delphi - 可以安全地假设 InternetCloseHandle() 不会失败，从而允许更清晰的代码吗？

Question

下面是使用 WinINet 执行 HTTP 请求并返回获取的字符串或引发异常的例程:

function Request(const pConnection: HINTERNET; const localpath: string): string;
var Buffer: packed Array[1..5000] of Char; BytesRead: Cardinal; pRequest: HINTERNET;     sent: boolean;
begin
Result := '';
pRequest := HTTPOpenRequest(pConnection, 'GET', pchar(localpath), nil, nil, nil, 0, 0);
if pRequest <> nil then
  begin
  sent := HTTPSendRequest(pRequest, nil, 0, nil, 0);
  if sent then
    while InternetReadFile(pRequest, @Buffer, SizeOf(Buffer)-1 {leave room for terminator}, BytesRead) do
      begin
      Buffer[BytesRead+1] := #0;
      Result := Result + buffer;
      end;
  InternetCloseHandle(pRequest);
  if not sent then RaiseLastOSerror; // HTTPSendRequest failed
  end
else RaiseLastOSerror; // HTTPOpenRequest failed
end;

如果即使已成功分配 pRequest，InternetCloseHandle(pRequest) 也可能失败，则 GetLastError() 将为 InternetCloseHandle() 而不是 HTTPSendRequest() 返回错误代码。修复这个问题需要如下代码:

function Request(const pConnection: HINTERNET; const localpath: string): string;
var Buffer: packed Array[1..5000] of Char; BytesRead: Cardinal; pRequest: HINTERNET;
begin
Result := '';
pRequest := HTTPOpenRequest(pConnection, 'GET', pchar(localpath), nil, nil, nil, 0, 0);
if pRequest <> nil then
  begin
  if HTTPSendRequest(pRequest, nil, 0, nil, 0) then
    while InternetReadFile(pRequest, @Buffer, SizeOf(Buffer)-1 {leave room for terminator}, BytesRead) do
      begin
      Buffer[BytesRead+1] := #0;
      Result := Result + buffer;
      end
  else
    begin
    InternetCloseHandle(pRequest);
    RaiseLastOSerror; // HTTPSendRequest failed
    end;
  InternetCloseHandle(pRequest);
  end
else RaiseLastOSerror; // HTTPOpenRequest failed
end;

但乍一看，这似乎更丑陋、更令人困惑。

可以安全地假设 InternetCloseHandle() 不会失败，从而允许更简单的代码吗？

Answer 1

首先，这种代码没有帮助:

raise Exception.Create(IntToStr(GetLastError))

改用这个:

RaiseLastOsError; // This raises an exception with the description of the error

既然您在代码中使用了异常，那么如何调用这样的函数，以便在无法关闭句柄时引发异常？

Win32Check(InternetCloseHandle(H))