    
    BOOL success = [[AVAudioSession sharedInstance]
                    setCategory: AVAudioSessionCategoryAmbient
                    error: nil];
    if (!success)
        ALOGE("Fail to set audio session.");
    }
    return self;
}

-(void)handleInterruption:(NSNotification*)notification
{
    static bool isAudioSessionInterrupted = false;
    static bool resumeOnBecomingActive = false;
    static bool pauseOnResignActive = false;

    if ([notification.name isEqualToString:AVAudioSessionInterruptionNotification])
    {
        NSInteger reason = [[[notification userInfo] objectForKey:AVAudioSessionInterruptionTypeKey] integerValue];
        if (reason == AVAudioSessionInterruptionTypeBegan)
        {
            isAudioSessionInterrupted = true;

            if ([UIApplication sharedApplication].applicationState != UIApplicationStateActive)
            {
                ALOGD("AVAudioSessionInterruptionTypeBegan, application != UIApplicationStateActive, alcMakeContextCurrent(nullptr)");
                alcMakeContextCurrent(nullptr);
            }
            else
            {
                ALOGD("AVAudioSessionInterruptionTypeBegan, application == UIApplicationStateActive, pauseOnResignActive = true");
                pauseOnResignActive = true;
            }
        }

        if (reason == AVAudioSessionInterruptionTypeEnded)
        {
            isAudioSessionInterrupted = false;

            if ([UIApplication sharedApplication].applicationState == UIApplicationStateActive)
            {
                ALOGD("AVAudioSessionInterruptionTypeEnded, application == UIApplicationStateActive, alcMakeContextCurrent(s_ALContext)");
                NSError *error = nil;
                [[AVAudioSession sharedInstance] setActive:YES error:&error];
                if (alcGetCurrentContext() != nullptr) 
                    alcMakeContextCurrent(nullptr);
                alcMakeContextCurrent(s_ALContext);
                if (Director::getInstance()->isPaused())
                {
                    ALOGD("AVAudioSessionInterruptionTypeEnded, director was paused, try to resume it.");
                    Director::getInstance()->resume();
                }
            }
            else
            {
                ALOGD("AVAudioSessionInterruptionTypeEnded, application != UIApplicationStateActive, resumeOnBecomingActive = true");
                resumeOnBecomingActive = true;
            }
        }
    }
    else if ([notification.name isEqualToString:UIApplicationWillResignActiveNotification])
    {
        ALOGD("UIApplicationWillResignActiveNotification");
        if (pauseOnResignActive)
        {
            pauseOnResignActive = false;
            ALOGD("UIApplicationWillResignActiveNotification, alcMakeContextCurrent(nullptr)");
            alcMakeContextCurrent(nullptr);
        }
    }
    else if ([notification.name isEqualToString:UIApplicationDidBecomeActiveNotification])
    {
        ALOGD("UIApplicationDidBecomeActiveNotification");
        if (resumeOnBecomingActive)
        {
            resumeOnBecomingActive = false;
            ALOGD("UIApplicationDidBecomeActiveNotification, alcMakeContextCurrent(s_ALContext)");
            NSError *error = nil;
            BOOL success = [[AVAudioSession sharedInstance] setCategory: AVAudioSessionCategoryAmbient error: &error];
            if (!success) {
                ALOGE("Fail to set audio session.");
                return;
            }
            [[AVAudioSession sharedInstance] setActive:YES error:&error];
            
            if (alcGetCurrentContext() != nullptr) 
                alcMakeContextCurrent(nullptr);
            alcMakeContextCurrent(s_ALContext);
        }
        else if (isAudioSessionInterrupted)
        {
            ALOGD("Audio session is still interrupted, pause director!");
            // Director::getInstance()->pause();
        }
    }
}

-(void) dealloc
{
    [[NSNotificationCenter defaultCenter] removeObserver:self name:AVAudioSessionInterruptionNotification object:nil];
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIApplicationDidBecomeActiveNotification object:nil];
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIApplicationWillResignActiveNotification object:nil];

    [super dealloc];
}
@end

static id s_AudioEngineSessionHandler = nullptr;
#endif

ALvoid AudioEngineImpl::myAlSourceNotificationCallback(ALuint sid, ALuint notificationID, ALvoid* userData)
{
    // Currently, we only care about AL_BUFFERS_PROCESSED event
    if (notificationID != AL_BUFFERS_PROCESSED)
        return;

