Reliable connection on all platforms

[martinpaljak]

I want to get a "reliable" connection to the smart card. Right now there is an option to specify either shared or exclusive access to a reader during connect(). Exclusive access is the best option, but it is not always possible in real life situations - some other system app keeps a an idle connection to the reader open, for example. For such situations SCard(Begin|End)Transaction could be used, together with a shared connection.

This is sometimes worse than a plain shared connection, as Windows 8+ have a "5 second rule" for transactions (see Remarks in MSDN: https://msdn.microsoft.com/en-us/library/windows/desktop/aa379469(v=vs.85).aspx)

There are at least two paths to a solution:

• expose SCard*Transaction calls on JS API level. This leaves the burden of transaction management to the app developer
• hide the complexity from app developer and add an option to connect() that would indicate "shared mode transactions", which would call SCardBeginTransaction on non-windows platforms, together with SCardConnect. And give a synthesized SCARD_E_SHARING_VIOLATION error if this fails for some reason.

From flexibility POV, the first option would be best, from ease of use and 'DWIM' interface POV, I would probably wrap the exposed transaction mechanism behind a connect() wrapper before use, anyway.