14.【cocos2d-x 源码分析】:Audio的详细分析
对应源码位置：cocos2d-x-3.3\cocos\audio\include\SimpleAudioEngine
SimpleAudioEngine的实现
SimpleAudioEngine是提供了简单的 播放音效，以及播放背景音乐的功能。
class EXPORT_DLL SimpleAudioEngine
{
public:
static SimpleAudioEngine* getInstance();
static void end();
protected:
SimpleAudioEngine();
virtual ~SimpleAudioEngine();
public:
//播放背景音乐
virtual void preloadBackgroundMusic(const char* pszFilePath);
virtual void playBackgroundMusic(const char* pszFilePath, bool bLoop = false);
virtual void stopBackgroundMusic(bool bReleaseData = false);
virtual void pauseBackgroundMusic();
virtual void resumeBackgroundMusic();
virtual void rewindBackgroundMusic();
virtual bool willPlayBackgroundMusic();
virtual bool isBackgroundMusicPlaying();
virtual float getBackgroundMusicVolume();
virtual void setBackgroundMusicVolume(float volume);
//播放音效
virtual float getEffectsVolume();
virtual void setEffectsVolume(float volume);
virtual unsigned int playEffect(const char* pszFilePath, bool bLoop = false,
float pitch = 1.0f, float pan = 0.0f, float gain = 1.0f);
virtual void pauseEffect(unsigned int nSoundId);
virtual void pauseAllEffects();
virtual void resumeEffect(unsigned int nSoundId);
virtual void resumeAllEffects();
virtual void stopEffect(unsigned int nSoundId);
virtual void stopAllEffects();
virtual void preloadEffect(const char* pszFilePath);
virtual void unloadEffect(const char* pszFilePath);
};
以win32下的实现为例：
//用于处理 音效 每个播放音效 对应一个MCI
typedef map<unsigned int, MciPlayer *> EffectList;
//用于播放 背景音乐
typedef pair<unsigned int, MciPlayer *> Effect;
static char s_szRootPath[MAX_PATH];
static DWORD s_dwRootLen;
static char s_szFullPath[MAX_PATH];
//获取全路径
static std::string _FullPath(const char * szPath);
//计算路径的hash值
static unsigned int _Hash(const char *key);
#define BREAK_IF(cond) if (cond) break;
//用于实现单例 音效
static EffectList& sharedList()
{
static EffectList s_List;
return s_List;
}
//用于实现单例 背景音乐
static MciPlayer& sharedMusic()
{
static MciPlayer s_Music;
return s_Music;
}
//单例模式
SimpleAudioEngine* SimpleAudioEngine::getInstance()
{
static SimpleAudioEngine s_SharedEngine;
return &s_SharedEngine;
}
//一个个都给删除了
void SimpleAudioEngine::end()
{
sharedMusic().Close();
EffectList::iterator p = sharedList().begin();
while (p != sharedList().end())
{
delete p->second;
p->second = NULL;
p++;
}
sharedList().clear();
return;
}
//////////////////////////////////////////////////////////////////////////
// BackgroundMusic
//////////////////////////////////////////////////////////////////////////
//直接加载 然后播放
void SimpleAudioEngine::playBackgroundMusic(const char* pszFilePath, bool bLoop)
{
if (! pszFilePath)
{
return;
}
sharedMusic().Open(_FullPath(pszFilePath).c_str(), _Hash(pszFilePath));
sharedMusic().Play((bLoop) ? -1 : 1);
}
void SimpleAudioEngine::stopBackgroundMusic(bool bReleaseData)
{
if (bReleaseData)
{
sharedMusic().Close();
}
else
{
sharedMusic().Stop();
}
}
void SimpleAudioEngine::pauseBackgroundMusic()
{
sharedMusic().Pause();
}
void SimpleAudioEngine::resumeBackgroundMusic()
{
sharedMusic().Resume();
}
void SimpleAudioEngine::rewindBackgroundMusic()