    AudioPlayer* player = nullptr;
    s_instance->_threadMutex.lock();
    for (const auto& e : s_instance->_audioPlayers)
    {
        player = e.second;
        if (player->_alSource == sid && player->_streamingSource)
        {
            player->wakeupRotateThread();
        }
    }
    s_instance->_threadMutex.unlock();
}

AudioEngineImpl::AudioEngineImpl()
: _lazyInitLoop(true)
, _currentAudioID(0)
, _scheduler(nullptr)
{
    s_instance = this;
}

AudioEngineImpl::~AudioEngineImpl()
{
    if (_scheduler != nullptr)
    {
        _scheduler->unschedule(CC_SCHEDULE_SELECTOR(AudioEngineImpl::update), this);
    }

    if (s_ALContext) {
        alDeleteSources(MAX_AUDIOINSTANCES, _alSources);

        _audioCaches.clear();

        alcMakeContextCurrent(nullptr);
        alcDestroyContext(s_ALContext);
    }
    if (s_ALDevice) {
        alcCloseDevice(s_ALDevice);
    }

#if CC_TARGET_PLATFORM == CC_PLATFORM_IOS
    [s_AudioEngineSessionHandler release];
#endif
    s_instance = nullptr;
}

bool AudioEngineImpl::init()
{
    bool ret = false;
    do{
#if CC_TARGET_PLATFORM == CC_PLATFORM_IOS
        s_AudioEngineSessionHandler = [[AudioEngineSessionHandler alloc] init];
#endif

        s_ALDevice = alcOpenDevice(nullptr);

        if (s_ALDevice) {
            s_ALContext = alcCreateContext(s_ALDevice, nullptr);
            alcMakeContextCurrent(s_ALContext);

            alGenSources(MAX_AUDIOINSTANCES, _alSources);
            auto alError = alGetError();
            if(alError != AL_NO_ERROR)
            {
                ALOGE("%s:generating sources failed! error = %x", __PRETTY_FUNCTION__, alError);
                break;
            }

            for (int i = 0; i < MAX_AUDIOINSTANCES; ++i) {
                _unusedSourcesPool.push_back(_alSources[i]);
                alSourceAddNotificationExt(_alSources[i], AL_BUFFERS_PROCESSED, myAlSourceNotificationCallback, nullptr);
            }

            // fixed #16170: Random crash in alGenBuffers(AudioCache::readDataTask) at startup
            // Please note that, as we know the OpenAL operation is atomic (threadsafe),
            // 'alGenBuffers' may be invoked by different threads. But in current implementation of 'alGenBuffers',
            // When the first time it's invoked, application may crash!!!
            // Why? OpenAL is opensource by Apple and could be found at
            // http://opensource.apple.com/source/OpenAL/OpenAL-48.7/Source/OpenAL/oalImp.cpp .
            /*

            void InitializeBufferMap()
            {
                if (gOALBufferMap == NULL) // Position 1
                {
                    gOALBufferMap = new OALBufferMap ();  // Position 2

                    // Position Gap

                    gBufferMapLock = new CAGuard("OAL:BufferMapLock"); // Position 3
                    gDeadOALBufferMap = new OALBufferMap ();

                    OALBuffer   *newBuffer = new OALBuffer (AL_NONE);
                    gOALBufferMap->Add(AL_NONE, &newBuffer);
                }
            }

            AL_API ALvoid AL_APIENTRY alGenBuffers(ALsizei n, ALuint *bids)
            {
                ...

                try {
                    if (n < 0)
                    throw ((OSStatus) AL_INVALID_VALUE);

                    InitializeBufferMap();
                    if (gOALBufferMap == NULL)
                    throw ((OSStatus) AL_INVALID_OPERATION);

                    CAGuard::Locker locked(*gBufferMapLock);  // Position 4
                ...
                ...
            }

             */
            // 'gBufferMapLock' will be initialized in the 'InitializeBufferMap' function,
            // that's the problem. It means that 'InitializeBufferMap' may be invoked in different threads.
            // It will be very dangerous in multi-threads environment.
            // Imagine there're two threads (Thread A, Thread B), they call 'alGenBuffers' simultaneously.
            // While A goto 'Position Gap', 'gOALBufferMap' was assigned, then B goto 'Position 1' and find
            // that 'gOALBufferMap' isn't NULL, B just jump over 'InitialBufferMap' and goto 'Position 4'.
            // Meanwhile, A is still at 'Position Gap', B will crash at '*gBufferMapLock' since 'gBufferMapLock'
            // is still a null pointer. Oops, how could Apple implemented this method in this fucking way?

