Deallocating a Call
If an application is finished with a call and another application wants the
call, the call can be handed off. But if no other applications want to take
ownership, there is nothing to do but deallocate the call's handle. This is done
. A call handle is no longer valid after it has been deallocated.
In contrast, dropping (disconnecting) a call puts the call in the idle
state, which means that the local end of the connection is on hook. If the
other end of the connection drops the call, the call transitions to the disconnected
state, not the idle
state. Typically, once an application receives a call-state message
indicating the disconnected
state, it immediately drops the call, causing it to become idle
. Although the call is in the idle
state, any handles to it held by applications remain valid until they are
deallocated. If the call was never answered (the local end never went off hook),
it may revert to the idle
state without being dropped.
An application cannot deallocate a call if it is the sole owner and the call's
state is not idle
. This is because TAPI tries to ensure that there is always at least one owner
for every active call. If the application is the sole owner and the call is
, the error message LINEERR_INVALCALLSTATE is returned. If an application
needs to circumvent this restriction, it can do so by dropping the call first (with lineDrop
) and then deallocating its handle. This prevents an application from
deallocating its handle which would result in a call disconnect. By making the
application do an explicit drop, it can inform the user (in a dialog box) that the call
is about to be disconnected.
If releasing the ownership handle results in the call's having no more
handles, TAPI calls the service provider function TSPI_lineCloseCall
. When this function is invoked on a call that is not yet idle, it is up to
the service provider to drop the call.
An application that has monitor privileges for a call can always deallocate
its handle for the call. Deallocating a call does not affect the call state of
the physical call, but it does release the internal resources (memory) related
to the call.
An application should deallocate the handle to a call it owns in these two
- Idle call state. If an application receives a LINE_CALLSTATE message indicating that the call has transitioned to the idle state, and has already gathered all the information it needs about the call,
it should deallocate the call handle immediately.
- Handoff. The application has handed off the call (or has otherwise relinquished call
ownership to another application) or has set its call privilege to monitor, and
has no interest in monitoring or logging the call.
Failure to deallocate call handles in a timely way can result in system
failure and lost calls due to unnecessary consumption of memory and other resources.
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