Delphi 高效读写锁

Posted 2020-07-03 子航

本人设计了一个高效读写锁，可实现多个线程读一个线程写的锁，应该比Delphi自带的读写锁高效，本人没有做对比测试。

本文的锁不可以在一个线程里重入，否则会锁死，另外读写锁最多支持65535个线程同时读。

//[email protected]
//跨平台简易高效锁

unit uLocker;

interface

type
  //多读单写锁
  //1.写的时候阻塞其他所有写和读
  //2.读的时候不阻塞其他读，但阻塞所有写，当阻塞了一个或以上的写后，将阻塞所有后来新的读
  TMultiReadSingleWriteLocker = class
    FLocker: Integer;
    procedure LockRead;
    procedure UnLockRead;
    procedure LockWrite;
    procedure UnLockWrite;
    function TryLockRead:Boolean;
    function TryLockWrite:Boolean;
    constructor Create;
  end;

  TSimpleLocker=class
    FLocker:Integer;
    procedure Lock;
    procedure UnLock;
    function TryLock:Boolean;
  end;

implementation

uses System.SyncObjs, System.SysUtils;

{ TMultiReadSingleWriteLocker }

procedure TMultiReadSingleWriteLocker.LockWrite;
begin
  if TInterLocked.Add(FLocker, $10000) <> $10000 then
  begin
    while (TInterLocked.Add(FLocker, 0) and $FFFF) <> $10000 do
      Sleep(0);
  end;
end;

function TMultiReadSingleWriteLocker.TryLockRead: Boolean;
begin
  Result:=TInterLocked.Increment(FLocker) and $FFFF0000 =0;
  if not Result then
     TInterLocked.Decrement(FLocker)
end;

function TMultiReadSingleWriteLocker.TryLockWrite: Boolean;
begin
  Result:=TInterLocked.Add(FLocker, $10000) = $10000;
end;

procedure TMultiReadSingleWriteLocker.UnLockWrite;
begin
  TInterLocked.Add(FLocker, -$10000);
end;

procedure TMultiReadSingleWriteLocker.UnLockRead;
begin
    TInterLocked.Decrement(FLocker);
end;

constructor TMultiReadSingleWriteLocker.Create;
begin
  FLocker:=0;
end;

procedure TMultiReadSingleWriteLocker.LockRead;
begin
  if TInterLocked.Increment(FLocker) and $FFFF0000 <> 0 then
  begin
    while TInterLocked.Add(FLocker, 0) and $FFFF0000 <> 0 do
      Sleep(0);
  end;
end;

{ TSimpleLocker }

procedure TSimpleLocker.Lock;
begin
  while TInterLocked.CompareExchange(FLocker, 1, 0)<>0 do
    Sleep(0);
end;

function TSimpleLocker.TryLock: Boolean;
begin
  Result:= TInterLocked.CompareExchange(FLocker, 1, 0)=0;
end;

procedure TSimpleLocker.UnLock;
begin
  TInterLocked.CompareExchange(FLocker, 0, 1);
end;

end.