delphi – 假设InternetCloseHandle()不会失败,从而允许更清晰的
发布时间:2020-12-15 09:19:32 所属栏目:大数据 来源:网络整理
导读:这是使用WinINet执行HTTP请求的例程,并返回获取的字符串或引发异常: function Request(const pConnection: HINTERNET; const localpath: string): string;var Buffer: packed Array[1..5000] of Char; BytesRead: Cardinal; pRequest: HINTERNET; sent: boo
这是使用WinINet执行HTTP请求的例程,并返回获取的字符串或引发异常:
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,0); if pRequest <> nil then begin sent := HTTPSendRequest(pRequest,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; 如果即使成功分配了pRequest,InternetCloseHandle(pRequest)也可能失败,GetLastError()将返回InternetCloseHandle()而不是HTTPSendRequest()的错误代码.修复需要以下代码: 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,0); if pRequest <> nil then begin if HTTPSendRequest(pRequest,0) then while InternetReadFile(pRequest,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; 但这看起来更加丑陋,乍一看更加令人困惑. 假设InternetCloseHandle()不会失败,从而允许更简单的代码是否安全? 解决方法
我认为你这是错误的方式.您应该只检查每个API调用的错误,并在遇到异常时立即引发异常.这样您就会得到适合于产生异常的错误的错误消息.您根本无法期望继续调用其他API函数,然后针对前一段时间发生的错误引发异常.
我想你想要这样的东西: Result := ''; pRequest := HTTPOpenRequest(pConnection,0); if pRequest=nil then RaiseLastOSerror; try CheckWin32Error(HTTPSendRequest(pRequest,0)); while InternetReadFile(pRequest,SizeOf(Buffer)-1,BytesRead) do begin Buffer[BytesRead+1] := #0; Result := Result + buffer; end; if GetLastError<>0 then RaiseLastOSerror; finally CheckWin32Error(InternetCloseHandle(pRequest)); end; 请注意,您没有包含InternetReadFile的任何错误检查.我试图为你写. (编辑:李大同) 【声明】本站内容均来自网络,其相关言论仅代表作者个人观点,不代表本站立场。若无意侵犯到您的权利,请及时与联系站长删除相关内容! |