Ada Reference Manual (Ada 2022) — Legal Information

C.6.4 The Package System.Atomic_Operations.Integer_Arithmetic

The language-defined generic package System.Atomic_Operations.Integer_Arithmetic provides operations to perform arithmetic atomically on objects of integer types.

Static Semantics

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The generic library package System.Atomic_Operations.Integer_Arithmetic has the following declaration:

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generic
type Atomic_Type is range <> with Atomic;
package System.Atomic_Operations.Integer_Arithmetic
with Pure, Nonblocking is

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   procedure Atomic_Add (Item  : aliased in out Atomic_Type;
                         Value : Atomic_Type)
      with Convention => Intrinsic;

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   procedure Atomic_Subtract (Item  : aliased in out Atomic_Type;
                              Value : Atomic_Type)
      with Convention => Intrinsic;

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   function Atomic_Fetch_And_Add
     (Item  : aliased in out Atomic_Type;
      Value : Atomic_Type) return Atomic_Type
      with Convention => Intrinsic;

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   function Atomic_Fetch_And_Subtract
     (Item  : aliased in out Atomic_Type;
      Value : Atomic_Type) return Atomic_Type
      with Convention => Intrinsic;

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function Is_Lock_Free (Item : aliased Atomic_Type) return Boolean
with Convention => Intrinsic;

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end System.Atomic_Operations.Integer_Arithmetic;

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The operations of this package are defined as follows:

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procedure Atomic_Add (Item  : aliased in out Atomic_Type;
                      Value : Atomic_Type)
   with Convention => Intrinsic;

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Atomically performs: Item := Item + Value;

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procedure Atomic_Subtract (Item  : aliased in out Atomic_Type;
                           Value : Atomic_Type)
   with Convention => Intrinsic;

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Atomically performs: Item := Item - Value;

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function Atomic_Fetch_And_Add
  (Item  : aliased in out Atomic_Type;
   Value : Atomic_Type) return Atomic_Type
   with Convention => Intrinsic;

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Atomically performs: Tmp := Item; Item := Item + Value; return Tmp;

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function Atomic_Fetch_And_Subtract
  (Item  : aliased in out Atomic_Type;
   Value : Atomic_Type) return Atomic_Type
   with Convention => Intrinsic;

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Atomically performs: Tmp := Item; Item := Item - Value; return Tmp;

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