如何從沒有TThread的線程程序訪問類的成員？

Question

我有一個單元是這樣的

type 
TMyClass = Class(TObject) 
private 
AnInteger  : Integer; 
MyThreadHandle : DWORD; 
procedure MyPrivateProcedure; 
public 
procedure MyPublicProcedure; 
end; 

procedure TMyClass.MyPrivateProcedure; 
procedure MyThread; stdcall; 
begin 
    if AnInteger <> 0 then MyPublicProcedure; 
end; 
var 
DummyID: DWORD; 
begin 
    MyThreadHandle := CreateThread(NIL,0,@MyThread,NIL,0, DummyID); 
end; 

procedure TMyClass.MyPublicProcedure; 
begin 
AnInteger := 0; 
end; 

我的目標是有一個主題（無TTthread請。），可以「訪問」的瓦爾/功能/過程就像它是類的一部分。此示例失敗是因爲它無法訪問變量，也無法訪問該過程。這只是一個例子，我知道Integer不能像這樣改變。對我來說，擁有屬於課程一部分的線程非常重要。我也嘗試將整數作爲指針（工作）傳遞給線程，但我仍然無法訪問類的過程/函數。有任何想法嗎？

Answer 1

線程都有自己的堆棧指針，所以你不能訪問本地變量或參數（如隱藏的Self參數）在您的本地過程中（該函數聲明爲錯誤）。此外，如果它們從外部函數訪問變量（包括Self），則不能使用線程的本地過程。如果您將來要使用64位編譯器，則不能使用本地過程進行任何回調。

在你的情況下，你只需要修改你的過程的聲明並將它移到單元範圍中（使它成爲一個「獨立」過程，這允許你使用「Self」的線程回調參數）

function MyThread(MyObj: TMyClass): DWORD; stdcall; 
begin 
    if MyObj.AnInteger <> 0 then 
    MyObj.MyPublicProcedure; 
    Result := 0; 
end; 

procedure TMyClass.MyPrivateProcedure; 
var 
    DummyID: DWORD; 
begin 
    MyThreadHandle := CreateThread(nil, 0, @MyThread, Self, 0, DummyID); 
end; 

Answer 2

您可以使用TThread並保持較小的文件大小。我認爲你會走上一條艱難的道路：重新發明輪子非常耗時，我可以告訴你！ :)

下面是一些工作的代碼來初始化線程：

function ThreadProc(Thread: TThread): Integer; 
var FreeThread: Boolean; 
begin 
    if not Thread.FTerminated then 
    try 
    result := 0; // default ExitCode 
    try 
     Thread.Execute; 
    except 
     on Exception do 
     result := -1; 
    end; 
    finally 
    FreeThread := Thread.FFreeOnTerminate; 
    Thread.FFinished := True; 
    if Assigned(Thread.OnTerminate) then 
     Thread.OnTerminate(Thread); 
    if FreeThread then 
     Thread.Free; 
    EndThread(result); 
    end; 
end; 

constructor TThread.Create(CreateSuspended: Boolean); 
begin 
    IsMultiThread := true; // for FastMM4 locking, e.g. 
    inherited Create; 
    FSuspended := CreateSuspended; 
    FCreateSuspended := CreateSuspended; 
    FHandle := BeginThread(nil, 0, @ThreadProc, Pointer(Self), CREATE_SUSPENDED, FThreadID); 
    if FHandle = 0 then 
    raise Exception.Create(SysErrorMessage(GetLastError)); 
    SetThreadPriority(FHandle, THREAD_PRIORITY_NORMAL); 
end; 

也就是說，你傳遞對象爲pointer()線程創建API，這將作爲ThreadProc的獨特參數傳遞。

ThreadProc不應該是任何方法的一部分，而是全局的單元。

這裏是另一段代碼直接調用API來處理多線程壓縮，無開銷，並同步：

type 
    TThreadParams = record 
    bIn, bOut: pAESBlock; 
    BlockCount: integer; 
    Encrypt: boolean; 
    ID: DWORD; 
    AES: TAES; 
    end; 

{ we use direct Windows threads, since we don't need any exception handling 
    nor memory usage inside the Thread handler 
    -> avoid classes.TThread and system.BeginThread() use 
    -> application is still "officialy" mono-threaded (i.e. IsMultiThread=false), 
    for faster System.pas and FastMM4 (no locking) 
    -> code is even shorter then original one using TThread } 
function ThreadWrapper(var P: TThreadParams): Integer; stdcall; 
begin 
    with P do 
    AES.DoBlocks(bIn,bOut,bIn,bOut,BlockCount,Encrypt); 
    ExitThread(0); 
    result := 0; // make the compiler happy, but won't never be called 
end; 

procedure TAES.DoBlocksThread(var bIn, bOut: PAESBlock; Count: integer; doEncrypt: boolean); 
var Thread: array[0..3] of TThreadParams; // faster than dynamic array 
    Handle: array[0..3] of THandle; // high(Thread) is not compiled by XE2 
    nThread, i, nOne: integer; 
    pIn, pOut: PAESBlock; 
begin 
    if Count=0 then exit; 
    if {$ifdef USEPADLOCK} padlock_available or {$endif} 
    (SystemInfo.dwNumberOfProcessors<=1) or // (DebugHook<>0) or 
    (Count<((512*1024) div AESBlockSize)) then begin // not needed below 512 KB 
    DoBlocks(bIn,bOut,bIn,bOut,Count,doEncrypt); 
    exit; 
    end; 
    nThread := SystemInfo.dwNumberOfProcessors; 
    if nThread>length(Thread) then // a quad-core is enough ;) 
    nThread := length(Thread); 
    nOne := Count div nThread; 
    pIn := bIn; 
    pOut := bOut; 
    for i := 0 to nThread-1 do 
    with Thread[i] do begin // create threads parameters 
    bIn := pIn; 
    bOut := pOut; 
    BlockCount := nOne; 
    Encrypt := doEncrypt; 
    AES := self; // local copy of the AES context for every thread 
    Handle[i] := CreateThread(nil,0,@ThreadWrapper,@Thread[i],0,ID); 
    inc(pIn,nOne); 
    inc(pOut,nOne); 
    dec(Count,nOne); 
    end; 
    if Count>0 then 
    DoBlocks(pIn,pOut,pIn,pOut,Count,doEncrypt); // remaining blocks 
    inc(Count,nOne*nThread); 
    assert(integer(pIn)-integer(bIn)=Count*AESBlockSize); 
    assert(integer(pOut)-integer(bOut)=Count*AESBlockSize); 
    bIn := pIn; 
    bOut := pOut; 
    WaitForMultipleObjects(nThread,@Handle[0],True,INFINITE); 
    for i := 0 to nThread-1 do 
    CloseHandle(Handle[i]); 
end;