关于跨进程使用回调函数的研究：以跨进程获取Richedit中RTF流为例。

建议先参考我上次写的博文跨进程获取Richedit中Text：

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拿到这个问题，我习惯性地会从VCL内核开始分析。找到TRichEdit声明的单元，分析TRichEdit保存为RTF流的代码。（分析VCL内核代码方便了解Windows标准API的封装和使用） 打开声明TRichEdit的ComCtrls.pas单元。搜索"TRichEditStrings"（保存流使用TRichEdit.Lines.SaveToStream方法，TRichEditStrings为TRichEdit.Line的类型）
TRichEditStrings = class(TStrings)

private

RichEdit: TCustomRichEdit;

FPlainText: Boolean;

FConverter: TConversion;

procedure EnableChange(const Value: Boolean);

protected

function Get(Index: Integer): string; override;

function GetCount: Integer; override;

procedure Put(Index: Integer; const S: string); override;

procedure SetUpdateState(Updating: Boolean); override;

procedure SetTextStr(const Value: string); override;

public

destructor Destroy; override;

procedure Clear; override;

procedure AddStrings(Strings: TStrings); override;

procedure Delete(Index: Integer); override;

procedure Insert(Index: Integer; const S: string); override;

procedure LoadFromFile(const FileName: string); override;

procedure LoadFromStream(Stream: TStream); override;

procedure SaveToFile(const FileName: string); override;

procedure SaveToStream(Stream: TStream); override;

property PlainText: Boolean read FPlainText write FPlainText;

end; 寻找到SaveToStream的方法 procedure TRichEditStrings.SaveToStream(Stream: TStream); var EditStream: TEditStream;

TextType: Longint; StreamInfo: TRichEditStreamInfo; Converter: TConversion; begin if FConverter <> nil then Converter := FConverter else Converter := RichEdit.DefaultConverter.Create; StreamInfo.Stream
:= Stream; StreamInfo.Converter := Converter; try with EditStream do begin dwCookie := LongInt(Pointer(@StreamInfo)); pfnCallBack := @StreamSave; dwError := 0; end; if PlainText then TextType := SF_TEXT else
TextType := SF_RTF; SendMessage(RichEdit.Handle, EM_STREAMOUT, TextType, Longint(@EditStream)); if EditStream.dwError <> 0 then
raise EOutOfResources.Create(sRichEditSaveFail); finally if FConverter = nil then Converter.Free; end; end;

看关键的一句：“SendMessage(RichEdit.Handle, EM_STREAMOUT, TextType, Longint(@EditStream));” 这下明白了，获取RTF关键的是向Richedit发送EM_STREAMOUT消息。 关于EM_STREAMOUT消息想了解更多可以查阅MSDN：
EM_STREAMOUT wParam = (WPARAM) (UINT) uFormat; lParam = (LPARAM)
(EDITSTREAM FAR *) lpStream; 进程间的内存地址是相对的。 A进程$00450000内存地址值为34，那么B进程$00450000内存地址就不一定是34了。
在发送EM_STREAMOUT消息时，lParam参数表示的地址就是相对于目标进程的。 跨进程访问内存主要用到如下API函数： GetWindowThreadProcessId -- 根据窗体句柄获得其所在的线程、进程ID OpenProcess -- 打开进程并返回访问句柄 VirtualAllocEx -- 分配进程虚拟内存空间，返回所分配的内存地址。 VirtualFreeEx -- 释放进程虚拟内存空间 ReadProcessMemory、WriteProcessMemory -- 读写进程内存数据。
和以往不一样，这个消息用到了回调函数“pfnCallBack := @StreamSave;” 函数也是存放在内存中的数据（一些机器指令），访问函数同样会碰到进程间不能直接访问内存的问题。 也就是说：需要将函数数据写入到目标进程中，才能被正常调用。 【如何获得函数的数据？】

function MyFunction(A, B: Integer): Integer;

begin

Result := A + B;

end;

procedure TForm1.Button1Click(Sender: TObject);

begin

Edit1.Text := IntToStr(Integer(@MyFunction));