            // Workaround is do an unused invocation in the mainthread right after OpenAL is initialized successfully
            // as bellow.
            // ================ Workaround begin ================ //

            ALuint unusedAlBufferId = 0;
            alGenBuffers(1, &unusedAlBufferId);
            alDeleteBuffers(1, &unusedAlBufferId);

            // ================ Workaround end ================ //

            _scheduler = Director::getInstance()->getScheduler();
            ret = true;
            ALOGI("OpenAL was initialized successfully!");
        }
    }while (false);

    return ret;
}

AudioCache* AudioEngineImpl::preload(const std::string& filePath, std::function<void(bool)> callback)
{
    AudioCache* audioCache = nullptr;

    auto it = _audioCaches.find(filePath);
    if (it == _audioCaches.end()) {
        audioCache = &_audioCaches[filePath];
        audioCache->_fileFullPath = FileUtils::getInstance()->fullPathForFilename(filePath);
        unsigned int cacheId = audioCache->_id;
        auto isCacheDestroyed = audioCache->_isDestroyed;
        AudioEngine::addTask([audioCache, cacheId, isCacheDestroyed](){
            if (*isCacheDestroyed)
            {
                ALOGV("AudioCache (id=%u) was destroyed, no need to launch readDataTask.", cacheId);
                audioCache->setSkipReadDataTask(true);
                return;
            }
            audioCache->readDataTask(cacheId);
        });
    }
    else {
        audioCache = &it->second;
    }

    if (audioCache && callback)
    {
        audioCache->addLoadCallback(callback);
    }
    return audioCache;
}

AUDIO_ID AudioEngineImpl::play2d(const std::string &filePath ,bool loop ,float volume)
{
    if (s_ALDevice == nullptr) {
        return AudioEngine::INVALID_AUDIO_ID;
    }

    ALuint alSource = findValidSource();
    if (alSource == AL_INVALID)
    {
        return AudioEngine::INVALID_AUDIO_ID;
    }

    auto player = new (std::nothrow) AudioPlayer;
    if (player == nullptr) {
        return AudioEngine::INVALID_AUDIO_ID;
    }

    player->_alSource = alSource;
    player->_loop = loop;
    player->_volume = volume;

    auto audioCache = preload(filePath, nullptr);
    if (audioCache == nullptr) {
        delete player;
        return AudioEngine::INVALID_AUDIO_ID;
    }

    player->setCache(audioCache);
    _threadMutex.lock();
    _audioPlayers.emplace(++_currentAudioID, player);
    _threadMutex.unlock();

    audioCache->addPlayCallback(std::bind(&AudioEngineImpl::_play2d,this,audioCache,_currentAudioID));

    if (_lazyInitLoop) {
        _lazyInitLoop = false;
        _scheduler->schedule(CC_SCHEDULE_SELECTOR(AudioEngineImpl::update), this, 0.05f, false);
    }

    return _currentAudioID;
}

void AudioEngineImpl::_play2d(AudioCache *cache, AUDIO_ID audioID)
{
    std::unique_lock<std::recursive_mutex> lck(_threadMutex);
    auto iter = _audioPlayers.find(audioID);
    if (iter == _audioPlayers.end())
        return;
    auto player = iter->second;

    //Note: It maybe in sub thread or main thread :(
    if (!*cache->_isDestroyed && cache->_state == AudioCache::State::READY)
    {
        if (player->play2d()) {
            _scheduler->performFunctionInCocosThread([audioID](){

                if (AudioEngine::_audioIDInfoMap.find(audioID) != AudioEngine::_audioIDInfoMap.end()) {
                    AudioEngine::_audioIDInfoMap[audioID].state = AudioEngine::AudioState::PLAYING;
                }
            });
        }
    }
    else
    {
        ALOGD("AudioEngineImpl::_play2d, cache was destroyed or not ready!");
        player->_removeByAudioEngine = true;
    }
}

