sc_lock.3

读写Smart卡加解密接口的程序

.TH sc_lock 3 "April 2003" "OpenSC Programmer's Manual
.SH NAME
sc_lock, sc_unlock \- lock or unlock smart card
.SH SYNOPSIS
.nf
.B #include <opensc.h>
.sp
.BI "int sc_lock(sc_card_t *" card ");
.BI "int sc_unlock(sc_card_t *" card ");
.fi
.SH DESCRIPTION
These functions handle locking of smart cards, in order to prevent
concurrent access to the same card by different users.
.PP
Locking is important to prevent unauthorized access to the card
after presenting the PIN, for instance.
.PP
After a call to \fBsc_lock\fP, concurrent access by other application
to the same smart card reader is disallowed, provided the reader
middleware supports this (see below). A lock must later be released
by calling \fBsc_unlock\fP. When disconnecting from the card using
\fBsc_disconnect_card\fP, there must not be anymore locks on the
card.
.PP
Calls to \fBsc_lock\fP may be nested, i.e. if \fBsc_lock\fP is called
five times in a row, the lock will not be released until the fifth
call to \fBsc_unlock\fP.
.PP
Note that these functions do not offer mutual exclusion for different
threads within the same application process. Multithread locking is
the application's job (Note that the OpenSC PKCS11 module provides
MT locking facilities, as that's part of the standard).
.SH NOTES
Whether locking is effective depends a lot on the middleware
used to talk to the card reader. CTAPI based drivers for instance
perform no interprocess locking at all.
.PP
The only middleware implementation currently used by OpenSC that
does perform this type of locking is PCSC.
.SH RETURN VALUE
If an error occurred, a negative error code is returned, as described
in \fbsc_error\fP(3). Otherwise, the function will return 0.
.SH SEE ALSO
.BR sc_connect_card (3).
.SH AUTHOR
This manual page was written by Olaf Kirch <[e-mail]>