Method getWriteVector

3rdparty/openal/common/ringbuffer.cpp:194–223

}

auto RingBuffer::getWriteVector() const noexcept -> DataPair
{
    DataPair ret;

    std::size_t w{mWritePtr.load(std::memory_order_acquire)};
    std::size_t r{mReadPtr.load(std::memory_order_acquire) + mWriteSize - mSizeMask};
    w &= mSizeMask;
    r &= mSizeMask;
    const std::size_t free_cnt{(r-w-1) & mSizeMask};

    const std::size_t cnt2{w + free_cnt};
    if(cnt2 > mSizeMask+1)
    {
        /* Two part vector: the rest of the buffer after the current write ptr,
         * plus some from the start of the buffer. */
        ret.first.buf = const_cast<std::byte*>(mBuffer.data() + w*mElemSize);
        ret.first.len = mSizeMask+1 - w;
        ret.second.buf = const_cast<std::byte*>(mBuffer.data());
        ret.second.len = cnt2 & mSizeMask;
    }
    else
    {
        ret.first.buf = const_cast<std::byte*>(mBuffer.data() + w*mElemSize);
        ret.first.len = free_cnt;
        ret.second.buf = nullptr;
        ret.second.len = 0;
    }

    return ret;
}