JCL Help:LockedCompareExchange@Int64@Int64@Int64
JCL Help: LockedCompareExchange Function
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Summary
Thread safe compare and exchange.
Pascal
function LockedCompareExchange(var Target: Integer; Exch: Integer; Comp: Integer): Integer; overload;
function LockedCompareExchange(var Target: TObject; Exch: TObject; Comp: TObject): TObject; overload;
function LockedCompareExchange(var Target: Pointer; Exch: Pointer; Comp: Pointer): Pointer; overload;
function LockedCompareExchange(var Target: Int64; Exch: Int64; Comp: Int64): Int64; overload;
Parameters
| Parameters | Description |
| var Target: Integer | The target variable to compare Value and which conditionally receives the value of Exch. |
| Exch: Integer | The value which is moved into Target if Comp and Target are equal. |
| Comp: Integer | The comperand which Target is compared against. |
Return Value
The value of Target on procedure entry. Depending on the comparison, Target may have been updated or have retained its value.
Description
LockedCompareExchange compares Comp with Target. If they are equal the value of Exch is moved into Target, otherwise Target retains its value. All this is performed in a locked, thread-safe manner. The LockedXxx functions allow for a simple and efficient way for applications to synchronize access to and manipulate integer variables which are shared by multiple threads.
See Also
LockedExchangeSub LockedExchange LockedExchangeInc LockedExchangeDec
About
Unit
Donator
Azret Botash
Notes
The Win32 API provides similar functions. Look up InterlockedXxx in the Platform SDK.
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