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owndevunit.doc
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1994-11-17
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TABLE OF CONTENTS
OwnDevUnit.library/AttemptDevUnit
OwnDevUnit.library/AvailDevUnit
OwnDevUnit.library/FreeDevUnit
OwnDevUnit.library/LockDevUnit
OwnDevUnit.library/NameDevUnit
OwnDevUnit.library/AttemptDevUnit May 25, 1991 23:05
NAME
AttemptDevUnit --- Attempt to lock a device/unit
SYNOPSIS
Failure = AttemptDevUnit( Device, Unit, OwnerName , NotifyBit );
d0 a0 d0 a1 d1.b
UBYTE *Failure;
UBYTE *Device;
ULONG Unit;
UBYTE *OwnerName;
UBYTE NotifyBit;
FUNCTION
This function will attempt to lock the specified device/unit. It will
wait a maximum of five seconds for the device/unit to become free.
This delay is to allow an owner that has requested notification to get
off the device when the attempt is made. This function is intended
for interactive use where blocking indefinitely is undesirable.
INPUTS
Device
A pointer to the name of the device you wish to lock.
Unit
The unit number of the device you wish to lock.
OwnerName
A pointer to a name returned to the caller of AttemptDevUnit()
when you refuse to give up the lock to someone else.
NotifyBit
Some programs, such as Getty, sit on a device waiting for a call
to come in. It is to their advantage to know when someone else
wants the device so that they can release the lock. This would
allow someone to use a term program, for instance, and not have to
specifically shut down the program sitting on the device.
If you wish to be notified when someone tries to lock the de-
vice/unit you own, pass a signal bit number, as returned by
AllocSignal(), in this argument. When someone tries to lock the
device/unit, your task will be signaled. Passing a zero in this ar-
gument indicates that you do not wish to be notified when someone
requests the device.
RETURNS
If the device/unit is successfully locked, NULL is returned. If
someone else owns the device, a pointer to their OwnerName is re-
turned. If an internal error occurred, a pointer to an error message
is returned.
All error messages begin with ODUERR_LEADCHAR. This allows one to
quickly check if the returned value is an error message or owner name.
The possible errors are:
ODUERR_NOMEM -- An out of memory condition occurred while attempting
to lock the device.
ODUERR_NOTIMER -- The timer.device could not be opened while attempt-
ing to lock the device.
ODUERR_BADNAME -- An invalid device name was supplied. This occurs
only when Device is NULL.
ODUERR_BADBIT -- An invalid notify bit was supplied. This occurs
only when NotifyBit equals -1.
ODUERR_UNKNOWN -- Not strictly an error. This occurs when the lock
could not be granted, but the name of the current
owner is NULL.
BUGS
None know.
SEE ALSO
LockDevUnit(), exec.library/AllocSignal()
OwnDevUnit.library/AvailDevUnit May 25, 1991 23:05
NAME
AvailDevUnit --- Quickly check the availability of a device/unit
SYNOPSIS
Truth = AvailDevUnit( Device, Unit);
d0 a0 d0
BOOL Truth;
UBYTE *Device;
ULONG Unit;
FUNCTION
This function will quickly determine if a device/unit is currently
available (i.e., not locked). It does not perform a lock. It is
intended for cases where one must wait for a device/unit to become
free, but because of the nature of the code, waiting the five seconds
AttempDevUnit() takes to return is undesirable.
INPUTS
Device
A pointer to the name of the device you wish to check.
Unit
The unit number of the device you wish to check.
RETURNS
If the device/unit is currently available, TRUE is returned. If it is
currently locked, FALSE is returned.
BUGS
None known.
SEE ALSO
AttemptDevUnit()
OwnDevUnit.library/FreeDevUnit May 25, 1991 23:05
NAME
FreeDevUnit --- Release a lock on a device/unit
SYNOPSIS
FreeDevUnit(Device , Unit);
a0 d0
UBYTE *Device;
ULONG Unit;
FUNCTION
Releases a lock on a device/unit previously attained by a call to
AttemptDevUnit() or LockDevUnit(). This function must be called
from the same task context that the lock was attained under or the
device/unit will not be freed!
INPUTS
Device
A pointer to the name of the device you wish to release.
Unit
The unit number of the device you wish to release.
RETURNS
None.
BUGS
None known.
SEE ALSO
AttemptDevUnit(), FreeDevUnit()
OwnDevUnit.library/LockDevUnit May 25, 1991 23:05
NAME
LockDevUnit --- Block until a lock on a device/unit is granted
SYNOPSIS
Failure = LockDevUnit( Device, Unit, OwnerName , NotifyBit );
d0 a0 d0 a1 d1.b
UBYTE *Failure;
UBYTE *Device;
ULONG Unit;
UBYTE *OwnerName;
UBYTE NotifyBit;
FUNCTION
This function will block until a lock on the specified device/unit is
granted. It is intended for non-interactive use.
INPUTS
Device
A pointer to the name of the device you wish to lock.
Unit
The unit number of the device you wish to lock.
OwnerName
A pointer to a name returned to the caller of AttemptDevUnit()
when you refuse to give up the lock to someone else.
NotifyBit
Some programs, such as Getty, sit on a device waiting for a call
to come in. It is to their advantage to know when someone else
wants the device so that they can release the lock. This would
allow someone to use a term program, for instance, and not have to
specifically shut down the program sitting on the device.
If you wish to be notified when someone tries to lock the de-
vice/unit you own, pass a signal bit number, as returned by
AllocSignal(), in this argument. When someone tries to lock the
device/unit, your task will be signaled. Passing a zero in this ar-
gument indicates that you do not wish to be notified when someone
requests the device.
RETURNS
If the device/unit is successfully locked, NULL is returned. If an
internal error occurred, a pointer to an error message is returned.
All error messages begin with ODUERR_LEADCHAR. This allows one to
quickly check if the returned value is an error message or owner name.
The possible errors are:
ODUERR_NOMEM -- An out of memory condition occurred while attempting
to lock the device.
ODUERR_NOTIMER -- The timer.device could not be opened while attempt-
ing to lock the device.
ODUERR_BADNAME -- An invalid device name was supplied. This occurs
only when Device is NULL.
ODUERR_BADBIT -- An invalid notify bit was supplied. This occurs
only when NotifyBit equals -1.
BUGS
None know.
SEE ALSO
AttemptDevUnit(), exec.library/AllocSignal()
OwnDevUnit.library/NameDevUnit May 25, 1991 23:05
NAME
NameDevUnit --- Change the owner name value of a locked device/unit
SYNOPSIS
NameDevUnit(Device , Unit, OwnerName );
a0 d0 a1
UBYTE *Device;
ULONG Unit;
UBYTE *OwnerName;
FUNCTION
This allows one to change the owner name returned by AttemptDevUnit().
You must own the lock on the specified device/unit or t