Title Storage から blob をダウンロードする

std::unique_ptr<std::vector<uint8_t>> downloadBlobBuffer = std::make_unique<std::vector<uint8_t>>(blobMetadata.length);

auto asyncBlock = std::make_unique<XAsyncBlock>();
asyncBlock->queue = queue;
asyncBlock->context = downloadBlobBuffer.get();
asyncBlock->callback = [](XAsyncBlock* asyncBlock)
{
    std::unique_ptr<XAsyncBlock> asyncBlockPtr{ asyncBlock };   // Take over ownership of XAsyncBlock*.
    std::unique_ptr<std::vector<uint8_t>> downloadBlobBuffer{ static_cast<std::vector<uint8_t>*>(asyncBlock->context) };
    HRESULT hr = XblTitleStorageDownloadBlobResult(asyncBlock, &blobMetadata);
};

HRESULT hr = XblTitleStorageDownloadBlobAsync(
    xboxLiveContext,
    blobMetadata,
    downloadBlobBuffer->data(),
    blobMetadata.length,
    XblTitleStorageETagMatchCondition::NotUsed,
    selectQuery.c_str(),   // Optional  .
    preferredDownloadBlockSize,   // Optional.
    asyncBlock.get()
);

if (SUCCEEDED(hr))
{
    // The call succeeded, so release std::unique_ptr ownership of XAsyncBlock* because
    // the callback takes over ownership. If the call fails, however, std::unique_ptr keeps
    // ownership and deletes XAsyncBlock*.
    asyncBlock.release();
    downloadBlobBuffer.release();
}