ALuint AudioEngineImpl::findValidSource()
{
    ALuint sourceId = AL_INVALID;
    if (!_unusedSourcesPool.empty())
    {
        sourceId = _unusedSourcesPool.front();
        _unusedSourcesPool.pop_front();
    }

    return sourceId;
}

void AudioEngineImpl::setVolume(AUDIO_ID audioID,float volume)
{
    std::unique_lock<std::recursive_mutex> lck(_threadMutex);
    auto iter = _audioPlayers.find(audioID);
    if(iter == _audioPlayers.end())
        return;
    
    auto player = iter->second;
    lck.unlock();
    
    player->_volume = volume;

    if (player->_ready) {
        alSourcef(player->_alSource, AL_GAIN, volume);

        auto error = alGetError();
        if (error != AL_NO_ERROR) {
            ALOGE("%s: audio id = " AUDIO_ID_PRID ", error = %x", __PRETTY_FUNCTION__,audioID,error);
        }
    }
}

void AudioEngineImpl::setLoop(AUDIO_ID audioID, bool loop)
{
    std::unique_lock<std::recursive_mutex> lck(_threadMutex);
    auto iter = _audioPlayers.find(audioID);
    if(iter == _audioPlayers.end())
        return;
    
    auto player = iter->second;

    lck.unlock();
    
    if (player->_ready) {
        if (player->_streamingSource) {
            player->setLoop(loop);
        } else {
            if (loop) {
                alSourcei(player->_alSource, AL_LOOPING, AL_TRUE);
            } else {
                alSourcei(player->_alSource, AL_LOOPING, AL_FALSE);
            }

            auto error = alGetError();
            if (error != AL_NO_ERROR) {
                ALOGE("%s: audio id = " AUDIO_ID_PRID ", error = %x", __PRETTY_FUNCTION__,audioID,error);
            }
        }
    }
    else {
        player->_loop = loop;
    }
}

bool AudioEngineImpl::pause(AUDIO_ID audioID)
{
    std::unique_lock<std::recursive_mutex> lck(_threadMutex);
    auto iter = _audioPlayers.find(audioID);
    if(iter == _audioPlayers.end())
        return false;
    
    auto player = iter->second;
    
    lck.unlock();
    
    bool ret = true;
    alSourcePause(player->_alSource);

    auto error = alGetError();
    if (error != AL_NO_ERROR) {
        ret = false;
        ALOGE("%s: audio id = " AUDIO_ID_PRID ", error = %x", __PRETTY_FUNCTION__,audioID,error);
    }

    return ret;
}

bool AudioEngineImpl::resume(AUDIO_ID audioID)
{
    bool ret = true;
    std::unique_lock<std::recursive_mutex> lck(_threadMutex);
    auto iter = _audioPlayers.find(audioID);
    if(iter == _audioPlayers.end())
        return false;
    
    auto player = iter->second;
    lck.unlock();
    
    alSourcePlay(player->_alSource);

    auto error = alGetError();
    if (error != AL_NO_ERROR) {
        ret = false;
        ALOGE("%s: audio id = " AUDIO_ID_PRID ", error = %x", __PRETTY_FUNCTION__,audioID,error);
    }

    return ret;
}

void AudioEngineImpl::stop(AUDIO_ID audioID)
{
    std::unique_lock<std::recursive_mutex> lck(_threadMutex);
    auto iter = _audioPlayers.find(audioID);
    if(iter == _audioPlayers.end())
        return;
    
    auto player = iter->second;

    player->destroy();

    // Call 'update' method to cleanup immediately since the schedule may be cancelled without any notification.
    _updateLocked(0.0f);
}

void AudioEngineImpl::stopAll()
{
    std::lock_guard<std::recursive_mutex> lck(_threadMutex);
    for(auto&& player : _audioPlayers)
    {
        player.second->destroy();
    }
    //Note: Don't set the flag to false here, it should be set in 'update' function.
    // Otherwise, the state got from alSourceState may be wrong
//    for(int index = 0; index < MAX_AUDIOINSTANCES; ++index)
//    {
//        _alSourceUsed[_alSources[index]] = false;
//    }

    // Call 'update' method to cleanup immediately since the schedule may be cancelled without any notification.
    _updateLocked(0.0f);
}

float AudioEngineImpl::getDuration(AUDIO_ID audioID)
{
    std::lock_guard<std::recursive_mutex> lck(_threadMutex);
    auto it = _audioPlayers.find(audioID);
    if (it != _audioPlayers.end()) {
        auto player = it->second;
        if (player->_ready) {
            return player->_audioCache->_duration;
        }
    }
    return AudioEngine::TIME_UNKNOWN;
}

float AudioEngineImpl::getCurrentTime(AUDIO_ID audioID)
{
    std::unique_lock<std::recursive_mutex> lck(_threadMutex);
    auto it = _audioPlayers.find(audioID); 
    if (it == _audioPlayers.end())
        return 0.0f;