{
sharedMusic().Rewind();
}
//无语
bool SimpleAudioEngine::willPlayBackgroundMusic()
{
return false;
}
bool SimpleAudioEngine::isBackgroundMusicPlaying()
{
return sharedMusic().IsPlaying();
}
//////////////////////////////////////////////////////////////////////////
// effect function
//////////////////////////////////////////////////////////////////////////
//传了那么多参数 假的
unsigned int SimpleAudioEngine::playEffect(const char* pszFilePath, bool bLoop,
float pitch, float pan, float gain)
{
unsigned int nRet = _Hash(pszFilePath);
//先预加载
preloadEffect(pszFilePath);
//此时必然能找到
EffectList::iterator p = sharedList().find(nRet);
if (p != sharedList().end())
{
p->second->Play((bLoop) ? -1 : 1);
}
return nRet;
}
//stop某一个
void SimpleAudioEngine::stopEffect(unsigned int nSoundId)
{
EffectList::iterator p = sharedList().find(nSoundId);
if (p != sharedList().end())
{
p->second->Stop();
}
}
void SimpleAudioEngine::preloadEffect(const char* pszFilePath)
{
int nRet = 0;
do
{
BREAK_IF(! pszFilePath);
nRet = _Hash(pszFilePath);
BREAK_IF(sharedList().end() != sharedList().find(nRet));
sharedList().insert(Effect(nRet, new MciPlayer()));
MciPlayer * pPlayer = sharedList()[nRet];
//就是 new一个MciPlayer 加入到表项中
//让他加载该音效
pPlayer->Open(_FullPath(pszFilePath).c_str(), nRet);
//成功的 加载之后是走不下去的 所以没问题
BREAK_IF(nRet == pPlayer->GetSoundID());
delete pPlayer;
sharedList().erase(nRet);
nRet = 0;
} while (0);
}
//暂停某一个
void SimpleAudioEngine::pauseEffect(unsigned int nSoundId)
{
EffectList::iterator p = sharedList().find(nSoundId);
if (p != sharedList().end())
{
p->second->Pause();
}
}
//暂停所有的音效
void SimpleAudioEngine::pauseAllEffects()
{
EffectList::iterator iter;
for (iter = sharedList().begin(); iter != sharedList().end(); iter++)
{
iter->second->Pause();
}
}
//找到某一个 然后恢复
void SimpleAudioEngine::resumeEffect(unsigned int nSoundId)
{
EffectList::iterator p = sharedList().find(nSoundId);
if (p != sharedList().end())
{
p->second->Resume();
}
}
//对列表中 都恢复
void SimpleAudioEngine::resumeAllEffects()
{
EffectList::iterator iter;
for (iter = sharedList().begin(); iter != sharedList().end(); iter++)
{
iter->second->Resume();
}
}
//对列表中每一个 都stop
void SimpleAudioEngine::stopAllEffects()
{
EffectList::iterator iter;
for (iter = sharedList().begin(); iter != sharedList().end(); iter++)
{
iter->second->Stop();
}
}
//假装的
void SimpleAudioEngine::preloadBackgroundMusic(const char* pszFilePath)
{
}
//简单的从map中删去
void SimpleAudioEngine::unloadEffect(const char* pszFilePath)
{
unsigned int nID = _Hash(pszFilePath);
EffectList::iterator p = sharedList().find(nID);
if (p != sharedList().end())
{
delete p->second;
p->second = NULL;
sharedList().erase(nID);
}
}
//////////////////////////////////////////////////////////////////////////
// volume interface
//////////////////////////////////////////////////////////////////////////
float SimpleAudioEngine::getBackgroundMusicVolume()
{
return 1.0;
}
//假装的 没有实现
void SimpleAudioEngine::setBackgroundMusicVolume(float volume)
{
}
float SimpleAudioEngine::getEffectsVolume()
{
return 1.0;
}
void SimpleAudioEngine::setEffectsVolume(float volume)