end; 函数地址容易得到。调试如上代码，点击按钮获得函数地址，打开CPU查看器（Ctrl+Alt+C），定位函数地址。 这样将看到如图：

03C2
--------add eax,edx

7105 --------jon +$05

E81f43FBFF --call @IntOver

C3 --------- ret 前面就是十六进制数据，后面就是该数据表示的机器指令。 这些就是函数数据，将它写入到目标进程就可以调用了！！！ 两个进程载入相同的DLL那么DLL的函数地址则是相同的，也就是说API函数SendMessage在A、B两个进程的地址一致。有了这点，利用系统API函数SendMessage发送WM_COPYDATA消息就可以交互数据了。 当然，如果指令里有相对地址的访问也得克隆才成，比如上面的"E81f43FBFF
--call @IntOver"就用到了相对地址。囧 可以将编译条件中“溢出、范围、IO"检查都关掉，减少相对地址的访问。 跨进程之前，先在本进程实验通过再说： 【第一个实验：正常调用回调函数】 function
MySendMessage(hWnd: HWND; Msg: UINT; wParam: WPARAM; lParam: LPARAM): LRESULT; stdcall;

begin

Result := SendMessage(hWnd, Msg, wParam, lParam);

end;

type

TMySendMessage = function (hWnd: HWND; Msg: UINT; wParam: WPARAM; lParam: LPARAM): LRESULT; stdcall;

var vMySendMessage: TMySendMessage = MySendMessage;

function EditStreamCallBack(dwCookie: Longint; pbBuff: PByte;

cb: Longint; var pcb: Longint): Longint; stdcall;

var

vCopyDataStruct: TCopyDataStruct;

begin

pcb := cb;

vCopyDataStruct.dwData := 0;

vCopyDataStruct.cbData := cb;

vCopyDataStruct.lpData := pbBuff;

vMySendMessage(dwCookie, WM_COPYDATA, 0, Integer(@vCopyDataStruct));

Result := ERROR_SUCCESS;

end;

procedure TForm1.Button3Click(Sender: TObject);

var

vEditStream: TEditStream;

begin

vEditStream.dwCookie := Handle;

vEditStream.dwError := 0;

vEditStream.pfnCallback := EditStreamCallBack;

FMemoryStream := TMemoryStream.Create;

SendMessage(RichEdit1.Handle, EM_STREAMOUT, SF_RTF, Integer(@vEditStream));

FMemoryStream.Position := 0;

Memo1.Lines.LoadFromStream(FMemoryStream);

FMemoryStream.Free;

end; “EditStreamCallBack“就是要复制到目标进程的函数数据。
调试通过后，获得其十六进制数据。

{ 55 } PUSH EBP { 8BEC } MOV EBP,ESP

{ 83C4F4 } ADD ESP,$F4

{ 8B4510 } MOV EAX,DWORD PTR [EBP+$10]

{ 8B5514 } MOV EDX,DWORD PTR [EBP+$14]

{ 8902 } MOV DWORD PTR [EDX],EAX

{ 33D2 } XOR EDX,EDX

{ 8955F4 } MOV DWORD PTR [EBP-$0C],EDX

{ 8945F8 } MOV DWORD PTR [EBP-$08],EAX

{ 8B450C } MOV EAX,DWORD PTR [EBP+$0C]

{ 8945FC } MOV DWORD PTR [EBP-$04],EAX

{ 8D45F4 } LEA EAX,DWORD PTR [EBP-$0C]

{ 50 } PUSH EAX

{ 6A00 } PUSH $00

{ 6A4A } PUSH $4A

{ 8B4508 } MOV EAX,DWORD PTR [EBP+$08]

{ 50 } PUSH EAX

{ FF15B88C4500} CALL DWORD PTR [$00458CB8]

{ 33C0 } XOR EAX,EAX

{ 8BE5 } MOV ESP,EBP

{ 5D } POP EBP

{ C21000 } RET $0010 其中{ FF15B88C4500} CALL DWORD PTR [$00458CB8]里的[$00458CB8] 里是相对地址，不同的调试环境会不一样。
我们这里[$00458CB8]里存放的就是系统API函数SendMessage的地址。 【第二个实验：拼装函数数据】 const

EditStreamCallBackBytes =

#$55 + // PUSH EBP

#$8B#$EC + // MOV EBP,ESP

#$83#$C4#$F4 + // ADD ESP,$F4

#$8B#$45#$10 + // MOV EAX,DWORD PTR [EBP+$10]

