- Static Semantics
- 1
- The following language-defined packages exist:
- 2
- with System;
package Ada.Interrupts is
type Interrupt_ID is implementation-defined;
type Parameterless_Handler is
access protected procedure;
- 3
-
- 4
- function Is_Reserved (Interrupt : Interrupt_ID)
return Boolean;
- 5
- function Is_Attached (Interrupt : Interrupt_ID)
return Boolean;
- 6
- function Current_Handler (Interrupt : Interrupt_ID)
return Parameterless_Handler;
- 7
- procedure Attach_Handler
(New_Handler : in Parameterless_Handler;
Interrupt : in Interrupt_ID);
- 8
- procedure Exchange_Handler
(Old_Handler : out Parameterless_Handler;
New_Handler : in Parameterless_Handler;
Interrupt : in Interrupt_ID);
- 9
- procedure Detach_Handler
(Interrupt : in Interrupt_ID);
- 10
- function Reference(Interrupt : Interrupt_ID)
return System.Address;
- 11
- private
... -- not specified by the language
end Ada.Interrupts;
- 12
- package Ada.Interrupts.Names is
implementation-defined : constant Interrupt_ID :=
implementation-defined;
. . .
implementation-defined : constant Interrupt_ID :=
implementation-defined;
end Ada.Interrupts.Names;
- Dynamic Semantics
- 13
- The Interrupt_ID type is an implementation-defined discrete type used to identify interrupts.
- 14
- The Is_Reserved function returns True if and only if the specified interrupt is reserved.
- 15
- The Is_Attached function returns True if and only if a user-specified interrupt handler is attached to the interrupt.
- 16
- 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 a value that designates the default treatment; calling Attach_Handler or Exchange_Handler with this value restores the default treatment.
- 17
- 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. 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.
- 18
- 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.
- 18.a
- Ramification: Calling Attach_Handler or Exchange_Handler with this value for New_Handler restores the previous handler.
- 19
- The Detach_Handler procedure restores the default treatment for the specified interrupt.
- 20
- 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 is raised if this check fails.
- 21
- 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.
- 22
- 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.
- Implementation Requirements
- 23
- At no time during attachment or exchange of handlers shall the current handler of the corresponding interrupt be undefined.
- Documentation Requirements
- 24
- 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.]
- Implementation Advice
- 25
- 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.
- NOTES
- 26 8
- The package Interrupts.Names contains implementation-defined names (and constant values) for the interrupts that are supported by the implementation.
- Examples
- 27
- Example of interrupt handlers:
- 28
- 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);
...