{
}
//////////////////////////////////////////////////////////////////////////
// static function
//////////////////////////////////////////////////////////////////////////
//获取完整路径
static std::string _FullPath(const char * szPath)
{
return FileUtils::getInstance()->fullPathForFilename(szPath);
}
//计算hash
unsigned int _Hash(const char *key)
{
unsigned int len = strlen(key);
const char *end=key+len;
unsigned int hash;
for (hash = 0; key < end; key++)
{
hash *= 16777619;
hash ^= (unsigned int) (unsigned char) toupper(*key);
}
return (hash);
}
MciPlayer 的实现
可以看出来 SimpleAudioEngine的所有操作都是转交给了MciPlayer。
class MciPlayer
{
public:
MciPlayer();
~MciPlayer();
void Close();
void Open(const char* pFileName, UINT uId);
void Play(UINT uTimes = 1);
void Pause();
void Resume();
void Stop();
void Rewind();
bool IsPlaying();
UINT GetSoundID();
private:
friend LRESULT WINAPI _SoundPlayProc(HWND hWnd, UINT Msg, WPARAM wParam, LPARAM lParam);
void _SendGenericCommand(int nCommand, DWORD_PTR param1 = 0, DWORD_PTR parma2 = 0);
HWND _wnd;
MCIDEVICEID _dev;
UINT _soundID;
UINT _times;
bool _playing;
std::string strExt;
};
//其实现是对MCI命令的包装
void MciPlayer::Open(const char* pFileName, UINT uId)
{
do
{
BREAK_IF(! pFileName || ! _wnd);
int nLen = (int)strlen(pFileName);
BREAK_IF(! nLen);
std::string strFile(pFileName);
int nPos = strFile.rfind(".") + 1;
strExt = strFile.substr(nPos, strFile.length() - nPos);
Close();
MCI_OPEN_PARMS mciOpen = {0};
MCIERROR mciError;
mciOpen.lpstrDeviceType = (LPCTSTR)MCI_ALL_DEVICE_ID;
WCHAR* fileNameWideChar = new WCHAR[nLen + 1];
BREAK_IF(! fileNameWideChar);
MultiByteToWideChar(CP_ACP, 0, pFileName, nLen + 1, fileNameWideChar, nLen + 1);
mciOpen.lpstrElementName = fileNameWideChar;
mciError = mciSendCommand(0,MCI_OPEN, MCI_OPEN_ELEMENT, reinterpret_cast<DWORD_PTR>(&mciOpen));
CC_SAFE_DELETE_ARRAY(mciOpen.lpstrElementName);
BREAK_IF(mciError);
_dev = mciOpen.wDeviceID;
_soundID = uId;
_playing = false;
} while (0);
}
void MciPlayer::Play(UINT uTimes /* = 1 */)
{
if (! _dev)
{
return;
}
MCI_PLAY_PARMS mciPlay = {0};
mciPlay.dwCallback = reinterpret_cast<DWORD_PTR>(_wnd);
s_mciError = mciSendCommand(_dev,MCI_PLAY, MCI_FROM|MCI_NOTIFY,reinterpret_cast<DWORD_PTR>(&mciPlay));
if (! s_mciError)
{
_playing = true;
_times = uTimes;
}
}
void MciPlayer::Close()
{
if (_playing)
{
Stop();
}
if (_dev)
{
_SendGenericCommand(MCI_CLOSE);
}
_dev = 0;
_playing = false;
}
void MciPlayer::Pause()
{
_SendGenericCommand(MCI_PAUSE);
}
void MciPlayer::Resume()
{
if (strExt == "mid" || strExt == "MID")
{
// midi not supprt MCI_RESUME, should get the position and use MCI_FROM
MCI_STATUS_PARMS mciStatusParms;
MCI_PLAY_PARMS mciPlayParms;
mciStatusParms.dwItem = MCI_STATUS_POSITION;
_SendGenericCommand(MCI_STATUS, MCI_STATUS_ITEM, reinterpret_cast<DWORD_PTR>(&mciStatusParms)); // MCI_STATUS
mciPlayParms.dwFrom = mciStatusParms.dwReturn; // get position
_SendGenericCommand(MCI_PLAY, MCI_FROM, reinterpret_cast<DWORD_PTR>(&mciPlayParms)); // MCI_FROM
}
else
{
_SendGenericCommand(MCI_RESUME);
}
}
最后
下一篇分析 localStorage 的实现。