Fix integer overflow in TDSWriter.writeString()

[micheljung]

Fixes GH-1530

[peterbae]

@micheljung could you add a test case to show that this fix will solve the issue?

[micheljung]

@peterbae I can but this will require generating a string that uses 1GiB of memory. Is that something you're ok with having in your unit tests?

[peterbae]

I was hoping we could host the file somewhere, since the standard procedure for pushing a fix to our repository requires some form of testing (to make sure the fix is intended). However, I think this fix is pretty straightforward, so I think we don't need a test case for this one. We will review and merge this soon.

[micheljung]

The file wouldn't need to be hosted, the string can be generated. My question is whether you want a unit test that consumes 1 GiB of heap just for a single string :)

[peterbae]

No, I think it would be ok without the test this time.

[lilgreenbird]

/azp run Microsoft.mssql-jdbc.macOS

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