[BUG] PageBlobWriteStream advances stream position twice during write

[andreaskoepf]

Describe the bug
When a write-stream for a CloudPageBlob is created with OpenWrite() and data is written to the StorageWriteStream the stream's position is internally incremented twice. The two additions happen: 1. in the base class StorageWriterStream here and in 2. the derived PageBlobWriteStream here.

Expected behavior
The number of bytes written should be added only to the stream position 1x and not 2x for each write.

What is the actual behavior?
The reported stream position after a write is too high (the offset is added twice, see source code references above).

To Reproduce

1. Create a PageBlobWriteStream object via CloudPageBlob.OpenWrite()
2. Read stream's Position property
3. Write 512 bytes of data into the stream
4. Read stream's Position property again and observe that it now is 1024 higher than before

Environment:

• Azure.Storage.Blobs 12.5.1
• Windows 10, Microsoft.NETCore.App 3.1.7
• VS 2019 v16.7.2

[jsquire]

Thank you for your feedback. Tagging and routing to the team best able to assist.

[ghost]

Thanks for the feedback! We are routing this to the appropriate team for follow-up. cc @xgithubtriage.

[seanmcc-msft]

Note that this is for the V11 library.

[andreaskoepf]

@seanmcc-msft You mean V12, don't you? At least the versions of Azure.Storage.Blobs and Azure.Storage.Common that I used to reproduce the bug locally both were 12.5.1 and the source files to which I refer are both part of a commit that was merged 16 days ago.

[seanmcc-msft]

Yes this is V12, I was confused by the references to CloudPageBlob, which is a class from V11, and not present in V12.

[andreaskoepf]

@seanmcc-msft sorry for the confusion, I was indeed porting/updating old code to the new sdk. I should have written PageBlobClient of course and not CloudPageBlob...