#$8B#$55#$14 + // MOV EDX,DWORD PTR [EBP+$14]

#$89#$02 + // MOV DWORD PTR [EDX],EAX

#$33#$D2 + // XOR EDX,EDX

#$89#$55#$F4 + // MOV DWORD PTR [EBP-$0C],EDX

#$89#$45#$F8 + // MOV DWORD PTR [EBP-$08],EAX

#$8B#$45#$0C + // MOV EAX,DWORD PTR [EBP+$0C]

#$89#$45#$FC + // MOV DWORD PTR [EBP-$04],EAX

#$8D#$45#$F4 + // LEA EAX,DWORD PTR [EBP-$0C]

#$50 + // PUSH EAX

#$6A#$00 + // PUSH $00

#$6A#$4A + // PUSH $4A

#$8B#$45#$08 + // MOV EAX,DWORD PTR [EBP+$08]

#$50 + // PUSH EAX

#$FF#$15#$00#$00#$00#$00 + // CALL DWORD PTR [H] -- String Index:43

#$33#$C0 + // XOR EAX,EAX

#$8B#$E5 + // MOV ESP,EBP

#$5D + // POP EBP

#$C2#$10#$00 + // RET $0010

#$00#$00#$00#$00 + // Api Address -- String Index:55

#$00#$00#$00#$00 + // _editstream : dwCookie -- String Index:59

#$00#$00#$00#$00 + // _editstream : dwError

#$00#$00#$00#$00; // _editstream : pfnCallback

type

TVclApi = packed record //JMP DWORD PTR [$HHHHHHHH]

rJmp: Word; // FF 25

rAddress: PInteger; // API实际地址

end;

PVclApi = ^TVclApi;

procedure TForm1.Button2Click(Sender: TObject);

type

PEditStream = ^TEditStream;

var

vEditStreamCallBack: string;

begin

vEditStreamCallBack := EditStreamCallBackBytes;

PInteger(@vEditStreamCallBack[43])^ := Integer(@vEditStreamCallBack[55]);

PInteger(@vEditStreamCallBack[55])^ := PVclApi(@SendMessage)^.rAddress^;

PEditStream(@vEditStreamCallBack[59])^.dwCookie := Handle;

PEditStream(@vEditStreamCallBack[59])^.pfnCallback := @vEditStreamCallBack[1];

FMemoryStream := TMemoryStream.Create;

SendMessage(RichEdit1.Handle, EM_STREAMOUT, SF_RTF, Integer(@vEditStreamCallBack[59]));

FMemoryStream.Position := 0;

Memo1.Lines.LoadFromStream(FMemoryStream);

FMemoryStream.Free;

end; VCL中调用API时使用JMP指令。 ”PVclApi(@SendMessage)^.rAddress^”就是获得SendMessage实际地址。 好了，本进程的实验做完后，我们就要拿另一个进程开刀了。
封装一下，最终代码如下：

uses RichEdit;

{$WARN SYMBOL_DEPRECATED OFF}

type
TRichEditStreamReader = class
private
FStream: TStream;
FHandle: THandle;
protected
procedure WndProc(var Message: TMessage); virtual;
public
constructor Create(AStream: TStream);
destructor Destroy; override;
property Handle: THandle read FHandle;
end;

{ TRichEditStreamReader }

constructor TRichEditStreamReader.Create(AStream: TStream);
begin
FStream := AStream;
FHandle := AllocateHWnd(WndProc);
end;

destructor TRichEditStreamReader.Destroy;
begin
DeallocateHWnd(FHandle);
inherited;
end;

procedure TRichEditStreamReader.WndProc(var Message: TMessage);
begin
case Message.Msg of
WM_COPYDATA:
begin
if not Assigned(FStream) then Exit;
FStream.Write(PCopyDataStruct(Message.LParam)^.lpData^,
PCopyDataStruct(Message.LParam)^.cbData);
end;
end;
end;

