[英]Thread-safe way to increment and return an integer in Delphi
In a single-threaded application I use code like this: 在单线程应用程序中,我使用如下代码:
Interface
function GetNextUID : integer;
Implementation
function GetNextUID : integer;
const
cUID : integer = 0;
begin
inc( cUID );
result := cUID;
end;
This could of course be implemented as a singleton object, etc. - I'm just giving the simplest possible example. 这当然可以作为单个对象实现,等等 - 我只是给出了最简单的例子。
Q: How can I modify this function (or design a class) to achieve the same result safely from concurrent threads? 问:如何修改此函数(或设计类)以从并发线程安全地实现相同的结果?
You can use the Interlocked*
functions: 您可以使用Interlocked*
功能:
function GetNextUID : integer;
{$J+} // Writeble constants
const
cUID : integer = 0;
begin
Result := InterlockedIncrement(cUID);
end;
More modern Delphi versions have renamed these methods into Atomic*
(like AtomicDecrement
, AtomicIncrement
, etc), so the example code becomes this: 更现代的Delphi版本已将这些方法重命名为Atomic*
(如AtomicDecrement
, AtomicIncrement
等),因此示例代码变为:
function GetNextUID : integer;
{$J+} // Writeble constants
const
cUID : integer = 0;
begin
Result := AtomicIncrement(cUID);
end;
最简单的方法可能就是调用InterlockedIncrement
来完成这项工作。
With modern Delphi compilers it is better to use Increment function of class TInterlocked from unit System.SyncObjs. 使用现代Delphi编译器,最好从System.SyncObjs单元使用TInterlocked类的Increment函数。 Something like this: 像这样的东西:
type
TMyClass = class
class var
FIdCounter: int64;
var
FId: int64;
constructor Create;
end;
constructor TMyClass.Create;
begin
FId := TInterlocked.Increment(FIdCounter);
end;
This helps to keep the code platform-independent. 这有助于保持代码平台无关。
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