| lock1 | ||
|---|---|---|
 | Chapter 4. SIMPOL Built-In Types |  |
lock1
Description
lock1 is an intrinsic object type, where objects can be
created using lock1.new() or by embedding.
lock1 objects are locked by threads, either as an
exclusive lock or a shared lock. This object is used to control access to
a resource (an object referenced via a variable) that may be shared by
more than one thread concurrently.
Type Tags
None
Object Value
The value of an object of type lock1 is undefined and it is an error to attempt to get or to set it.
lock1.new()
Description
A lock created using lock1.new() can be
pre-locked. This lock is exclusive and anonymous
in the sense that no thread holds the lock, but any thread can release
it. The return value is a reference to the new object. Embedded
lock1 objects are created without a lock.
Prototype
lock1.new (
boolean locked
Parameters
| Parameter | Default value | Type name | Description |
|---|---|---|---|
| locked | .false | boolean |
If this is equal to .true then the object is locked upon
creation.
|
Properties
| Property | Type | Description |
|---|---|---|
| _ | type(*) | This property is provided for use by the user to attach any object of any type to the type in which this property is provided. |
| __ | type(*) | This property is provided for use by the user to attach any object of any type to the type in which this property is provided. It has the additional feature of being marked with the resolve keyword, so that object resolution can continue down this property. |
| type | type | Specifies the lock1 type object. |
Methods
getexclusive()
Description
The lock will be acquired if no other thread has any lock on this object and
there is no anonymous lock on it. A thread can have any number of
exclusive locks on each lock1 object, but a single
exclusive lock by one thread prevents any sort of lock by any other
thread. A thread can have both exclusive and shared locks at the same
time. If no lock can be acquired immediately and the value of the
block parameter is .true then
the thread will not continue until the lock can be acquired. If the
lock can never be acquired because one or more other locks are held
by threads that cannot release them then the program halts with the
error number 73: deadly embrace. The return value is
.true or .false, indicating
whether or not the lock was acquired.
Prototype
lock1var.getexclusive (
boolean block
Parameters
| Parameter | Default value | Type name | Description |
|---|---|---|---|
| block | .true | boolean |
If the value of this parameter is .true then the thread
will block until it can acquire the exclusive lock.
|
getshared()
Description
The lock will be acquired if no other thread has an exclusive lock on this
object and there is no anonymous lock on it. A thread can have any
number of shared locks on each lock1 object, and
any number of threads can also hold shared locks on the same object
at the same time, but a single exclusive lock by one thread prevents
any shared lock by any other thread. A thread can have both exclusive
and shared locks at the same time. If no lock can be acquired
immediately and the value of the block parameter
is .true then the thread will not continue until
the lock can be acquired. If the lock can never be acquired because
one or more exclusive locks are held by threads that cannot release
them then the program halts with the error number 73: deadly embrace.
The return value is .true or
.false, indicating whether or not the lock was
acquired.
Prototype
lock1var.getshared (
boolean block
Parameters
| Parameter | Default value | Type name | Description |
|---|---|---|---|
| block | .true | boolean |
If the value of this parameter is .true then the thread
will block until it can acquire the shared lock.
|
release()
Description
This method releases the most recently acquired lock for this thread, or releases the anonymous lock granted at creation time of the lock1 object. If no lock exists that the current thread can release then a fatal error is raised.
Prototype
lock1var.release ()
Parameters
None