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The following language−defined packages exist:
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with System;package Ada.Interrupts is type Interrupt_ID is implementation−defined; type Parameterless_Handler is access protected procedure;
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This paragraph was deleted.
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function Is_Reserved (Interrupt : Interrupt_ID) return Boolean;
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function Is_Attached (Interrupt : Interrupt_ID) return Boolean;
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function Current_Handler (Interrupt : Interrupt_ID) return Parameterless_Handler;
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procedure Attach_Handler (New_Handler : in Parameterless_Handler; Interrupt : in Interrupt_ID);
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procedure Exchange_Handler (Old_Handler : out Parameterless_Handler; New_Handler : in Parameterless_Handler; Interrupt : in Interrupt_ID);
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procedure Detach_Handler (Interrupt : in Interrupt_ID);
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function Reference(Interrupt : Interrupt_ID) return System.Address;
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private ... −− not specified by the language end Ada.Interrupts;
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package Ada.Interrupts.Names is implementation−defined : constant Interrupt_ID := implementation−defined; . . . implementation−defined : constant Interrupt_ID := implementation−defined; end Ada.Interrupts.Names;
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The Interrupt_ID type is an implementation−defined discrete type used to identify interrupts.
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The Is_Reserved function returns True if and only if the specified interrupt is reserved.
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The Is_Attached function returns True if and only if a user−specified interrupt handler is attached to the interrupt.
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{8652/00698652/0069} {00166AI95−00166−01} The Current_Handler function returns a value that represents the attached handler of the interrupt. If no user−defined handler is attached to the interrupt, Current_Handler returns null.
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The Attach_Handler procedure attaches the specified handler to the interrupt, overriding any existing treatment (including a user handler) in effect for that interrupt. If New_Handler is null, the default treatment is restored. {Program_Error (raised by failure of run−time check)} If New_Handler designates a protected procedure to which the pragma Interrupt_Handler does not apply, Program_Error is raised. In this case, the operation does not modify the existing interrupt treatment.
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{8652/00698652/0069} {00166AI95−00166−01} The Exchange_Handler procedure operates in the same manner as Attach_Handler with the addition that the value returned in Old_Handler designates the previous treatment for the specified interrupt. If the previous treatment is not a user−defined handler, null is returned.
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Ramification: Calling Attach_Handler or Exchange_Handler with this value for New_Handler restores the previous handler.
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{8652/00698652/0069} {00166AI95−00166−01} If the application uses only parameterless procedures as handlers (other types of handlers may be provided by the implementation, but are not required by the standard), then if Old_Handler is not null, it may be called to execute the previous handler. This provides a way to cascade application interrupt handlers. However, the default handler cannot be cascaded this way (Old_Handler must be null for the default handler).
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The Detach_Handler procedure restores the default treatment for the specified interrupt.
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For all operations defined in this package that take a parameter of type Interrupt_ID, with the exception of Is_Reserved and Reference, a check is made that the specified interrupt is not reserved. {Program_Error (raised by failure of run−time check)} Program_Error is raised if this check fails.
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If, by using the Attach_Handler, Detach_Handler, or Exchange_Handler procedures, an attempt is made to detach a handler that was attached statically (using the pragma Attach_Handler), the handler is not detached and Program_Error is raised. {Program_Error (raised by failure of run−time check)} 22/2
{00434AI95−00434−01} The Reference function returns a value of type System.Address that can be used to attach a task entry via an address clause (see J.7.1) to the interrupt specified by Interrupt. This function raises Program_Error if attaching task entries to interrupts (or to this particular interrupt) is not supported. {Program_Error (raised by failure of run−time check)}
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At no time during attachment or exchange of handlers shall the current handler of the corresponding interrupt be undefined.
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{00434AI95−00434−01} If the Ceiling_Locking policy (see D.3) is in effect, the implementation shall document the default ceiling priority assigned to a protected object that contains either the Attach_Handler or Interrupt_Handler pragmas, but not the Interrupt_Priority pragma. [This default need not be the same for all interrupts.]
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Documentation Requirement: If the Ceiling_Locking policy is in effect, the default ceiling priority for a protected object that contains an interrupt handler pragma.
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If implementation−defined forms of interrupt handler procedures are supported, such as protected procedures with parameters, then for each such form of a handler, a type analogous to Parameterless_Handler should be specified in a child package of Interrupts, with the same operations as in the predefined package Interrupts.
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Implementation Advice: If implementation−defined forms of interrupt handler procedures are supported, then for each such form of a handler, a type analogous to Parameterless_Handler should be specified in a child package of Interrupts, with the same operations as in the predefined package Interrupts.
NOTES
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8 The package Interrupts.Names contains implementation−defined names (and constant values) for the interrupts that are supported by the implementation.
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Example of interrupt handlers:
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Device_Priority : constant array (1..5) of System.Interrupt_Priority := ( ... ); protected type Device_Interface (Int_ID : Ada.Interrupts.Interrupt_ID) is procedure Handler; pragma Attach_Handler(Handler, Int_ID); ... pragma Interrupt_Priority(Device_Priority(Int_ID)); end Device_Interface; ... Device_1_Driver : Device_Interface(1); ... Device_5_Driver : Device_Interface(5); ...
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{8652/00698652/0069} {00166AI95−00166−01} Corrigendum: Clarified that the value returned by Current_Handler and Exchange_Handler for the default treatment is null.