Function GetSourceSecOffset

3rdparty/openal/al/source.cpp:225–274

GetSourceSecOffset * * Gets the current read offset for the given Source, in seconds. The offset is * relative to the start of the queue (not the start of the current buffer). */

 * relative to the start of the queue (not the start of the current buffer).
 */
ALdouble GetSourceSecOffset(ALsource *Source, ALCcontext *context, nanoseconds *clocktime)
{
    ALCdevice *device{context->mDevice.get()};
    const ALbufferlistitem *Current;
    uint64_t readPos;
    ALuint refcount;
    ALvoice *voice;

    do {
        Current = nullptr;
        readPos = 0;
        while(((refcount=device->MixCount.load(std::memory_order_acquire))&1))
            std::this_thread::yield();
        *clocktime = GetDeviceClockTime(device);

        voice = GetSourceVoice(Source, context);
        if(voice)
        {
            Current = voice->mCurrentBuffer.load(std::memory_order_relaxed);

            readPos  = uint64_t{voice->mPosition.load(std::memory_order_relaxed)} << FRACTIONBITS;
            readPos |= voice->mPositionFrac.load(std::memory_order_relaxed);
        }
        std::atomic_thread_fence(std::memory_order_acquire);
    } while(refcount != device->MixCount.load(std::memory_order_relaxed));

    ALdouble offset{0.0};
    if(voice)
    {
        const ALbufferlistitem *BufferList{Source->queue};
        const ALbuffer *BufferFmt{nullptr};
        while(BufferList && BufferList != Current)
        {
            if(!BufferFmt) BufferFmt = BufferList->mBuffer;
            readPos += uint64_t{BufferList->mSampleLen} << FRACTIONBITS;
            BufferList = BufferList->mNext.load(std::memory_order_relaxed);
        }

        while(BufferList && !BufferFmt)
        {
            BufferFmt = BufferList->mBuffer;
            BufferList = BufferList->mNext.load(std::memory_order_relaxed);
        }
        assert(BufferFmt != nullptr);

        offset = static_cast<ALdouble>(readPos) / ALdouble{FRACTIONONE} / BufferFmt->Frequency;
    }

    return offset;
}

/* GetSourceOffset
 *