function Process_ReadRichEditStream(
AHandle: THandle; AStream: TStream; AFormat: Longword): Boolean;
type
TVclApi = packed record //JMP DWORD PTR [$HHHHHHHH]
rJmp: Word; // FF 25
rAddress: PInteger; // API实际地址
end;
PVclApi = ^TVclApi;
const
EditStreamCallBackBytes =
#$55 + //                     PUSH EBP
#$8B#$EC + //                 MOV EBP,ESP
#$83#$C4#$F4 + //             ADD ESP,$F4
#$8B#$45#$10 + //             MOV EAX,DWORD PTR [EBP+$10]
#$8B#$55#$14 + //             MOV EDX,DWORD PTR [EBP+$14]
#$89#$02 + //                 MOV DWORD PTR [EDX],EAX
#$33#$D2 + //                 XOR EDX,EDX
#$89#$55#$F4 + //             MOV DWORD PTR [EBP-$0C],EDX
#$89#$45#$F8 + //             MOV DWORD PTR [EBP-$08],EAX
#$8B#$45#$0C + //             MOV EAX,DWORD PTR [EBP+$0C]
#$89#$45#$FC + //             MOV DWORD PTR [EBP-$04],EAX
#$8D#$45#$F4 + //             LEA EAX,DWORD PTR [EBP-$0C]
#$50 + //                     PUSH EAX
#$6A#$00 + //                 PUSH $00
#$6A#$4A + //                 PUSH $4A
#$8B#$45#$08 + //             MOV EAX,DWORD PTR [EBP+$08]
#$50 + //                     PUSH EAX
#$FF#$15#$00#$00#$00#$00 + // CALL DWORD PTR [H] -- String Index:43
#$33#$C0 + //                 XOR EAX,EAX
#$8B#$E5 + //                 MOV ESP,EBP
#$5D + //                     POP EBP
#$C2#$10#$00 + //             RET $0010
#$00#$00#$00#$00 + //         Api Address -- String Index:55
#$00#$00#$00#$00 + //         _editstream : dwCookie -- String Index:59
#$00#$00#$00#$00 + //         _editstream : dwError
#$00#$00#$00#$00; //          _editstream : pfnCallback
type
PEditStream = ^TEditStream;
var
vEditStreamCallBack: string;
vProcessId: DWORD;
vProcess: THandle;
vPointer: Pointer;
vNumberOfBytesRead: Cardinal;
vRichEditStreamReader: TRichEditStreamReader;
begin
Result := False;
if not Assigned(AStream) then Exit;
if not IsWindow(AHandle) then Exit;
GetWindowThreadProcessId(AHandle, @vProcessId);
vProcess := OpenProcess(PROCESS_VM_OPERATION or PROCESS_VM_READ or
PROCESS_VM_WRITE, False, vProcessId);
try
vPointer := VirtualAllocEx(vProcess, nil, 4096, MEM_RESERVE or MEM_COMMIT,
PAGE_READWRITE);
vRichEditStreamReader := TRichEditStreamReader.Create(AStream);
try
vEditStreamCallBack := EditStreamCallBackBytes;
PInteger(@vEditStreamCallBack[43])^ := Integer(vPointer) + 55 - 1;
PInteger(@vEditStreamCallBack[55])^ := PVclApi(@SendMessage)^.rAddress^;
PEditStream(@vEditStreamCallBack[59])^.dwCookie := vRichEditStreamReader.Handle;
PEditStream(@vEditStreamCallBack[59])^.pfnCallback := vPointer;
WriteProcessMemory(vProcess, vPointer, @vEditStreamCallBack[1],
Length(vEditStreamCallBack), vNumberOfBytesRead);
SendMessage(AHandle, EM_STREAMOUT, AFormat, Integer(Integer(vPointer) + 59 - 1));
finally
vRichEditStreamReader.Free;
VirtualFreeEx(vProcess, vPointer, 0, MEM_RELEASE);
end;
finally
CloseHandle(vProcess);
end;
end; { Process_ReadRichEditStream }

procedure TForm1.Button1Click(Sender: TObject);
var
vHandle: THandle;
vMemoryStream: TMemoryStream;
begin
vHandle := FindWindow('WordPadClass', nil);
if vHandle = 0 then Exit;
vHandle := FindWindowEx(vHandle, 0, 'RICHEDIT50W', nil);
if vHandle = 0 then Exit;
vMemoryStream := TMemoryStream.Create;
try
Process_ReadRichEditStream(vHandle, vMemoryStream, SF_RTF);
vMemoryStream.Position := 0;
RichEdit1.PlainText := False;
RichEdit1.Lines.LoadFromStream(vMemoryStream);
finally
vMemoryStream.Free;
end;
end;