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# BlockRange

A structure that represents a range of blocks.

```
struct BlockRange;
```

## Discussion

The pure virtual function `_DoAsyncUnmap`, which your dext must implement, takes this type as a parameter that indicates the blocks to unmap.

## Topics

### Accessing Block Range Properties

[`uint64_t startBlock;`](/documentation/BlockStorageDeviceDriverKit/BlockRange/startBlock)

The address of the first block in this range.

[`uint64_t numOfBlocks;`](/documentation/BlockStorageDeviceDriverKit/BlockRange/numOfBlocks)

The number of blocks in this range.


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