    float ret = 0.0f;
    auto player = it->second;
    if (player->_ready) {
        if (player->_streamingSource) {
            ret = player->getTime();
        }
        else {
            alGetSourcef(player->_alSource, AL_SEC_OFFSET, &ret);

            auto error = alGetError();
            if (error != AL_NO_ERROR) {
                ALOGE("%s, audio id:" AUDIO_ID_PRID ",error code:%x", __PRETTY_FUNCTION__, audioID, error);
            }
        }
    }

    return ret;
}

bool AudioEngineImpl::setCurrentTime(AUDIO_ID audioID, float time)
{
    bool ret = false;
    std::unique_lock<std::recursive_mutex> lck(_threadMutex);
    auto iter = _audioPlayers.find(audioID);
    if(iter == _audioPlayers.end())
        return false;
    
    auto player = iter->second;

    do {
        if (!player->_ready) {
            break;
        }

        if (player->_streamingSource) {
            ret = player->setTime(time);
            break;
        }
        else {
            if (player->_audioCache->_framesRead != player->_audioCache->_totalFrames &&
                (time * player->_audioCache->_sampleRate) > player->_audioCache->_framesRead) {
                ALOGE("%s: audio id = " AUDIO_ID_PRID, __PRETTY_FUNCTION__,audioID);
                break;
            }

            alSourcef(player->_alSource, AL_SEC_OFFSET, time);

            auto error = alGetError();
            if (error != AL_NO_ERROR) {
                ALOGE("%s: audio id = " AUDIO_ID_PRID ", error = %x", __PRETTY_FUNCTION__,audioID,error);
            }
            ret = true;
        }
    } while (0);

    return ret;
}

void AudioEngineImpl::setFinishCallback(AUDIO_ID audioID, const std::function<void (AUDIO_ID, const std::string &)> &callback)
{
    std::unique_lock<std::recursive_mutex> lck(_threadMutex);
    auto iter = _audioPlayers.find(audioID);
    if(iter == _audioPlayers.end())
        return;
    
    auto player = iter->second;
    lck.unlock();
    
    player->_finishCallbak = callback;
}

void AudioEngineImpl::update(float dt)
{
    std::unique_lock<std::recursive_mutex> lck(_threadMutex);
    _updateLocked(dt);
}

void AudioEngineImpl::_updateLocked(float dt)
{
    AUDIO_ID audioID;
    AudioPlayer* player;
    ALuint alSource;

//    ALOGV("AudioPlayer count: %d", (int)_audioPlayers.size());
    for (auto it = _audioPlayers.begin(); it != _audioPlayers.end(); ) {
        audioID = it->first;
        player = it->second;
        alSource = player->_alSource;

        if (player->_removeByAudioEngine)
        {
            AudioEngine::remove(audioID);
            
            it = _audioPlayers.erase(it);
            delete player;
            _unusedSourcesPool.push_back(alSource);
        }
        else if (player->_ready && player->isFinished()) {

            std::string filePath;
            if (player->_finishCallbak) {
                auto& audioInfo = AudioEngine::_audioIDInfoMap[audioID];
                filePath = audioInfo.filePath;
            }

            AudioEngine::remove(audioID);
            
            it = _audioPlayers.erase(it);

            if (player->_finishCallbak) {
                /// ###IMPORTANT: don't call immidiately, because at callback, user-end may play a new audio
                /// cause _audioPlayers' iterator goan to invalid.
                _finishCallbacks.push_back([finishCallback = std::move(player->_finishCallbak), audioID, filePath = std::move(filePath)](){
                    finishCallback(audioID, filePath); // FIXME: callback will delay 50ms
                });
            }
            // clear cache when audio player finsihed properly
            player->setCache(nullptr);
            delete player;
            _unusedSourcesPool.push_back(alSource);
        }
        else{
            ++it;
        }
    }

    if(_audioPlayers.empty()) {
        _lazyInitLoop = true;
        _scheduler->unschedule(CC_SCHEDULE_SELECTOR(AudioEngineImpl::update), this);
    }
    if (!_finishCallbacks.empty()) {
        for (auto& finishCallback : _finishCallbacks)
            finishCallback();
        _finishCallbacks.clear();
    }
}

void AudioEngineImpl::uncache(const std::string &filePath)
{
    _audioCaches.erase(filePath);
}

void AudioEngineImpl::uncacheAll()
{   
    // prevent player hold invalid AudioCache* pointer, since all audio caches purged
    for(auto& player : _audioPlayers)
        player.second->setCache(nullptr);

    _audioCaches.clear();
}

#endif