A.18.28 The Generic Package Containers.Unbounded_Synchronized_Queues
Static Semantics
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The language-defined generic package Containers.Unbounded_Synchronized_Queues
provides type Queue, which implements the interface type Containers.Synchronized_Queue_Interfaces.Queue.2/3
with System;
with Ada.Containers.Synchronized_Queue_Interfaces;
generic
with package Queue_Interfaces is new Ada.Containers.Synchronized_Queue_Interfaces (<>);
Default_Ceiling : System.Any_Priority := System.Priority'Last;
package Ada.Containers.Unbounded_Synchronized_Queues is
pragma Preelaborate(Unbounded_Synchronized_Queues);
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package Implementation is
... -- not specified by the language
end Implementation;
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protected type Queue
(Ceiling: System.Any_Priority := Default_Ceiling)
with Priority => Ceiling is
new Queue_Interfaces.Queue with
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overriding
entry Enqueue (New_Item : in Queue_Interfaces.Element_Type);
overriding
entry Dequeue (Element : out Queue_Interfaces.Element_Type);
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overriding
function Current_Use return Count_Type;
overriding
function Peak_Use return Count_Type;
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private
... -- not specified by the language
end Queue;
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private
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... -- not specified by the language
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end Ada.Containers.Unbounded_Synchronized_Queues;
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The type Queue is used to represent task-safe queues.12/3
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The capacity for instances of type Queue is unbounded.12.a/3
Ramification: Enqueue
never blocks; if more storage is needed for a new element, it is allocated
dynamically. We don't need to explicitly specify that Queue needs finalization,
because it is visibly protected.
12.b/3
Discussion: Nested
package Implementation can be used to declare the types needed to implement
the protected type Queue. This nested package is necessary as types cannot
be declared in the private part of a protected type, and the types have
to be declared within the generic unit in order to depend on the types
imported with package Queue_Interfaces. Clients should never depend on
the contents of nested package Implementation.
Extensions to Ada 2005
12.c/3
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AI05-0159-1}
The generic package Containers.Unbounded_Synchronized_Queues
is new.
Ada 2005 and 2012 Editions sponsored in part by Ada-Europe
