DownloadBuffer with HTTPRange return unexpected number of written bytes

[tamir-laminar]

Bug Report

• Bug in the following releases :
• • github.com/Azure/azure-sdk-for-go/sdk/storage/azblob/ - 1.5.0
• • github.com/Azure/azure-sdk-for-go/sdk/storage/azfile/ - 1.4.0

res := make([]byte, 100)
n, err := blobClient.DownloadBuffer(ctx, res, &blob.DownloadBufferOptions{
	Range: blob.HTTPRange{
		Offset: 0,
		Count:  100,
	},
})
fmt.Println(res[:n]) // n is always 100, even if the file has less them 100 bytes, so we get garbage.

If the file have less then requested Count, it should return the number of bytes that were actually written to the buffer (the variable n in that example).
instead it always return the Count, meaning that if we pass the Count in the range option, n is always equals to Count.

It's a problem since we don't now how to slice the response in order to get the actual data without garbage.

The above also true for azfile library.

What I expected

DownloadBuffer(ctx context.Context, buffer []byte, o *DownloadBufferOptions) (int64, error)

DownloadBuffer should return the number of bytes that were actually written to the buffer.

[github-actions]

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

[tanyasethi-msft]

Hi @tamir-laminar ,
Thanks for reporting this, we are looking into this issue and will get back to you soon