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Downloading a blob from Title Storage

  • Článek

This topic demonstrates how to download a blob from Xbox services Title Storage by using the following flat C code example.

Notes about XblTitleStorageDownloadBlobAsync parameters

  • The buffer that you provide to store the downloaded blob data must be large enough to store the blob that's being downloaded. If you need to, you can retrieve the length that's required for the buffer by getting the blob metadata.

  • This API returns E_NOT_SUFFICIENT_BUFFER (0x8007007A) if blobBuffer doesn't have enough capacity to hold the blob data.

  • To use the default size, pass 0 for preferredDownloadBlockSize.

Flat C

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();
}

See also

XAsyncBlock

XblTitleStorageDownloadBlobAsync

XblTitleStorageDownloadBlobResult

XblTitleStorageETagMatchCondition