将FindScanline汇编代码转换为purepascal

Question

我试图将一些Delphi 5代码转换为Delphi XE7-x64,我仍然坚持以下代码:

function FindScanline(Source : Pointer; MaxLen : Cardinal;
  Value : Cardinal) : Cardinal; assembler;
asm
          PUSH    ECX
          MOV     ECX,EDX
          MOV     EDX,EDI
          MOV     EDI,EAX
          POP     EAX
          REPE    SCASB
          MOV     EAX,ECX
          MOV     EDI,EDX
end; 

据我所知,发生了以下事情:

push the contents of ECX register(Value) onto the stack
move contents of EDX register(MaxLen) into ECX register. now ECX holds (MaxLen)
move contents of EDI register into EDX register. now EDX holds (EDI) 
move contents of EAX register into EDI register. now EDI holds (Source)
pop ECX into EDX. now EDX holds (Value). Was (EDI) lost?
repeat while equal ?decrement ECX for each char?
move contents of ECX register into EAX register
move contents of EDX register into EDI register

对于参考函数,FindScanline用于函数GetCursorHeightMargin

任何有关翻译的帮助将不胜感激.

Answer 1

这是一个字面翻译:

function FindScanline(Source: Pointer; MaxLen: Cardinal; Value: Cardinal): Cardinal;
var
  Ptr: PByte;
begin
  Result := MaxLen;
  if Result > 0 then
    dec(Result);
  Ptr := Source;
  while (Result > 0) and (Ptr^ = Value) do
  begin
    inc(Ptr);
    dec(Result);
  end;
end;

不幸的是,处理边缘情况相当混乱.