OpenCard Framework 1.2 Programmer's Guide - OpenSCDP

}
}
// do something with the wanted terminal
// ...
} catch OpenCard Exceptions {
// handle exception
// ...
}
Once you have the reference to the wanted terminal, you can either use the
application-driven model and wait for a card using the SmartCard’s waitForCard()
method to pass it a CardRequest object with the card terminal set (by means of the
setCardTerminal() method), or you can use the event-driven model and get the
card using the SmartCard’s getSmartCard() method to pass it the
CardTerminalEvent object you received via the cardInserted() notification.
Gaining exclusive access to the smart card
Referencing files
Exclusive access to smart cards can be required in situations where an application
needs to perform a semantic function on the card that requires an uninterrupted
sequence of smart card operations. A good example for this requirement is a
payment application such as running in an automatic teller machine (ATM) 11 that
has to debit the card and credit some account (or vice versa) by a certain amount
within a transaction context.
In your applications, you can acquire a mutex context by calling the beginMutex()
method and release it by calling endMutex() on the SmartCard object. For the
application to be well-behaved, you should claim the mutex context for as short a
period as possible to avoid unnecessarily blocking other applications (or threads)
from accessing the card.
ISO-1716-4 defines four different ways of referencing files within a smart card.
They are:
Referencing by file identifier:
Files may be referenced by a file identifier coded in two bytes. For
uniqueness, EFs (files) and DFs (directories) under a common DF shall
have different file identifiers. The MF (root directory) shall have a file ID of
hexadecimal value 0x3f00.
Referencing by path:
Files may referenced by a path, i.e. a concatenation of file identifiers. The
path begins with the identifier of the MF or of the current DF, the order of
the identifiers is parent to child. In case the identifier of the current
directory is unknown, a hexadecimal value of 0x3fff can be used instead
(reserved value).
Referencing by short EF identifier:
EFs can be referenced by a short EF identifier coded on five bits with
values in the range from 1 to 30. The value 0 is used to reference the
currently selected EF. Short EF identifiers cannot be used in a path or as a
file ID.
11. ATM’s typically take in the cards for the period of interaction to prevent early removal of the card by the user.
Chapter 5. Advanced programming with OCF 35