delphi - 将 FindScanline 汇编代码转换为 purepascal

Question

我正在尝试将一些 Delphi 5 代码转换为 Delphi XE7-x64，但我陷入了以下代码:

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; 

据我了解，正在发生以下事情:

push the contents of ECX register(Value) onto the stackmove 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 registermove contents of EDX register into EDI register

引用函数FindScanline用于函数 GetCursorHeightMargin

任何翻译上述内容的帮助将不胜感激。

Answer 1

这是直译:

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，处理边缘情况相当困惑。