(宽)字符串 – 存储在TFileStream,Delphi 7中.最快的方法是什么

procedure WriteWideString(const ws: WideString; stream: TStream);
var
  nChars: LongInt;
begin
  nChars := Length(ws);
  stream.WriteBuffer(nChars,SizeOf(nChars);
  if nChars > 0 then
    stream.WriteBuffer(ws[1],nChars * SizeOf(ws[1]));
end;

function ReadWideString(stream: TStream): WideString;
var
  nChars: LongInt;
begin
  stream.ReadBuffer(nChars,SizeOf(nChars));
  SetLength(Result,nChars);
  if nChars > 0 then
    stream.ReadBuffer(Result[1],nChars * SizeOf(Result[1]));
end;

现在,从技术上讲,由于WideString是Windows BSTR,它可以包含奇数个字节. Length函数读取字节数并除以2,因此可能(尽管不太可能)上面的代码将切断最后一个字节.您可以使用此代码：

procedure WriteWideString(const ws: WideString; stream: TStream);
var
  nBytes: LongInt;
begin
  nBytes := SysStringByteLen(Pointer(ws));
  stream.WriteBuffer(nBytes,SizeOf(nBytes));
  if nBytes > 0 then
    stream.WriteBuffer(Pointer(ws)^,nBytes);
end;

function ReadWideString(stream: TStream): WideString;
var
  nBytes: LongInt;
  buffer: PAnsiChar;
begin
  stream.ReadBuffer(nBytes,SizeOf(nBytes));
  if nBytes > 0 then begin
    GetMem(buffer,nBytes);
    try
      stream.ReadBuffer(buffer^,nBytes);
      Result := SysAllocStringByteLen(buffer,nBytes)
    finally
      FreeMem(buffer);
    end;
  end else
    Result := '';
end;

受到Mghie’s answer的启发,用ReadBuffer和WriteBuffer替换了我的Read和Write调用.如果后者无法读取或写入请求的字节数,则会引发异常.