How much memory allocate when reading save blob with XGameSaveReadBlobData

Question

How much memory allocate when reading save blob with XGameSaveReadBlobData

Alekseev Maksim Valentinovich 0

I'm implementing game save logic and need to write a function that reads data from a single XGameSaveBlob. The documentation for XGameSaveReadBlobData explains how to use it, but it feels incomplete and even partially incorrect. For example, there’s no implementation of the _GetContainerBlobsDataSize method, which is supposed to define the amount of memory required.

I found what seems to be an implied implementation in another documentation page (XGameSaveEnumerateBlobInfo), but that doesn’t make sense — I don’t see why the value of sizeof(XGameSaveBlob) should be added to the allocated space.

Additionally, the documentation for XGameSaveBlobInfo states that XGameSaveBlobInfo::size represents the size of the XGameSaveBlob. However, when I look at the included header in my codebase, the comments there contradict the documentation.

struct XGameSaveBlobInfo
{
    _Field_z_ const char* name;  // unique blob name (unique to container)
    uint32_t size;           // size of the saved data
};
struct XGameSaveBlob
{
    XGameSaveBlobInfo info;  // metadata
    uint8_t* data;           // saved data
};

So my question is: what is the correct way to determine how much memory to allocate for a single XGameSaveBlob when reading, given these inconsistencies in the documentation?

2 answers

Your answer

Answer 1

To determine the correct amount of memory to allocate for a single XGameSaveBlob when reading, you should consider the following:

Size of the Blob Data: The XGameSaveBlobInfo::size field represents the size of the saved data within the blob. This is the primary value you will need to allocate memory for the actual data.
Size of the Blob Structure: You also need to account for the size of the XGameSaveBlob structure itself, which includes the XGameSaveBlobInfo metadata and the pointer to the data. Therefore, the total memory allocation should be the size of the blob data plus the size of the XGameSaveBlob structure.
Implementation Considerations: When implementing the function, you can calculate the total memory allocation as follows:
```
   size_t totalSize = sizeof(XGameSaveBlob) + blobInfo.size;
```
This ensures that you allocate enough memory for both the metadata and the actual saved data.

If you find discrepancies in the documentation or header comments, it may be helpful to cross-reference with other parts of the SDK or seek clarification from the documentation team or community forums. However, the approach outlined above should provide a solid basis for your memory allocation needs when reading from a XGameSaveBlob.

References:

Alekseev Maksim Valentinovich 0 Reputation points

2025-11-25T08:37:15.38+00:00

First, the current size calculation is incorrect because it doesn’t account for the memory required by the blob name. Second, there’s no real need to include the entire XGameSaveBlob structure in the calculation—only the size of the uint32_t field (which stores the blob data size) is relevant. In other words, the correct formula should be:

size of data + sizeof(uint32_t) + size of blob name + 1

Answer 2

Susmitha T (INFOSYS LIMITED) 1,630 Microsoft External Staff

Thank you for reaching out!

To correctly determine the memory allocation for a single XGameSaveBlob, you should account for the following components:

Blob Data Size Use XGameSaveBlobInfo::size to represent the actual saved data size.
Size Field Include sizeof(uint32_t) for storing the blob data size.
Blob Name Add strlen(blobInfo.name) + 1 to accommodate the blob name and its null terminator.

Correct formula: size_t totalSize = blobInfo.size // actual data

+ sizeof(uint32_t) // size field

Let me know if you need any further help with this. I will be happy to assist.

If you find this helpful, Kindly mark the provided solution as "Accept Answer", so that others in the community facing similar issues can easily find the solution. Your contribution is highly appreciated.

Alekseev Maksim Valentinovich 0 Reputation points

2025-11-26T09:17:38.79+00:00

Most likely this assumption is incorrect. I believe the provided implementation in documentation page XGameSaveEnumerateBlobInfo is correct, and we do need to allocate memory to account for the entire XGameSaveBlob. The reason is that we receive memory as a pointer to XGameSaveBlob, and we are expected to iterate over it. That implies we have objects of this type laid out in memory, so proper allocation is required.

It is most likely that the loaded data follows a format similar to:
| XGameSaveBlob objects (N times) | Actual data (blob contents, names) |
Susmitha T (INFOSYS LIMITED) 1,630 Reputation points Microsoft External Staff

2025-11-26T11:45:10.9366667+00:00

Thank you for your response.

Since you now have a clear understanding of how the XGameSaveBlob objects are structured in memory, this issue appears to be resolved.

Should you require further clarification or have any additional questions, please let me know. Otherwise, I will proceed to close this thread.
Susmitha T (INFOSYS LIMITED) 1,630 Reputation points Microsoft External Staff

2025-11-28T06:37:50.6+00:00

Hi, please let me know if you require further clarification or have any additional questions, please let me know. Otherwise, I will proceed to close this thread by 1st December.

Share via

How much memory allocate when reading save blob with XGameSaveReadBlobData

2 answers

Your answer